Re: [geo] Wind and wave energies are not renewable after all

[Govindasamy bala]

Hi David,

Couple of questions.
Generation of wind energy would increase the KE dissipation rate but this is
not an external forcing to the climate system. I agree there would be local
and regional climate changes but there should be no global mean warming.
Right?

The current KE dissipation rate is about 2 watts/m^2. Over land, this
translates to about 300 TW. Suppose wind farms extract 150 TW (which may be
impractical), the dissipation rate over land will increase to 3 Wm^2. Don't
you think the KE (or available PE) generation rate in the atmosphere would
correspondingly increase? Of course these would be large regional climate
changes.

Bala

On Tue, Jul 12, 2011 at 8:37 AM, David Keith  wrote:

> Responding to a VERY old thread on wind power:
>
> ** **
>
> *The only link to geoengineering here is that there is a possibility of
> manipulating wind turbine drag for weather control, see: *
>
> ** **
>
> At 10’s TW scale extraction of wind does begin to be constrained by the
> generation of kinetic energy. I led the a joint NCAR-GFDL group that
> published the first paper on this topic see: 
>
> David W. Keith et al, The influence of large-scale wind-power on global
> climate. *Proceedings of the National* *Academy* *of Sciences*, *101*, p.
> 16115-16120.
>
> http://people.ucalgary.ca/~keith/papers/66.Keith.2004.WindAndClimate.e.pdf
> 
>
> ** **
>
> See
> http://people.ucalgary.ca/~keith/papers/94.Kirk-Davidoff.SurfaceRoughnessJAS.p.pdffor
>  a paper that says a bit about why it happens.
> 
>
> ** **
>
> The following web page gives and overview but it’s now out of date:
> http://people.ucalgary.ca/~keith/wind.html
>
> ** **
>
> Alvia’s comment that about “kinetic energy, i.e. the motion of molecules”,
> confuses the physics. Kinetic energy is *macroscopic* velocity, random
> motion of molecules is just heat. It is true that large scale production and
> dissipation of kinetic energy must balance, have a look at Peixoto and
> Oort’s the *Physics of Climate* or a short encyclopedia article I one
> wrote on atmospheric energetics:
> http://people.ucalgary.ca/~keith/papers/15.Keith.1996.Energetics.s.pdf ***
> *
>
> ** **
>
> Bottom lines:
>
> ** **
>
> 1. Commonly cited estimates for global wind power potential are too large.
> On cannot get to 100 TW in any practical scheme I know about. 
>
> ** **
>
> 2. At even a few TW large scale climate effects will begin to be important.
> But, this does not say we should not make a few TW of wind, just that--like
> any energy technology—there are tradeoffs.
>
> ** **
>
> David
>
> ** **
>
> *From:* geoengineering@googlegroups.com [mailto:
> geoengineering@googlegroups.com] *On Behalf Of *Nando
> *Sent:* Saturday, April 02, 2011 8:25 AM
> *To:* agask...@nc.rr.com
> *Cc:* andrew.lock...@gmail.com; geoengineering
> *Subject:* Re: [geo] Wind and wave energies are not renewable after all***
> *
>
> ** **
>
> My reading of the article suggested that the authors of the study were
> principally claiming that wind has an impact on climate, so it is already
> being "used". What wasn't clear from the article was *what type* of impact
> reducing the energy level of winds all over the globe through the prolific
> use of wind turbines might have. In a warming world, I understand we should
> expect stronger winds. On a simplistic generalized level that might not be
> relevant to local climate, slowing those stronger winds down might have
> an ameliorating effect on climate change. Hence the claim that "*The
> magnitude of the changes was comparable to the changes to the climate caused
> by doubling atmospheric concentrations of carbon dioxide*" might not be as
> bad as it is made to seem.
>
> ** **
>
> As usually, I'm grasping at straws, but as a layman, that's what stood out
> for me.
>
> ** **
>
> Nando
>
> On Sat, Apr 2, 2011 at 3:15 PM, Alvia Gaskill  wrote:*
> ***
>
> Wind and wave energy are the result of the conversion of solar energy into
> kinetic energy, i.e. the motion of molecules.  Once converted into kinetic
> energy it's a use it or lose it proposition.  Extracting kinetic energy from
> the atmosphere or the ocean doesn't mean it won't be replaced by more energy
> from sunlight.  Planting more trees will also intercept winds, albeit
> without the electricity generation.  Who funded this research?  The same
> people who want to prevent contact with alien civilizations?  I note that
> the Royal Society was also a party to that one too.  Note to Royal Society.
> When you actually find something under the bed I should be afraid of, wake
> me up.
>
> - Original Message - 
>
> *From:* Andrew Lockley  
>
> *To:* geoengineering  
>
> *Sent:* Friday, April 01, 2011 8:10
>
> *Subject:* [geo] Wind and wave energies are not renewable after all
>
> ** **
> Wind and wave energies are not renewable after all
>
> **· **30 March 2011 by *Mark 
> Buchanan*

[geo]

[Govindasamy bala]

Anyone has a copy of this report? Can I get a pdf?

Aines, R. and Friedmann, J., 2008. Enabling Cost Effective CO2 Capture
Directly From the Atmosphere, Lawrence Livermore National Laboratory,
Livermore, CA, USA

Thanks,

-- 

Best wishes,

---
Dr. G. Bala
Associate Professor
Center for Atmospheric and Oceanic Sciences
Indian Institute of Science
Bangalore - 560 012
India

Tel: +91 80 2293 3428
+91 80 2293 2075
Fax: +91 80 2360 0865
+91 80 2293 3425
Email: gb...@caos.iisc.ernet.in
 bala@gmail.com
Web:http://caos.iisc.ernet.in/faculty/gbala/gbala.html
---

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Re: [geo] Charitable donations for geoengineering research

[Govindasamy Bala]

I (Indian Institute of Science) would be happy to receive funds to do
research in geoengineering science (modeling).
Bala

On Fri, Jan 13, 2012 at 5:00 AM, Andrew Lockley wrote:

> It would be useful, as a matter of record, to have on this list any
> institutions which currently accept donations specifically earmarked for
> geoengineering science or policy research.
>
> At present it is unclear to me if any labs or organisations are able to
> accept donations from members of the public.
>
> I'm sure that there are many legitimate uses for such funds - eg funding
> PhDs, buying computer time, journal page fees, conference sponsorship,
> delegate travel bursaries.
>
> Could anyone who has details of such an opportunity for donations please
> reply to the list?
>
> A
>
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> http://groups.google.com/group/geoengineering?hl=en.
>



-- 
Best wishes,

---
Dr. G. Bala
Associate Professor
Center for Atmospheric and Oceanic Sciences
Indian Institute of Science
Bangalore - 560 012
India

Tel: +91 80 2293 3428
+91 80 2293 2075
Fax: +91 80 2360 0865
+91 80 2293 3425
Email: gb...@caos.iisc.ernet.in
 bala@gmail.com
Web:http://caos.iisc.ernet.in/faculty/gbala/gbala.html
---

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Re: [geo] tropospheric aerosol use

[Govindasamy Bala]

"Climate changes" by Budyko, on page 244, discusses why tropospheric
aerosols are not as effective as stratospheric aerosols for climate
modification.
1) life time is only a couple of weeks
2) Particle size becomes too big quickly and hence not effective for
scattering
3) Presence of clouds make them less effective
4) absorption by aerosols of near IR shortwave could partially cancel the
cooling by scattering.

Bala
On Thu, Mar 15, 2012 at 9:53 PM, Nathan Currier wrote:

> Does anyone know of any published papers exploring the use of
> tropospheric aerosol use?
>
> cheers,
>
> Nathan
>
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>
>


-- 
Best wishes,

---
Dr. G. Bala
Associate Professor
Center for Atmospheric and Oceanic Sciences
Indian Institute of Science
Bangalore - 560 012
India

Tel: +91 80 2293 3428
+91 80 2293 2075
Fax: +91 80 2360 0865
+91 80 2293 3425
Email: gb...@caos.iisc.ernet.in
 bala@gmail.com
Web:http://caos.iisc.ernet.in/faculty/gbala/gbala.html
---

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Re: [geo] Re: paper showing that "turning down the sun" experiments have similar climate results to "prescribed stratospheric aerosol" experiments

[Govindasamy Bala]

>>> warming in the 90s. They also noted:
>>>
>>> Current global climate models simulate lower-stratospheric temperature
>>> trends poorly, and even up-to-date stratospheric chemistry-climate models
>>> do not consistently reproduce tropical tropopause minimum temperatures or
>>> recently observed changes in stratospheric water vapor.
>>>
>>>
>>>
>>> Their paper only dealt with changes in one of the two ways that the
>>> stratosphere gets its water vapor, but I’ve often wondered about the
>>> potential impacts of sulfur SRM on the other one – that is, stratospheric
>>> methane. Solomon et al, while suggesting that methane’s role is relatively
>>> weak in H2O creation near the tropopause (where it apparently counts most
>>> for surface warming), noted:
>>>
>>> Estimates of the forcing due to (stratospheric) methane oxidation have
>>> varied widely among different studies, perhaps because of different shapes
>>> of the water profile in the region of greatest sensitivity.
>>>
>>>
>>> One of my questions has been whether prolonged use of stratospheric
>>> sulfur SRM, unlike the sudden pulse of a volcano, could potentially give
>>> rise to analogous “competitive” reactions to those seen in the troposphere
>>> involving sulfur chemistry and methane hydroxylation (i.e., Shindell et al
>>> 2007, 2009, 2012, etc), one of the factors that have driven our assumed
>>> increase in the indirect forcing effects of methane over the last half
>>> decade.
>>>
>>> I wonder, if additions of sulfur did actually lead, at the decadal scale
>>> of the methane lifetime, to increases in stratospheric H2O, what could its
>>> maximum impact be? What percentage of all stratospheric H2O comes from
>>> methane, in the first place? Does current SRM modeling account for such
>>> possible interactions?
>>>
>>> Best,
>>>
>>> Nathan
>>>
>>>
>>>
>>> *Solomon et al 2010:
>>>
>>>
>>>
>>> abstract
>>> http://www.sciencemag.org/content/327/5970/1219.abstract
>>>
>>> full paper
>>> http://www.climate.unibe.ch/~plattner/papers/solomon10sci.pdf
>>>
>>> discussions of, from NOAA & RealClimate:
>>> http://www.noaanews.noaa.gov/stories2010/20100128_watervapor.html
>>>
>>> http://www.realclimate.org/index.php/archives/2010/01/
>>> the-wisdom-of-solomon/
>>>
>>>
>>>
>>> On Friday, July 25, 2014 11:39:52 AM UTC-4, kcaldeira wrote:
>>>
>>>> Folks,
>>>>
>>>> Andrew wrote something the other day about "turning down the sun"
>>>> experiments NOT being a good analogue for stratospheric aerosol
>>>> geoengineering.
>>>>
>>>> Of course, what tool you use depends on your goals in using a tool. The
>>>> attached paper shows results indicating that for many purposes, "turning
>>>> down the sun" is a clear and efficient way of simulating many aspects of
>>>> solar geoengineering.
>>>>
>>>> If you are looking at effects on the stratosphere or looking at effects
>>>> of diffuse radiation, then you would need to simulate aerosols, but if you
>>>> are just trying to get an idea of temperature and hydrological changes,
>>>> then it seems that "turning down the sun" does a pretty good job.
>>>>
>>>> Enjoy,
>>>>
>>>> Ken
>>>>
>>>>
>>>> http://link.springer.com/article/10.1007/s00382-014-2240-3
>>>>
>>>>
>>>>
>>>> *Modeling of solar radiation management: a comparisonof simulations
>>>> using reduced solar constant and stratospheric sulphate aerosols*
>>>>
>>>> Sirisha Kalidindi · Govindasamy Bala ·
>>>> Angshuman Modak · Ken Caldeira
>>>>
>>>>
>>>> Abstract The climatic effects of Solar Radiation Management
>>>> (SRM) geoengineering have been often modeled
>>>> by simply reducing the solar constant. This is most likely
>>>> valid only for space sunshades and not for atmosphere and
>>>> surface based SRM methods. In this study, a global climate
>>>> model is used to evaluate the differences in the climate
>>>> response to SRM by uniform solar constant reduction and
>>>> stratospheric aerosols. Our analysis shows that when global
>>

[geo] ACP paper: Assessing the effects of varying the meridional distribution of aerosols in SRM

[Govindasamy Bala]

This following paper is published in ACP today. The main focus is on the
hydrological impacts of varying the latitudinal distribution of a FIXED
amount of  aerosols. Sensitivity of simulated climate to latitudinal
distribution of solar insolation reduction in solar radiation management
A. Modak and G. Bala
Divecha Centre for Climate Change {&} Centre for Atmospheric and Oceanic
Sciences, Indian Institute of Science, Bangalore, 560 012, India

Abstract. Solar radiation management (SRM) geoengineering has been proposed
as a potential option to counteract climate change. We perform a set of
idealized geoengineering simulations using Community Atmosphere Model
version 3.1 developed at the National Center for Atmospheric Research to
investigate the global hydrological implications of varying the latitudinal
distribution of solar insolation reduction in SRM methods. To reduce the
solar insolation we have prescribed sulfate aerosols in the stratosphere.
The radiative forcing in the geoengineering simulations is the net forcing
from a doubling of CO2 and the prescribed stratospheric aerosols. We find
that for a fixed total mass of sulfate aerosols (12.6 Mt of SO4), relative
to a uniform distribution which nearly offsets changes in global mean
temperature from a doubling of CO2, global mean radiative forcing is larger
when aerosol concentration is maximum at the poles leading to a warmer
global mean climate and consequently an intensified hydrological cycle.
Opposite changes are simulated when aerosol concentration is maximized in
the tropics. We obtain a range of 1 K in global mean temperature and 3% in
precipitation changes by varying the distribution pattern in our
simulations: this range is about 50% of the climate change from a doubling
of CO2. Hence, our study demonstrates that a range of global mean climate
states, determined by the global mean radiative forcing, are possible for a
fixed total amount of aerosols but with differing latitudinal distribution.
However, it is important to note that this is an idealized study and thus
not all important realistic climate processes are modeled.


-- 
Best wishes,

---
G. Bala
Professor
Center for Atmospheric and Oceanic Sciences
Indian Institute of Science
Bangalore - 560 012
India

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[geo] Deforestation and Precipitation changes in Monsoonal regions

[Govindasamy Bala]

This PNAS paper by my team highlights the importance of understanding the
atmospheric circulation changes to better characterize rainfall changes.
The paper has relevance to geoengineering discussions because both climate
change and geoengineering have the potential to cause circulation changes
in the atmosphere.

http://www.pnas.org/content/early/2015/02/23/1423439112.abstract


*Effects of large-scale deforestation on precipitation inthe monsoon
regions: Remote versus local effects*

N. Devaraju1, Govindasamy Bala, and Angshuman Modak

Divecha Center for Climate Change & Center for Atmospheric and Oceanic
Sciences, Indian Institute of Science, Bangalore 560012, India


Abstract
In this paper, using idealized climate model simulations, we investigate
the biogeophysical effects of large-scale deforestation
on monsoon regions. We find that the remote forcing from largescale
deforestation in the northern middle and high latitudes
shifts the Intertropical Convergence Zone southward. This results
in a significant decrease in precipitation in the Northern Hemisphere
monsoon regions (East Asia, North America, North Africa, and South
Asia) and moderate precipitation increases in the Southern Hemisphere
monsoon regions (South Africa, South America, and Australia).
The magnitude of the monsoonal precipitation changes depends on
the location of deforestation, with remote effects showing a larger
influence than local effects. The South Asian Monsoon region is
affected the most, with 18% decline in precipitation over India. Our
results indicate that any comprehensive assessment of afforestation/
reforestation as climate change mitigation strategies should carefully
evaluate the remote effects on monsoonal precipitation alongside the
large local impacts on temperatures.


-- 
With Best Wishes,

---
G. Bala
Professor
Center for Atmospheric and Oceanic Sciences
Indian Institute of Science
Bangalore - 560 012
India

Tel: +91 80 2293 3428; +91 80 2293 2505
Fax: +91 80 2360 0865; +91 80 2293 3425
Email: gb...@caos.iisc.ernet.in; bala@gmail.com
Web:http://caos.iisc.ernet.in/faculty/gbala/gbala.html
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[geo] Sensitivity of simulated climate to latitudinal distribution of solar insolation reduction in SRM geoengineering methods

[Govindasamy Bala]

Here is A discussion Paper on geoengineering in Atmospheric Chemistry and
Physics that came out today

Sensitivity of simulated climate to latitudinal distribution of solar
insolation reduction in SRM geoengineering methods

A. Modak and G. Bala
Divecha Centre for Climate Change & Centre for Atmospheric and Oceanic
Sciences, Indian
Institute of Science, Bangalore – 560 012, India

Abstract
Solar radiation management (SRM) geoengineering has been proposed as a
potential option to counteract climate change. We perform a set of
idealized geoengineering simulations to understand the global hydrological
implications of varying the latitudinal distribution of solar insolation
reduction in SRM methods. We find that for a fixed to tal mass of sulfate
aerosols (12.6Mt of SO4), relative to a uniform distribution which
mitigates changes in global mean temperature, global mean radiative forcing
is larger when aerosol concentration is maximum at the poles leading to a
warmer global mean climate and consequently an intensified hydrological
cycle. Opposite changes are simulated when aerosol concentration is
maximized in the tropics. We obtain a range of 1K in global mean
temperature and 3% in precipitation changes by varying the distri-
bution pattern: this range is about 50% of the climate change from a
doubling of CO2. Hence, our study demonstrates that a range of global mean
climate states, determined by the global mean radiative forcing, are
possible for a fixed total amount of aerosols but with differing
latitudinal distribution, highlighting the need for a careful
evaluation ofSRM proposals

-- 
Best wishes,

---
Dr. G. Bala
Associate Professor
Center for Atmospheric and Oceanic Sciences
Indian Institute of Science
Bangalore - 560 012
India

Tel: +91 80 2293 3428
+91 80 2293 2075
Fax: +91 80 2360 0865
+91 80 2293 3425
Email: gb...@caos.iisc.ernet.in
 bala@gmail.com
Web:http://caos.iisc.ernet.in/faculty/gbala/gbala.html
---

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Re: [geo] Fwd: Hiatus in global mean T trends

[Govindasamy Bala]

Dear All,

The discussion on "Hiatus" in global warming by me is posted now on a
regular webpage at

http://www.dccc.iisc.ernet.in/hiatus_gbala.html

of course a pdf can be downloaded from there...

Best wishes,
Bala




On Sat, Sep 28, 2013 at 3:34 PM, Andrew Lockley wrote:

> Posted at Bala's request.
>
> A
>  -- Forwarded message --
> From: "Govindasamy Bala" 
> Date: Sep 28, 2013 7:23 AM
> Subject: Hiatus in global mean T trends
> To: "Andrew Lockley" 
> Cc:
>
> Hi Andrew,
>
> I have a brief discussion on the possible causes for this hiatus as well
> some recommendation on what metric could be used in climate change
> discussions to avoid confusion and controversies.
>
> http://www.dccc.iisc.ernet.in/Trends-T-ver3.pdf
>
> Would be great if you can post this to the geoengineering email list.
>
> --
> Best wishes,
>
> ---
> Dr. G. Bala
> Associate Professor
> Center for Atmospheric and Oceanic Sciences
> Indian Institute of Science
> Bangalore - 560 012
> India
>
> Tel: +91 80 2293 3428
> +91 80 2293 2075
> Fax: +91 80 2360 0865
> +91 80 2293 3425
> Email: gb...@caos.iisc.ernet.in
>  bala@gmail.com
> Web:http://caos.iisc.ernet.in/faculty/gbala/gbala.html
> ---
>
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>



-- 
Best wishes,

---
Dr. G. Bala
Associate Professor
Center for Atmospheric and Oceanic Sciences
Indian Institute of Science
Bangalore - 560 012
India

Tel: +91 80 2293 3428
+91 80 2293 2075
Fax: +91 80 2360 0865
+91 80 2293 3425
Email: gb...@caos.iisc.ernet.in
 bala@gmail.com
Web:http://caos.iisc.ernet.in/faculty/gbala/gbala.html
---

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Re: [geo] Plan to avert global warming by cooling planet artificially 'could cause climate chaos' - The Independent

[Govindasamy Bala]

Dear All,

The last sentence in the abstract is misleading: "This effect is not
captured when geoengineering is modelled as a reduction in total solar
irradiance, suggesting caution is required when interpreting model results
from solar dimming experiments as analogues for stratospheric aerosol
geoengineering."

The authors have not used the same spatial pattern of SRM forcing in the
two cases. While uniform reduction in solar irradiance is used in solar
constant reduction experiment, magnitude of the solar irridance reduction
is maximized in the tropical areas in the aerosol SRM. Hence the result
that you get more rainfall reduction in tropical areas in the aerosol SRM
is obvious. Basically the paper is comparing apples to oranges.

This type of media hype based on obvious results would not lead us too far.



On Thu, Jan 9, 2014 at 9:54 AM, Greg Rau  wrote:

> Further comment here:
> http://www.commondreams.org/headline/2014/01/08-4
>
> Greg
>
>
>   --
>  *From:* Angus Ferraro 
> *To:* geoengineering@googlegroups.com
> *Cc:* andrew.lock...@gmail.com; Angus Ferraro 
> *Sent:* Wednesday, January 8, 2014 4:24 AM
> *Subject:* Re: [geo] Plan to avert global warming by cooling planet
> artificially 'could cause climate chaos' - The Independent
>
> Hi all,
>
> I think the media spin wasn't ideal as well. The paper took a while to
> appear on the ERL website but it's up now (though only in PDF form - the
> HTML form is not working as yet). Here's the link:
> http://iopscience.iop.org/1748-9326/9/1/014001/pdf/1748-9326_9_1_014001.pdf
>
> Abstract
> Geoengineering by injection of reflective aerosols into the stratosphere
> has been proposed as a way to counteract the warming effect of greenhouse
> gases by reducing the intensity of solar radiation reaching the surface.
> Here, climate model simulations are used to examine the effect of
> geoengineering on the tropical overturning circulation. The strength of the
> circulation is related to the atmospheric static stability and has
> implications for tropical rainfall. The tropical circulation is projected
> to weaken under anthropogenic global warming. Geoengineering with
> stratospheric sulfate aerosol does not mitigate this weakening of the
> circulation. This response is due to a fast adjustment of the troposphere
> to radiative heating from the aerosol layer. This effect is not captured
> when geoengineering is modelled as a reduction in total solar irradiance,
> suggesting caution is required when interpreting model results from solar
> dimming experiments as analogues for stratospheric aerosol geoengineering.
>
> Cheers
>
> Angus
>
> On Wednesday, 8 January 2014 10:07:51 UTC, matthew watson wrote:
>
> Hi all,
>
> I liked the paper (I did not review it for the journal but was asked to
> provide comment for the media). I did not like the press release or the
> 'spin' at all. Whilst I am not a fan of SRM particularly, the 'nail in the
> coffin' framing doesn't quite convince me. The paper was a model run of 4 X
> CO2 (1020 ppm) and 5 X Pinatubo (I assume using 20 MT SO2 for that, so 150
> MT sulphate). That, to me, is a little like saying 'this car failed it's
> safety test after I dropped it from 30,000 ft'.I don't doubt that rainfall
> would be affected, we saw that after Pinatubo (and other eruptions). Here's
> what Piers Forster and I wrote...
>
> *Dr Matt Watson**, Senior Lecturer in Natural Hazards at the University
> of Bristol, **said:*
> "The paper draws two conclusions.  Firstly, models that simply dim the
> Sun as an approximation for global cooling by aerosols do a poor job of
> capturing rainfall changes compared with those that model stratospheric
> aerosols explicitly.  Secondly, that rainfall is strongly affected,
> particularly in the tropics.
>
> "However, the authors chose an extreme climate scenario (4x CO2) so we
> should not be surprised if that, and any geoengineering attempt to counter
> it (also extreme, requiring 100 million tonnes of SO2 per year), had severe
> and uneven impacts.
>
> “I found the press release particularly unhelpful.  Exploratory science
> is rarely as definitive as this.  To state that Solar Radiation Management
> (SRM) won't work based upon one extreme scenario smacks of hype rather than
> a serious discussion.  I know of no serious scientist who would advocate
> introducing 100 megatonnes of sulphur dioxide in a four degree warmer world.
>
> "This new research will doubtless be seized upon by those opposing
> geoengineering research and rebutted by those that support it, in an
> unhelpful, adversarial tit-for-tat.  A more realistic scenario might have
> been to try with 2x CO2 or a specific IPCC projection, and possibly simply
> stabilize (rather than attempt to return to pre-industrial) temperatures.
>  That would probably produce less dire predictions.
>
> "It remains the case that our only guaranteed way forward is to reduce the
> record levels of greenhouse gases we continue to pump 

[geo] Re: runaway climate change

[Govindasamy bala]

Runaway feedback means running its course completely. It is feedback
specific.

A good example is the presumed water vapor feedback on Venus.
Apparently, earth and venus started with similar amount of h2o.
Because Venus started with much higher surface temperature, the evolution of
temperature and water vapor never intercepted the phase line of vapor and
liquid. The climate warmed until all the water got evaporated. Basically,
there was no sink for vapor which precipitation. On earth, this is not going
to happen because we got the precipitation sink on earth...how lucky we are.

But I guess we do have runaway ice-albedo feedback on earth. we could get
ice-free planet or snowball earth

Cheers.
Bala

On Mon, Feb 2, 2009 at 5:03 PM, Eugene I. Gordon wrote:

>
> I guess it is not going to end.
>
> A runaway train meets only #2 and even that has to be qualified because the
> train eventually runs out of (fossil?) fuel or track. Certainly climate has
> run away a half dozen times in 540 million years but always hits a limit
> which seems to be 24C except when an asteroid hits. It eventually turns
> around after remaining at the limit temperature for many millions of years.
> We have been in a runaway mode for the last 18,000 years but with some
> superimposed small wiggles in temperature. Without geoengineering the
> temperature will certainly get to the 24 C limit.
>
> I think runaway is appropriate for the current situation even if there may
> be better suited terms.
>
> -Original Message-
> From: geoengineering@googlegroups.com
> [mailto:geoengineer...@googlegroups.com] On Behalf Of John Nissen
> Sent: Monday, February 02, 2009 6:08 AM
> To: Tom Wigley; Andrew Lockley
> Cc: geoengineering; Prof John Shepherd; Tim Lenton; David Lawrence
> Subject: [geo] Re: runaway climate change
>
>
>
> Dear Tom,
>
> The concept of "runaway" has certain connotations:
>
> 1.  Significant in resultant effect
> 2.  Uncontrollable
> 3.  Exponential initial behaviour - characteristised by acceleration of
> process 4.  No obvious limit 5.  Irreversible 6.  Rapid.
>
> These can all be applied to climate change:
>
> 1.  "Significant" could be over 5 degrees global warming, sufficient for a
> mass extinction event.  Or it could be applied to several metres of sea
> level rise.
> 2.  "Uncontrollable" could be where anthropogenic greenhouse gas emissions
> reduction would not have a significant effect on the rate of climate
> change.
> 3.  Exponential behaviour could be caused by a "tipping" of some part of
> the
> climate system, such as Arctic sea ice or methane release, where there is
> strong positive feedback.
> 4.  There would be no obvious final equilibrium temperature - mainly
> because
> of the difficulty of modelling positive feedback and its behaviour over
> time.
> 5.  It would be extremely difficult or impossible to reverse processes such
> as methane release or Greenland ice sheet disintegration, although it is
> conceivable to halt these processes or even reverse their effects
> (presumably through geoengineering).
> 6.  "Rapid" could be anything from one season to 3000 years, on a
> geological
> timescale.
>
> Therefore I think that "runaway" captures the semantics that we require for
> the climate change that would result from, for example, a massive methane
> release, triggered by Arctic sea ice disappearance.  Can you think of a
> better word to capture the six characteristics above, especially as
> applicable to climate change?
>
> Cheers,
>
> John
>
>
>
> - Original Message -
> From: "Tom Wigley" 
> To: "Andrew Lockley" 
> Cc: ; "geoengineering"
> ; "Prof John Shepherd"
> ; "Tim Lenton" ; "David Lawrence"
> 
> Sent: Monday, February 02, 2009 3:43 AM
> Subject: Re: [geo] Re: runaway climate change
>
>
> > Andrew,
> >
> > Poor analogy. running does not equal running away.
> >
> > More importantly, just because a term has been misused in the
> > past does not mean we should perpetuate its misuse (or use).
> > If the word is to be used at all (and, as a practicing scientist,
> > I never have or will), one should start off by saying that the
> > word runaway is open to misinterpretation, that it does not
> > mean running off to infinity, and that it's real meaning is ...
> > etc. etc. Then talk about irreversible changes (with the caveat
> > that even these are probably not irreversible), positive
> > feedbacks (which also have limits), etc.
> >
> > Tom.
> >
> > +++
> >
> > Andrew Lockley wrote:
> >> For better or worse, the term is now in general use in scientific,
> >> industrial, environmental and general media.  (See
> >> http://en.wikipedia.org/wiki/Runaway_climate_change for refs.)
> >>
> >> I don't agree with Tom about 'to infinity and beyond'.  I run as a
> >> hobby, and I've never run to infinity (or beyond).  I think most
> >> people realise that runaway doesn't mean run-for-ever.
> >>
> >> However, a general definition would be very useful.
> >>
> >> A
> >>
> >>

[geo] Re: runaway climate change

[Govindasamy bala]

Page # 71 of the book "Global warming: Understanding the forecast" by David
Archer has a nice description on runaway feedback.
BTW, I guess there is no such thing as runaway climate change
B

On Mon, Feb 2, 2009 at 5:55 PM, Andrew Lockley wrote:

>
> I have been unable to find any citations in 'hard' climate science
> literature.  Is the term therefore ONLY a pop-science concept?
>
> If anyone has any such citations, please can they send them to me?
>
> A
>
> 2009/2/2 David Schnare :
> > The concept, as applied to climate change, was introduced to discuss loss
> of
> > ice shelves, an "irreversible" event over the short run, and one with
> large
> > consequences.  Then, the concept was expanded to the speed of the event,
> > also as applied to the ice shelves.  Then it was expanded to the "fat
> tail"
> > possibility of very high temperatures.
> >
> > In each case, the presumption (presumption, not reality mind you) was
> that
> > the event was unstoppable once started, much like an explosion.  The
> > inability to "quench" an event should not be confused with the ability to
> > restore (more or less) the initial conditions, or otherwise reach a (new
> or
> > modified) equilibrium.
> >
> > "Runaway" is a loaded term.  We've had a dust up over use of such terms
> in
> > the recent past.  As far as I can tell, at this point, environmental
> > activists are allowed to use them, government employees are not,
> scientists
> > should not, and wiki authors - god knows!
> >
> > Cheers,
> > d.
> >
> > On Mon, Feb 2, 2009 at 6:33 AM, Eugene I. Gordon 
> > wrote:
> >>
> >> I guess it is not going to end.
> >>
> >> A runaway train meets only #2 and even that has to be qualified because
> >> the
> >> train eventually runs out of (fossil?) fuel or track. Certainly climate
> >> has
> >> run away a half dozen times in 540 million years but always hits a limit
> >> which seems to be 24C except when an asteroid hits. It eventually turns
> >> around after remaining at the limit temperature for many millions of
> >> years.
> >> We have been in a runaway mode for the last 18,000 years but with some
> >> superimposed small wiggles in temperature. Without geoengineering the
> >> temperature will certainly get to the 24 C limit.
> >>
> >> I think runaway is appropriate for the current situation even if there
> may
> >> be better suited terms.
> >>
> >> -Original Message-
> >> From: geoengineering@googlegroups.com
> >> [mailto:geoengineer...@googlegroups.com] On Behalf Of John Nissen
> >> Sent: Monday, February 02, 2009 6:08 AM
> >> To: Tom Wigley; Andrew Lockley
> >> Cc: geoengineering; Prof John Shepherd; Tim Lenton; David Lawrence
> >> Subject: [geo] Re: runaway climate change
> >>
> >>
> >>
> >> Dear Tom,
> >>
> >> The concept of "runaway" has certain connotations:
> >>
> >> 1.  Significant in resultant effect
> >> 2.  Uncontrollable
> >> 3.  Exponential initial behaviour - characteristised by acceleration of
> >> process 4.  No obvious limit 5.  Irreversible 6.  Rapid.
> >>
> >> These can all be applied to climate change:
> >>
> >> 1.  "Significant" could be over 5 degrees global warming, sufficient for
> a
> >> mass extinction event.  Or it could be applied to several metres of sea
> >> level rise.
> >> 2.  "Uncontrollable" could be where anthropogenic greenhouse gas
> emissions
> >> reduction would not have a significant effect on the rate of climate
> >> change.
> >> 3.  Exponential behaviour could be caused by a "tipping" of some part of
> >> the
> >> climate system, such as Arctic sea ice or methane release, where there
> is
> >> strong positive feedback.
> >> 4.  There would be no obvious final equilibrium temperature - mainly
> >> because
> >> of the difficulty of modelling positive feedback and its behaviour over
> >> time.
> >> 5.  It would be extremely difficult or impossible to reverse processes
> >> such
> >> as methane release or Greenland ice sheet disintegration, although it is
> >> conceivable to halt these processes or even reverse their effects
> >> (presumably through geoengineering).
> >> 6.  "Rapid" could be anything from one season to 3000 years, on a
> >> geological
> >> timescale.
> >>
> >> Therefore I think that "runaway" captures the semantics that we require
> >> for
> >> the climate change that would result from, for example, a massive
> methane
> >> release, triggered by Arctic sea ice disappearance.  Can you think of a
> >> better word to capture the six characteristics above, especially as
> >> applicable to climate change?
> >>
> >> Cheers,
> >>
> >> John
> >>
> >>
> >>
> >> - Original Message -
> >> From: "Tom Wigley" 
> >> To: "Andrew Lockley" 
> >> Cc: ; "geoengineering"
> >> ; "Prof John Shepherd"
> >> ; "Tim Lenton" ; "David
> Lawrence"
> >> 
> >> Sent: Monday, February 02, 2009 3:43 AM
> >> Subject: Re: [geo] Re: runaway climate change
> >>
> >>
> >> > Andrew,
> >> >
> >> > Poor analogy. running does not equal running away.
> >> >
> >> > More importantly, just because 

[geo] Re: monsoons

[Govindasamy bala]

If I recall going through papers that used IPCC multi-model simulations, the
* mean* Indian Monsoon rainfall is projected to increase between 5 and 25 %
by year 2100. I do not recall the results on intraseasonal and interannual
variability though...

Bala

On Mon, Sep 7, 2009 at 5:17 PM, Peter Read  wrote:

>  Hi John
>
> Thanks for raising this question which puzzles me also
>
> My understanding is that monsoons (Indian, African, South American) depend
> upon a convection cell driven by hot summer air rising over continental
> masses advecting warm wet air from adjacent oceans which gains latent heat
> of condensation from the rains that reinforces the convection cell so that
> there is a bi-stable situation with monsoons if the summer is hot enough
> (reletive to adjacent ocean) and no monsoon if it's not hot enough.
>
> Since the land surface has much lower thermal mass than the (mixed by
> waves) ocean surface, global warming should (I had thought) increase the
> ocean-to-land temperature gradient and strengthen the monsoons.
>
> But this is simple school science reasoning applied at the regional scale
> and maybe more complicated processes are involved in a global model.  But I
> am puzzled by Goswami's result and hope a serious climate scientist can
> provide a simple explanation of the processes involved.
>
> Peter
>
> - Original Message -
> *From:* John Gorman 
> *To:* geoengineering@googlegroups.com
> *Sent:* Monday, September 07, 2009 8:03 PM
> *Subject:* [geo] monsoons
>
>  In  the presentations at the Royal Society on Tuesday 1st September there
> were several suggestions that geoenginering would reduce or stop the Indian
> monsoon.  This was also mentioned in some questions, answers or subsequent
> discussion that I was involved in.
>
>
>
> My suggestion that this would be a result of global warming anyway was
> dismissed by one climate scientist so it was interesting to find the
> following in the Daily Telegraph last Saturday;
>
>
>
> *"Indian Monsoon Could Dry up*
>
> * *
>
> *the torrential rains of India's monsoon could soon be a thing of the past
> after scientist said climate change is replacing the wet season with
> drought.*
>
> * *
>
> *In a study of monsoon patterns in India over the past 150 years BN
> Goswami, the director of the Indian Institute of Tropical Meteorology, said
> global warming has made India's weather increasingly unpredictable.  He
> said there were longer dry spells and shorter sudden heavy showers." *
>
> **
>
> This fits with my general understanding that global warming will produce
> more violent storms but that in India, Africa and Sout America the overall
> result will be rainfall reduction and drought. I have felt that
> geoengineering should be able to reduce storm severity because of less
> extreme temperatures and eventually with experience and planning not impair
> the rainy season in all these places.
>
>
>
> This is in line with a comment of Greg Benfold's some time ago that a
> slight reduction in total rainfall might not matter if we lost the storms
> rather than the background rain.  In India now we seem to be getting the
> opposite.
>
>
>
> Who is right?
>
>
>
> John Gorman
>
>  --
>
>
> No virus found in this incoming message.
> Checked by AVG - www.avg.com
> Version: 8.5.409 / Virus Database: 270.13.81/2350 - Release Date: 09/06/09
> 17:51:00
>
>
> >
>


-- 
Best wishes,

---
Dr. G. Bala
Associate Professor
Center for Atmospheric and Oceanic Sciences
Indian Institute of Science
Bangalore - 560 012
India

Tel: +91 80 2293 2698
   +91 80 2293 2505 x206
   +91 9741991621 (cell)
Fax: +91 80 2360 0865
Email: gb...@caos.iisc.ernet.in
bala@gmail.com
Web:http://caos.iisc.ernet.in/faculty/gbala/gbala.html
---

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[geo] Arctic Geoengineering and Tropical Rainfall

[Govindasamy Bala]

Dear All,


The potential shift in ITCZ due to Arctic geoengineering and the
consequence to rainfall in the global monsoon regions is analyzed in this
Climate Dynamics paper from my research group.


https://link.springer.com/article/10.1007/s00382-017-3810-y

Feel free to download the full text as it is a open access article




*Effects of Arctic geoengineering on precipitation in the tropical monsoon
regionsAditya Nalam · Govindasamy Bala · Angshuman Modak*


*Abstract*

Arctic geoengineering wherein sunlight absorption is reduced only in the
Arctic has been suggested as a remedial measure to counteract the on-going
rapid climate change in the Arctic. Several modeling studies have shown
that Arctic geoengineering can minimize Arctic warming but will shift the
Inter-tropical Convergence Zone (ITCZ) southward, unless offset by
comparable geoengineering in the Southern Hemisphere. In this study, we
investigate and quantify the implications of this ITCZ shift due to Arctic
geoengineering for the global monsoon regions using the Community
Atmosphere Model version 4 coupled to a slab ocean model. A doubling
of CO2 from
pre-industrial levels leads to a warming of ~ 6 K in the Arctic region and
precipitation in the monsoon regions increases by up to ~15 %. In our
Arctic geoengineering simulation which illustrates a plausible latitudinal
distribution of the reduction in sunlight, an addition of sulfate aerosols
(11 Mt) in the Arctic stratosphere nearly offsets the Arctic warming due to
CO2 doubling but this shifts the ITCZ southward by ~1.5⁰ relative to the
pre-industrial climate. The combined effect from this shift and the
residual CO2-induced climate change in the tropics is a decrease/increase
in annual mean precipitation in the Northern Hemisphere /Southern Hemisphere
monsoon regions by up to -12/+17%. Polar geoengineering where sulfate
aerosols are prescribed in both the Arctic (10 Mt) and Antarctic (8 Mt)
nearly offsets the ITCZ shift due to Arctic geoengineering, but there is
still a residual precipitation increase (up to 7 %) in most monsoon regions
associated with  the residual  CO2 induced warming  in the tropics.  The
ITCZ shift due to our Global geoengineering simulation, where aerosols (20
Mt) are prescribed uniformly around the globe, is much smaller and the
precipitation changes in most monsoon regions are within ±2 % as the
residual CO2-induced warming in the tropics is also much less than in
Arctic and Polar geoengineering. Further, global geoengineering nearly
offsets the Arctic warming. Based on our results we infer that Arctic
geoengineering leads to ITCZ shift and leaves residual CO2 induced warming
in the tropics resulting in substantial precipitation decreases (increases)
in the Northern (Southern) hemisphere monsoon regions.


-- 
With Best Wishes,

---
G. Bala
Professor
Center for Atmospheric and Oceanic Sciences
Indian Institute of Science
Bangalore - 560 012
India

Tel: +91 80 2293 3428; +91 80 2293 2505
Fax: +91 80 2360 0865; +91 80 2293 3425
Email: gb...@caos.iisc.ernet.in; bala@gmail.com
Web:http://caos.iisc.ernet.in/faculty/gbala/gbala.html
---

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[geo] Methane Efficacy

[Govindasamy Bala]

Dear All,

Here is the link to our recent paper on the efficacy of Methane in Climate
Dynamics.

https://link.springer.com/article/10.1007/s00382-018-4102-x?wt_mc=Internal.Event.1.SEM.ArticleAuthorOnlineFirst

The efficacy of methane is probably not directly linked to geoengineering
but is an important component of climate change discussions as Methane is
one of the most important short-lived climate forcers.

Does shortwave absorption by methane influence its effectiveness?

   - Angshuman Modak
   
   - Govindasamy Bala
   - Ken Caldeira
   - Long Cao

Abstract

In this study, using idealized step-forcing simulations, we examine the
effective radiative forcing of CH4 relative to that of CO2 and compare the
effects of CH4 and CO2 forcing on the climate system. A tenfold increase in
CH4 concentration in the NCAR CAM5 climate model produces similar long term
global mean surface warming (~ 1.7 K) as a one-third increase in CO2
concentration. However, the radiative forcing estimated for CO2 using the
prescribed-SST method is ~ 81% that of CH4, indicating that the efficacy of
CH4 forcing is ~ 0.81. This estimate is nearly unchanged when the CO2
physiological effect is included in our simulations. Further, for the same
long-term global mean surface warming, we simulate a smaller precipitation
increase in the CH4 case compared to the CO2 case. This is because of the
fast adjustment processes—precipitation reduction in the CH4 case is larger
than that of the CO2 case. This is associated with a relatively more stable
atmosphere and larger atmospheric radiative forcing in the CH4 case which
occurs because of near-infrared absorption by CH4 in the upper troposphere
and lower stratosphere. Within a month after an increase in CH4, this
shortwave heating results in a temperature increase of ~ 0.8 K in the lower
stratosphere and upper troposphere. In contrast, within a month after a CO2
increase, longwave cooling results in a temperature decrease of ~ 3 K in
the stratosphere and a small change in the upper troposphere. These fast
adjustments in the lower stratospheric and upper tropospheric temperature,
along with the adjustments in clouds in the troposphere, influence the
effective radiative forcing and the fast precipitation response. These
differences in fast climate adjustments also produce differences in the
climate states from which the slow response begins to evolve and hence they
are likely associated with differing feedbacks. We also find that the
tropics and subtropics are relatively warmer in the CH4 case for the same
global mean surface warming because of a larger longwave clear-sky and
shortwave cloud forcing over these regions in the CH4 case. Further
investigation using a multi-model intercomparison framework would permit an
assessment of the robustness of our results.
--
With Best Wishes,

---
G. Bala
Professor
Center for Atmospheric and Oceanic Sciences
Indian Institute of Science
Bangalore - 560 012
India

Tel: +91 80 2293 3428; +91 80 2293 2505
Fax: +91 80 2360 0865; +91 80 2293 3425
Email: gb...@caos.iisc.ernet.in; bala@gmail.com
Web:http://caos.iisc.ernet.in/faculty/gbala/gbala.html
---

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[geo] Geoengineering and Precipitation Extremes

[Govindasamy Bala]

Dear All,

This paper (freely downloadable) from my group investigates the effect of
solar geoengineering on precipitation on global and regional scales using
idealized simulations. This is part 1 of a 2-part study.

http://www.currentscience.ac.in/Volumes/114/05/1024.pdf

*Regional scale analysis of climate extremes in *
*an SRM geoengineering simulation, Part 1: precipitation extremes*

Rohi Muthyala1,2, Govindasamy Bala1,* and Aditya Nalam1
1Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science,
Bengaluru 560 012, India
2Present address: Department of Geography, Rutgers, The State University of
New Jersey, Piscataway, NJ 08854, USA


Abstract

In this study, we examine the statistics of precipitation
extreme events in a model simulation of solar radiation
management (SRM) geoengineering. We consider
both intensity and frequency-based extreme indices for
precipitation. The analysis is performed over both
large-scale domains as well as regional scales (22 Giorgi
land regions). We find that precipitation extremes are
substantially reduced in geoengineering simulation: the
magnitude of change is much smaller than those that
occur in a simulation with elevated atmospheric CO2
alone. In the geoengineered climate, though the global
mean of the intensity of extreme precipitation events is
slightly less than in control climate, substantial changes
remain on regional scales. We do not find significant
changes in the frequency of precipitation extremes in
geoengineering simulation compared to control simulation on global and
regional scales. We infer that SRM schemes are likely to reduce
precipitation extremes and the associated impacts on a global scale.
However, we note that a comprehensive assessment of moral, social, ethical,
legal, technological, economic, political and governance issues is required
for using SRM methods to counter the impacts of climate change.


-- 
With Best Wishes,

---
G. Bala
Professor
Center for Atmospheric and Oceanic Sciences
Indian Institute of Science
Bangalore - 560 012
India

Tel: +91 80 2293 3428; +91 80 2293 2505
Fax: +91 80 2360 0865; +91 80 2293 3425
Email: gb...@caos.iisc.ernet.in; bala@gmail.com
Web:http://caos.iisc.ernet.in/faculty/gbala/gbala.html
---

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[geo] Geoengineering and temperature extremes

[Govindasamy Bala]

Dear all,

This paper (freely downloadable) from my group investigates the effect of
solar geoengineering on temperature extremes on global and regional scales
using idealized simulations. This is part 2 of the 2-part study.

http://www.currentscience.ac.in/Volumes/114/05/1036.pdf





*Regional scale analysis of climate extremes inan SRM geoengineering
simulation, Part 2:temperature extremes*Rohi Muthyala1,2, Govindasamy
Bala1,* and Aditya Nalam1
1Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science,
Bengaluru 560 012, India
2Present address: Department of Geography, Rutgers, The State University of
New Jersey, Piscataway, NJ 08854, USA


In this study, we examine the statistics of temperature
extremes in a model simulation of solar radiation
management (SRM) geoengineering. We consider both
intensity and frequency-based extreme indices for
temperature. The analysis is performed over both
large-scale domains as well as regional scales (22
Giorgi land regions). We find that temperature
extremes are substantially reduced in geoengineering
simulation: the magnitude of change is much smaller
than that occur in a simulation with elevated atmospheric
CO2 alone. Large increase (~10–20 K) in the
lower tails (0.1 percentile) of Tmin and Tmax in the
northern hemisphere extra-tropics that are simulated
under doubling of CO2 are reduced in geoengineering
simulation, but significant increase (~4–7 K) persist
over high-latitude land regions. Frequency of temperature
extremes is largely offset over land regions in
geoengineered climate. We infer that SRM schemes
are likely to reduce temperature extremes and the
associated impacts on a global scale. However, we note
that a comprehensive assessment of moral, social,
ethical, legal, technological, economic, political and
governance issues is required for using SRM methods
to counter the impacts of climate change.


-- 
With Best Wishes,

---
G. Bala
Professor
Center for Atmospheric and Oceanic Sciences
Indian Institute of Science
Bangalore - 560 012
India

Tel: +91 80 2293 3428; +91 80 2293 2505
Fax: +91 80 2360 0865; +91 80 2293 3425
Email: gb...@caos.iisc.ernet.in; bala@gmail.com
Web:http://caos.iisc.ernet.in/faculty/gbala/gbala.html
---

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[geo] Nature Letter - India forges ahead with solar-geoengineering studies

[Govindasamy Bala]

Dear All,

This brief correspondence appears in this weeks Nature Correspondence:

India forges ahead with solar-geoengineering studies
Govindasamy Bala and Akhilesh Gupta


India has been contributing to the evaluation, discussion and
implementation of solar-geoengineering research for almost a decade, in
line with the call by A. Atiq Rahman and colleagues for developing
countries to take the lead in this realm (see *Nature* 556, 22–24; 2018
<https://www.nature.com/articles/d41586-018-03917-8>).

The Indian government’s Department of Science and Technology launched a
major research initiative in 2017 at the Indian Institute of Science in
Bangalore to understand the implications of solar geoengineering on
developing countries. The first annual meeting of experts and policymakers
to discuss how this research could be done in India was held in 2017.

The department has also funded a geoengineering climate-modelling research
programme over the past five years. This has revealed, for example, how
solar geoengineering could affect the global water cycle and extreme events
and cyclones in the Bay of Bengal (see G. Bala and B. Nag *Clim. Dyn.* *39*,
1527–1542; 2012 <https://doi.org/10.1007/s00382-011-1256-1>; and A. Nalam *et
al. Clim. Dyn. **50*, 3375–3395; 2018
<https://doi.org/10.1007/s00382-017-3810-y>).

Furthermore, New Delhi’s Council on Energy, Environment and Water has held
three international conferences since 2011 to identify India’s role in
developing regional and global governance of solar-geoengineering research
and technologies.

Nature *557*, 637 (2018)
doi: 10.1038/d41586-018-05288-6




-- 
With Best Wishes,

---
G. Bala
Professor
Center for Atmospheric and Oceanic Sciences
Indian Institute of Science
Bangalore - 560 012
India

Tel: +91 80 2293 3428; +91 80 2293 2505
Fax: +91 80 2360 0865; +91 80 2293 3425
Email: gb...@caos.iisc.ernet.in; bala@gmail.com
Web:http://caos.iisc.ernet.in/faculty/gbala/gbala.html
---

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[geo] Geoengineering: Should India Tread Carefully or Go Full Steam Ahead?

[Govindasamy Bala]

https://thewire.in/the-sciences/geoengineering-should-india-tread-carefully-or-go-full-steam-ahead

Geoengineering: Should India Tread Carefully or Go Full Steam Ahead?

Solar geoengineering doesn’t help reduce carbon emissions, and is founded
on reckoning with the distressing possibility that reduction strategies
won’t be enough.

-- 
With Best Wishes,

---
G. Bala
Professor
Center for Atmospheric and Oceanic Sciences
Indian Institute of Science
Bangalore - 560 012
India

Tel: +91 80 2293 3428; +91 80 2293 2505
Fax: +91 80 2360 0865; +91 80 2293 3425
Email: gb...@caos.iisc.ernet.in; bala@gmail.com
Web:http://caos.iisc.ernet.in/faculty/gbala/gbala.html
---

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[geo] Sensitivity of the surface climate to the height of the stratospheric sulfate layer

[Govindasamy Bala]

Dear All,

This work is now published in Earth System Dynamics as a discussion paper.
When we started this work, we had hard time understanding the sensitivity
to the height of the sulfate aerosol layer. In the paper, we explain the
sensitivity in terms of the effective radiative forcing.


https://www.earth-syst-dynam-discuss.net/esd-2019-21/
ESDD - Climate System Response to Stratospheric Sulfate Aerosols:
Sensitivity to Altitude of Aerosol Layer - earth-syst-dynam-discuss.net

www.earth-syst-dynam-discuss.net
We find that sulfate aerosols are more effective in cooling the climate
system when they reside higher in the stratosphere. We explain this
sensitivity in terms of radiative forcing at the top of the atmosphere.

*Abstract*
Reduction of surface temperatures of the planet by injecting sulfate
aerosols in the stratosphere has been suggested
as an option to reduce the amount of human-induced climate warming. Several
previous studies have shown that for a specified amount of injection,
aerosols injected at a higher altitude in the stratosphere would produce
more cooling because aerosol sedimentation would take longer time. In this
study, we isolate and assess the sensitivity to the altitude of the aerosol
layer of stratospheric aerosol radiative forcing and the resulting climate
change. We study this by prescribing a specified amount of sulfate
aerosols, of a size typical of what is produced by volcanoes, distributed
uniformly at different levels in the stratosphere. We find that
stratospheric sulfate aerosols are more effective in cooling climate when
they reside higher in the stratosphere. We explain this sensitivity in
terms of effective radiative forcing: volcanic aerosols heat the
stratospheric layers where they reside, altering stratospheric water vapor
content, tropospheric stability and clouds, and consequently the effective
radiative forcing. We show that the magnitude of the effective radiative
forcing is larger when aerosols are prescribed at higher altitudes and the
differences in radiative forcing due to fast adjustment processes can
account for a substantial part of the dependence of amount of cooling on
aerosol altitude. These altitude effects would be additional to dependences
on aerosol microphysics, transport, and sedimentation, which are outside
the scope of this study. The cooling effectiveness of stratospheric sulfate
aerosols likely increases with altitude of the aerosol layer both because
aerosols higher in the stratosphere have larger effective radiative forcing
and because they have a longer stratospheric residence time; these two
effects are likely to be of comparable importance.
-- 
With Best Wishes,

---
G. Bala
Professor
Center for Atmospheric and Oceanic Sciences
Indian Institute of Science
Bangalore - 560 012
India

Tel: +91 80 2293 3428; +91 80 2293 2505
Fax: +91 80 2360 0865; +91 80 2293 3425
Email: gb...@iisc.ac.in; bala@gmail.com
Web:  http://dccc.iisc.ac.in/bg.html
---

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Re: [geo] Climate system response to stratospheric sulfate aerosols: sensitivity to altitude of aerosol layer

[Govindasamy Bala]

Dear Andrew,
Thanks for the posting. The heights studied were 16, 19 and 22 km, height
that are relevant to solar radiation modification problem.. The final
paragraph in the paper is worth reading to get more quantitative
information from this modeling study.

"To summarize, for the same mass, the efficiency (defined
as changes in surface temperature per Tg S) of volcanic
aerosol is less when it is prescribed at lower altitudes in the
stratosphere (Fig. 9). For example, in our simulations, there is
a surface cooling of 0.44K for each teragram of sulfur placed
in the stratosphere at about 16 km altitude (100 hPa). There
is an additional surface cooling of 0.15K per Tg S when the
prescribed altitude is increased from about 16 km to about
22 km (37 hPa)."

On Sat, Dec 14, 2019 at 12:55 AM Andrew Lockley 
wrote:

> Poster's note : this has significant implications for the engineering of
> delivery systems. I can't do the pressure altitude conversion in my head,
> but it's a lot higher than what's generally been planned for. We're gonna
> need a bigger boat.
>
>
> https://www.earth-syst-dynam.net/10/885/2019/
>
> Climate system response to stratospheric sulfate aerosols: sensitivity to
> altitude of aerosol layer
> Krishna-Pillai Sukumara-Pillai Krishnamohan et al. Received: 01 May
> 2019 – Discussion started: 23 May 2019 – Revised: 24 Oct 2019 – Accepted:
> 08 Nov 2019 – Published: 13 Dec 2019
> Abstract
> top 
>
> Reduction of surface temperatures of the planet by injecting sulfate
> aerosols in the stratosphere has been suggested as an option to reduce the
> amount of human-induced climate warming. Several previous studies have
> shown that for a specified amount of injection, aerosols injected at a
> higher altitude in the stratosphere would produce more cooling because
> aerosol sedimentation would take longer. In this study, we isolate and
> assess the sensitivity of stratospheric aerosol radiative forcing and the
> resulting climate change to the altitude of the aerosol layer. We study
> this by prescribing a specified amount of sulfate aerosols, of a size
> typical of what is produced by volcanoes, distributed uniformly at
> different levels in the stratosphere. We find that stratospheric sulfate
> aerosols are more effective in cooling climate when they reside higher in
> the stratosphere. We explain this sensitivity in terms of effective
> radiative forcing: volcanic aerosols heat the stratospheric layers where
> they reside, altering stratospheric water vapor content, tropospheric
> stability, and clouds, and consequently the effective radiative forcing. We
> show that the magnitude of the effective radiative forcing is larger when
> aerosols are prescribed at higher altitudes and the differences in
> radiative forcing due to fast adjustment processes can account for a
> substantial part of the dependence of the amount of cooling on aerosol
> altitude. These altitude effects would be additional to dependences on
> aerosol microphysics, transport, and sedimentation, which are outside the
> scope of this study. The cooling effectiveness of stratospheric sulfate
> aerosols likely increases with the altitude of the aerosol layer both
> because aerosols higher in the stratosphere have larger effective radiative
> forcing and because they have higher stratospheric residence time; these
> two effects are likely to be of comparable importance.
>
> --
> You received this message because you are subscribed to the Google Groups
> "geoengineering" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to geoengineering+unsubscr...@googlegroups.com.
> To view this discussion on the web visit
> https://groups.google.com/d/msgid/geoengineering/CAJ3C-04wbNfg0E3q_8GtwXay88n_2r%2BhzYfVfrNPjq9SpJd9pg%40mail.gmail.com
> 
> .
>


-- 
With Best Wishes,

---
G. Bala
Professor
Center for Atmospheric and Oceanic Sciences
Indian Institute of Science
Bangalore - 560 012
India

Tel: +91 80 2293 3428; +91 80 2293 2505
Fax: +91 80 2360 0865; +91 80 2293 3425
Email: gb...@iisc.ac.in; bala@gmail.com
Web:http://dccc.iisc.ac.in/dr_govindasamy_bala_profile.html
---

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Re: [geo] Climate system response to stratospheric sulfate aerosols: sensitivity to altitude of aerosol layer

[Govindasamy Bala]

Andrews,

We did not do experiments with aerosols above 22 km. It is likely that the
cooling effect will be larger when aerosols are at 25 km. Beyond that it is
likely that the additional cooling benefits disappear. We need more
experiments to confirm this.

The sensitivity to height in our paper arises mainly because of the
increases in stratospheric water vapor (which partly offsets the cooling
efficiency of the aerosols) that is associated with the stratospheric
heating by the aerosols. This increase in stratospheric water vapor is
largest when the aerosols (and the heating) is close to the tropopause.

In our paper, we have isolated the effect of just one factor. As Doug has
pointed out, the sedimentation effect would also lead to more cooling if
aerosols are injected at higher altitudes...

Best,
Bala

On Sun, Dec 15, 2019 at 9:05 PM Douglas MacMartin 
wrote:

> This is a great study to understand the effectiveness per unit mass **in
> the stratosphere**.  Also keep in mind that there’s an additional factor,
> that at lower altitudes it takes higher injection rates to achieve the same
> burden in the stratosphere (i.e., lower lifetime at lower injected
> altitude).
>
>
>
> If the only thing you cared about was cost, then since there are existing
> studies demonstrating that you can design an aircraft to get to ~20-21km,
> we roughly know that it could be done, but higher altitude injection means
> less total sulfur injected and hence smaller side effects, and should be
> better understood both on the modeling and implementation cost as the trade
> may well be worth it.
>
>
>
> doug
>
>
>
> *From:* geoengineering@googlegroups.com  *On
> Behalf Of *Govindasamy Bala
> *Sent:* Saturday, December 14, 2019 9:38 PM
> *To:* Andrew Lockley 
> *Cc:* geoengineering 
> *Subject:* Re: [geo] Climate system response to stratospheric sulfate
> aerosols: sensitivity to altitude of aerosol layer
>
>
>
> Dear Andrew,
>
> Thanks for the posting. The heights studied were 16, 19 and 22 km, height
> that are relevant to solar radiation modification problem.. The final
> paragraph in the paper is worth reading to get more quantitative
> information from this modeling study.
>
>
>
> "To summarize, for the same mass, the efficiency (defined
>
> as changes in surface temperature per Tg S) of volcanic
> aerosol is less when it is prescribed at lower altitudes in the
> stratosphere (Fig. 9). For example, in our simulations, there is
> a surface cooling of 0.44K for each teragram of sulfur placed
> in the stratosphere at about 16 km altitude (100 hPa). There
> is an additional surface cooling of 0.15K per Tg S when the
> prescribed altitude is increased from about 16 km to about
> 22 km (37 hPa)."
>
>
>
> On Sat, Dec 14, 2019 at 12:55 AM Andrew Lockley 
> wrote:
>
> Poster's note : this has significant implications for the engineering of
> delivery systems. I can't do the pressure altitude conversion in my head,
> but it's a lot higher than what's generally been planned for. We're gonna
> need a bigger boat.
>
>
>
>
>
> https://www.earth-syst-dynam.net/10/885/2019/
>
>
>
> Climate system response to stratospheric sulfate aerosols: sensitivity to
> altitude of aerosol layer
>
> *Krishna-Pillai Sukumara-Pillai Krishnamohan et al. *Received: 01 May
> 2019 – Discussion started: 23 May 2019 – Revised: 24 Oct 2019 – Accepted:
> 08 Nov 2019 – Published: 13 Dec 2019
>
> Abstract
>
> top <https://www.earth-syst-dynam.net/10/885/2019/#top>
>
> Reduction of surface temperatures of the planet by injecting sulfate
> aerosols in the stratosphere has been suggested as an option to reduce the
> amount of human-induced climate warming. Several previous studies have
> shown that for a specified amount of injection, aerosols injected at a
> higher altitude in the stratosphere would produce more cooling because
> aerosol sedimentation would take longer. In this study, we isolate and
> assess the sensitivity of stratospheric aerosol radiative forcing and the
> resulting climate change to the altitude of the aerosol layer. We study
> this by prescribing a specified amount of sulfate aerosols, of a size
> typical of what is produced by volcanoes, distributed uniformly at
> different levels in the stratosphere. We find that stratospheric sulfate
> aerosols are more effective in cooling climate when they reside higher in
> the stratosphere. We explain this sensitivity in terms of effective
> radiative forcing: volcanic aerosols heat the stratospheric layers where
> they reside, altering stratospheric water vapor content, tropospheric
> stability, and clouds, and consequently the effective radiative forcing. We
> show that th

Re: [geo] Climate system response to stratospheric sulfate aerosols: sensitivity to altitude of aerosol layer

[Govindasamy Bala]

Andrew,
Many modeling groups (e.g. Tilmes and others) have already performed
simulations that inject aerosols at different heights and thus have
included the sedimentation effects and many many other effects. These
studies simulate the NET effects and hence hard to interpret and quantify
the individual effects. The strength of our ESD paper is that it changes
only one variable and identifies its individual contribution to the total
problem.

What we have learnt during the course is that there are too many variables
in the aerosol SRM problem (transport, location of injection, aerosol-cloud
interaction, aerosol-radiation interaction, aerosol micro physics and the
resulting size distribution of the aerosols, etc.) and the resulting
uncertainties could be too large. This is of course known to many of us for
a long time..

On Mon, Dec 16, 2019 at 3:41 PM Andrew Lockley 
wrote:

> If I understand from the email below , you used aerosols with no fall
> speed. Are experiments planned to simulate aerosol descent?
>
> Andrew
>
> On Mon, 16 Dec 2019, 05:43 Govindasamy Bala,  wrote:
>
>> Andrews,
>>
>> We did not do experiments with aerosols above 22 km. It is likely that
>> the cooling effect will be larger when aerosols are at 25 km. Beyond that
>> it is likely that the additional cooling benefits disappear. We need more
>> experiments to confirm this.
>>
>> The sensitivity to height in our paper arises mainly because of the
>> increases in stratospheric water vapor (which partly offsets the cooling
>> efficiency of the aerosols) that is associated with the stratospheric
>> heating by the aerosols. This increase in stratospheric water vapor is
>> largest when the aerosols (and the heating) is close to the tropopause.
>>
>> In our paper, we have isolated the effect of just one factor. As Doug has
>> pointed out, the sedimentation effect would also lead to more cooling if
>> aerosols are injected at higher altitudes...
>>
>> Best,
>> Bala
>>
>> On Sun, Dec 15, 2019 at 9:05 PM Douglas MacMartin 
>> wrote:
>>
>>> This is a great study to understand the effectiveness per unit mass **in
>>> the stratosphere**.  Also keep in mind that there’s an additional
>>> factor, that at lower altitudes it takes higher injection rates to achieve
>>> the same burden in the stratosphere (i.e., lower lifetime at lower injected
>>> altitude).
>>>
>>>
>>>
>>> If the only thing you cared about was cost, then since there are
>>> existing studies demonstrating that you can design an aircraft to get to
>>> ~20-21km, we roughly know that it could be done, but higher altitude
>>> injection means less total sulfur injected and hence smaller side effects,
>>> and should be better understood both on the modeling and implementation
>>> cost as the trade may well be worth it.
>>>
>>>
>>>
>>> doug
>>>
>>>
>>>
>>> *From:* geoengineering@googlegroups.com 
>>> *On Behalf Of *Govindasamy Bala
>>> *Sent:* Saturday, December 14, 2019 9:38 PM
>>> *To:* Andrew Lockley 
>>> *Cc:* geoengineering 
>>> *Subject:* Re: [geo] Climate system response to stratospheric sulfate
>>> aerosols: sensitivity to altitude of aerosol layer
>>>
>>>
>>>
>>> Dear Andrew,
>>>
>>> Thanks for the posting. The heights studied were 16, 19 and 22 km,
>>> height that are relevant to solar radiation modification problem.. The
>>> final paragraph in the paper is worth reading to get more quantitative
>>> information from this modeling study.
>>>
>>>
>>>
>>> "To summarize, for the same mass, the efficiency (defined
>>>
>>> as changes in surface temperature per Tg S) of volcanic
>>> aerosol is less when it is prescribed at lower altitudes in the
>>> stratosphere (Fig. 9). For example, in our simulations, there is
>>> a surface cooling of 0.44K for each teragram of sulfur placed
>>> in the stratosphere at about 16 km altitude (100 hPa). There
>>> is an additional surface cooling of 0.15K per Tg S when the
>>> prescribed altitude is increased from about 16 km to about
>>> 22 km (37 hPa)."
>>>
>>>
>>>
>>> On Sat, Dec 14, 2019 at 12:55 AM Andrew Lockley <
>>> andrew.lock...@gmail.com> wrote:
>>>
>>> Poster's note : this has significant implications for the engineering of
>>> delivery systems. I can't do the pressure altitude conversion in my head,
>>> but it's a lot higher than w

Re: [geo] Climate system response to stratospheric sulfate aerosols: sensitivity to altitude of aerosol layer

[Govindasamy Bala]

Andrew,

Sedimentation effect works in the same direction as the effect we
identified in our study. Therefore, higher the altitude of injection, the
better. My judgement: 25 km would be good.

On Mon, Dec 16, 2019 at 8:54 PM Andrew Lockley 
wrote:

> So what's your judgement on the ideal injection altitude?
>
> Andrew
>
> On Mon, 16 Dec 2019, 10:36 Govindasamy Bala,  wrote:
>
>> Andrew,
>> Many modeling groups (e.g. Tilmes and others) have already performed
>> simulations that inject aerosols at different heights and thus have
>> included the sedimentation effects and many many other effects. These
>> studies simulate the NET effects and hence hard to interpret and quantify
>> the individual effects. The strength of our ESD paper is that it changes
>> only one variable and identifies its individual contribution to the total
>> problem.
>>
>> What we have learnt during the course is that there are too many
>> variables in the aerosol SRM problem (transport, location of injection,
>> aerosol-cloud interaction, aerosol-radiation interaction, aerosol micro
>> physics and the resulting size distribution of the aerosols, etc.) and the
>> resulting uncertainties could be too large. This is of course known to many
>> of us for a long time..
>>
>> On Mon, Dec 16, 2019 at 3:41 PM Andrew Lockley 
>> wrote:
>>
>>> If I understand from the email below , you used aerosols with no fall
>>> speed. Are experiments planned to simulate aerosol descent?
>>>
>>> Andrew
>>>
>>> On Mon, 16 Dec 2019, 05:43 Govindasamy Bala,  wrote:
>>>
>>>> Andrews,
>>>>
>>>> We did not do experiments with aerosols above 22 km. It is likely that
>>>> the cooling effect will be larger when aerosols are at 25 km. Beyond that
>>>> it is likely that the additional cooling benefits disappear. We need more
>>>> experiments to confirm this.
>>>>
>>>> The sensitivity to height in our paper arises mainly because of the
>>>> increases in stratospheric water vapor (which partly offsets the cooling
>>>> efficiency of the aerosols) that is associated with the stratospheric
>>>> heating by the aerosols. This increase in stratospheric water vapor is
>>>> largest when the aerosols (and the heating) is close to the tropopause.
>>>>
>>>> In our paper, we have isolated the effect of just one factor. As Doug
>>>> has pointed out, the sedimentation effect would also lead to more cooling
>>>> if aerosols are injected at higher altitudes...
>>>>
>>>> Best,
>>>> Bala
>>>>
>>>> On Sun, Dec 15, 2019 at 9:05 PM Douglas MacMartin 
>>>> wrote:
>>>>
>>>>> This is a great study to understand the effectiveness per unit mass **in
>>>>> the stratosphere**.  Also keep in mind that there’s an additional
>>>>> factor, that at lower altitudes it takes higher injection rates to achieve
>>>>> the same burden in the stratosphere (i.e., lower lifetime at lower 
>>>>> injected
>>>>> altitude).
>>>>>
>>>>>
>>>>>
>>>>> If the only thing you cared about was cost, then since there are
>>>>> existing studies demonstrating that you can design an aircraft to get to
>>>>> ~20-21km, we roughly know that it could be done, but higher altitude
>>>>> injection means less total sulfur injected and hence smaller side effects,
>>>>> and should be better understood both on the modeling and implementation
>>>>> cost as the trade may well be worth it.
>>>>>
>>>>>
>>>>>
>>>>> doug
>>>>>
>>>>>
>>>>>
>>>>> *From:* geoengineering@googlegroups.com <
>>>>> geoengineering@googlegroups.com> *On Behalf Of *Govindasamy Bala
>>>>> *Sent:* Saturday, December 14, 2019 9:38 PM
>>>>> *To:* Andrew Lockley 
>>>>> *Cc:* geoengineering 
>>>>> *Subject:* Re: [geo] Climate system response to stratospheric sulfate
>>>>> aerosols: sensitivity to altitude of aerosol layer
>>>>>
>>>>>
>>>>>
>>>>> Dear Andrew,
>>>>>
>>>>> Thanks for the posting. The heights studied were 16, 19 and 22 km,
>>>>> height that are relevant to solar radiation modification problem.. The
>>>>> final paragraph in the paper is worth re

Re: [geo] Climate system response to stratospheric sulfate aerosols: sensitivity to altitude of aerosol layer

[Govindasamy Bala]

26 km is probably not going to add any more benefit compared 25 km if you
consider the effect identified in our paper but it is better when
sedimentation effect is considered. More experiments with the NCAR WACCM
model would be good to precisely nail this down.

On Tue, Dec 17, 2019 at 2:10 PM Andrew Lockley 
wrote:

> Is 26k less good than 25?
>
> On Tue, 17 Dec 2019, 08:37 Govindasamy Bala,  wrote:
>
>> Andrew,
>>
>> Sedimentation effect works in the same direction as the effect we
>> identified in our study. Therefore, higher the altitude of injection, the
>> better. My judgement: 25 km would be good.
>>
>> On Mon, Dec 16, 2019 at 8:54 PM Andrew Lockley 
>> wrote:
>>
>>> So what's your judgement on the ideal injection altitude?
>>>
>>> Andrew
>>>
>>> On Mon, 16 Dec 2019, 10:36 Govindasamy Bala,  wrote:
>>>
>>>> Andrew,
>>>> Many modeling groups (e.g. Tilmes and others) have already performed
>>>> simulations that inject aerosols at different heights and thus have
>>>> included the sedimentation effects and many many other effects. These
>>>> studies simulate the NET effects and hence hard to interpret and quantify
>>>> the individual effects. The strength of our ESD paper is that it changes
>>>> only one variable and identifies its individual contribution to the total
>>>> problem.
>>>>
>>>> What we have learnt during the course is that there are too many
>>>> variables in the aerosol SRM problem (transport, location of injection,
>>>> aerosol-cloud interaction, aerosol-radiation interaction, aerosol micro
>>>> physics and the resulting size distribution of the aerosols, etc.) and the
>>>> resulting uncertainties could be too large. This is of course known to many
>>>> of us for a long time..
>>>>
>>>> On Mon, Dec 16, 2019 at 3:41 PM Andrew Lockley <
>>>> andrew.lock...@gmail.com> wrote:
>>>>
>>>>> If I understand from the email below , you used aerosols with no fall
>>>>> speed. Are experiments planned to simulate aerosol descent?
>>>>>
>>>>> Andrew
>>>>>
>>>>> On Mon, 16 Dec 2019, 05:43 Govindasamy Bala, 
>>>>> wrote:
>>>>>
>>>>>> Andrews,
>>>>>>
>>>>>> We did not do experiments with aerosols above 22 km. It is likely
>>>>>> that the cooling effect will be larger when aerosols are at 25 km. Beyond
>>>>>> that it is likely that the additional cooling benefits disappear. We need
>>>>>> more experiments to confirm this.
>>>>>>
>>>>>> The sensitivity to height in our paper arises mainly because of the
>>>>>> increases in stratospheric water vapor (which partly offsets the cooling
>>>>>> efficiency of the aerosols) that is associated with the stratospheric
>>>>>> heating by the aerosols. This increase in stratospheric water vapor is
>>>>>> largest when the aerosols (and the heating) is close to the tropopause.
>>>>>>
>>>>>> In our paper, we have isolated the effect of just one factor. As Doug
>>>>>> has pointed out, the sedimentation effect would also lead to more cooling
>>>>>> if aerosols are injected at higher altitudes...
>>>>>>
>>>>>> Best,
>>>>>> Bala
>>>>>>
>>>>>> On Sun, Dec 15, 2019 at 9:05 PM Douglas MacMartin 
>>>>>> wrote:
>>>>>>
>>>>>>> This is a great study to understand the effectiveness per unit mass **in
>>>>>>> the stratosphere**.  Also keep in mind that there’s an additional
>>>>>>> factor, that at lower altitudes it takes higher injection rates to 
>>>>>>> achieve
>>>>>>> the same burden in the stratosphere (i.e., lower lifetime at lower 
>>>>>>> injected
>>>>>>> altitude).
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> If the only thing you cared about was cost, then since there are
>>>>>>> existing studies demonstrating that you can design an aircraft to get to
>>>>>>> ~20-21km, we roughly know that it could be done, but higher altitude
>>>>>>> injection means less total sulfur injected and hence smaller side 
>>>>>

[geo] [paper] The Climatic Effects of Hygroscopic Growth of Sulfate Aerosols in the Stratosphere

[Govindasamy Bala]

Hi Andrews,

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019EF001326

This paper in Earth's Future (published online last week) quantifies the
climatic effects of hygroscopic growth of sulfate aerosols in the
stratosphere. Here, the cooling effect is more when aerosols are placed in
the lower stratosphere. This is exactly opposite to the sedimentation
related residence time effects and the effects associated with the
stratospheric heating induced by aerosols (our recent study published in
Earth System Dynamics, both abstracts are shown below). Looks like too many
factors are involved in deciding the net effect.

The Climatic Effects of Hygroscopic Growth of Sulfate Aerosols in the
Stratosphere


Abstract

Solar geoengineering by deliberate injection of sulfate aerosols in the
stratosphere is one of the proposed options to counter anthropogenic
climate warming. In this study, we focus on the effect of a specific
microphysical property of sulfate aerosols in the stratosphere: hygroscopic
growth ‐ the tendency of particles to grow by accumulating water. We show
that stratospheric sulfate aerosols, for a given mass of sulfates, cause
more cooling when prescribed at the lower levels of the stratosphere
because of hygroscopic growth. The larger relative humidity in the lower
stratosphere causes an increase in the aerosol size through hygroscopic
growth which leads to a larger scattering efficiency. In our study,
hygroscopic growth provides an additional cooling of 23% (0.7 K) when 20
Mt‐SO4 of sulfate aerosols, an amount that approximately offsets the
warming due to a doubling of CO2, are prescribed at 100 hPa. The
hygroscopic effect becomes weaker at higher levels as relative humidity
decreases with height. Hygroscopic growth also leads to secondary effects
such as an increase in near‐IR shortwave absorption by the aerosols which
causes a decrease in high clouds and an increase in stratospheric water
vapor. The altitude dependence of the effects of hygroscopic growth is
opposite to that of sedimentation effects or the fast adjustment effects
due to aerosol‐induced warming identified in a recent study.

https://www.earth-syst-dynam.net/10/885/2019/

*Climate system response to stratospheric sulfate*
*aerosols: sensitivity to altitude of aerosol layer*

Abstract. Reduction of surface temperatures of the planet by injecting
sulfate aerosols in the stratosphere has been suggested as an option to
reduce the amount of human-induced climate warming. Several previous studies
have shown that for a specified amount of injection, aerosols injected at a
higher altitude in the stratosphere would produce more cooling because
aerosol sedimentation would take longer. In this study, we isolate and
assess the
sensitivity of stratospheric aerosol radiative forcing and the resulting
climate change to the altitude of the aerosol layer.We study this by
prescribing a specified amount of sulfate aerosols, of a size typical of
what is produced by
volcanoes, distributed uniformly at different levels in the stratosphere.We
find that stratospheric sulfate aerosols are more effective in cooling
climate when they reside higher in the stratosphere. We explain this
sensitivity in
terms of effective radiative forcing: volcanic aerosols heat the
stratospheric layers where they reside, altering stratospheric water vapor
content, tropospheric stability, and clouds, and consequently the effective
radiative
forcing. We show that the magnitude of the effective radiative forcing is
larger when aerosols are prescribed at higher altitudes and the differences
in radiative forcing due to fast adjustment processes can account for a
substantial part of the dependence of the amount of cooling on aerosol
altitude. These altitude effects would be additional to dependences on
aerosol microphysics, transport, and sedimentation, which are outside the
scope of this study. The cooling effectiveness of stratospheric sulfate
aerosols likely increases with the altitude of the aerosol layer both
because aerosols higher in the stratosphere have larger effective radiative
forcing and because they have higher stratospheric residence time; these
two effects are likely to be of comparable importance.

-- 
With Best Wishes,

---
G. Bala
Professor
Center for Atmospheric and Oceanic Sciences
Indian Institute of Science
Bangalore - 560 012
India

Tel: +91 80 2293 3428; +91 80 2293 2505
Fax: +91 80 2360 0865; +91 80 2293 3425
Email: gb...@iisc.ac.in; bala@gmail.com
---

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Re: [geo] IPCC Review Comments - AR6WG1 - SOD

[Govindasamy Bala]

SRM is assessed in section 4.6.3.3

CDR is assessed in section 5.6

On Mon, Mar 16, 2020 at 6:31 PM Andrew Lockley 
wrote:

> Poster's note: IDK whether this has any SRM/CDR relevant chapters, but I'm
> sure many people on these lists will want to sign up, anyway. Feedback on
> likely contents would be useful.
>
> https://apps.ipcc.ch/comments/ar6wg1/sod/register.php
>
> Working Group I contribution to the IPCC Sixth Assessment Report -
> RegistrationSecond Order Draft Expert Review
>
> The Expert Review of the Second Order Draft Draft of the Working Group I
> Contribution to the IPCC Sixth Assessment Report will run from 02 Mar 2020
> to 26 Apr 2020. Registration will be open until *2020-04-19 23:59 (CST)*.
> Chapters you are interested in reviewing
> ATLAS
> Chapter 1: Framing, context, methods
> Chapter 2: Changing state of the climate system
> Chapter 3: Human influence on the climate system
> Chapter 4: Future global climate: scenario-based projections and near-term
> information
> Chapter 5: Global carbon and other biogeochemical cycles and feedbacks
> Chapter 6: Short-lived climate forcers
> Chapter 7: The Earth's energy budget, climate feedbacks, and climate
> sensitivity
> Chapter 8: Water cycle changes
> Chapter 9: Ocean, cryosphere, and sea level change
> Chapter 10: Linking global to regional climate change
> Chapter 11: Weather and climate extreme events in a changing climate
> Chapter 12: Climate change information for regional impact and for risk
> assessment
> Technical Summary
> Glossary
> FAQ
> Annex I - Observations
> Annex II - Paleo
> Annex III - Models
> Summary For Policymakers
> Annex V - Radiative forcing
> Annex VI - Modes of variability
> Annex VII - Hazard and Extreme Indices
> Entire Report
>
> --
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> "geoengineering" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to geoengineering+unsubscr...@googlegroups.com.
> To view this discussion on the web visit
> https://groups.google.com/d/msgid/geoengineering/CAJ3C-04A%3DxrTYPQiJdaZ7hRzFTH93SxokB9o6Qh3Ha3a_tSxCg%40mail.gmail.com
> 
> .
>


-- 
With Best Wishes,

---
G. Bala
Professor
Center for Atmospheric and Oceanic Sciences
Indian Institute of Science
Bangalore - 560 012
India

Tel: +91 80 2293 3428; +91 80 2293 2505
Fax: +91 80 2360 0865; +91 80 2293 3425
Email: gb...@iisc.ac.in; bala@gmail.com
Web:http://dccc.iisc.ac.in/dr_govindasamy_bala_profile.html
---

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Re: [geo] A Model‐Based Investigation of Terrestrial Plant Carbon Uptake Response to Four Radiation Modification Approaches - Duan - 2020 - Journal of Geophysical Research: Atmospheres - Wiley Online

[Govindasamy Bala]

Andrew,

This is no contradiction between the Keith et al's commentary and this
paper. Keith et al.'s paper is about stocks and this JGR paper is about the
rate of flow of carbon between the atmosphere and the land biosphere
(flux). The stocks and fluxes can behave very differently. The cooling
caused by SRM reduces the rate of fluxing of carbon between the atmosphere
and plants but overall it helps to build the carbon stocks in biomass and
soils and hence reduce the atmospheric CO2.

Another good example for stocks and fluxes behaving very differently is the
change in precipitation (flux) and atmospheric water vapor (stock) under
global warming. It is well established now that precipitation increases at
the rate of 2-3% per deg warming while water vapor increases at the rate of
about 7% per deg warming.

Best,
Bala

On Wed, Apr 29, 2020 at 10:18 AM Andrew Lockley 
wrote:

> Poster's note: this has the opposite sign to other work on the subject eg
> https://keith.seas.harvard.edu/publications/solar-geoengineering-reduces-atmospheric-carbon-burden
>
> https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019JD031883
>
> Journal of Geophysical Research: AtmospheresVolume 125, Issue 9
> Research Article
> A Model‐Based Investigation of Terrestrial Plant Carbon Uptake Response to
> Four Radiation Modification Approaches
> Lei Duan Long Cao Govindasamy Bala Ken Caldeira
> First published:04 April 2020
> https://doi.org/10.1029/2019JD031883
>
> Abstract
> A number of radiation modification approaches have been proposed to
> counteract anthropogenic warming by intentionally altering Earth's
> shortwave or longwave fluxes. While several previous studies have examined
> the climate effect of different radiation modification approaches, only a
> few have investigated the carbon cycle response. Our study examines the
> response of plant carbon uptake to four radiation modification approaches
> that are used to offset the global mean warming caused by a doubling of
> atmospheric CO2. Using the National Center for Atmospheric Research
> Community Earth System Model, we performed simulations that represent four
> idealized radiation modification options: solar constant reduction, sulfate
> aerosol increase (SAI), marine cloud brightening, and cirrus cloud thinning
> (CCT). Relative to the high CO2 state, all these approaches reduce gross
> primary production (GPP) and net primary production (NPP). In high
> latitudes, decrease in GPP is mainly due to the reduced plant growing
> season length, and in low latitudes, decrease in GPP is mainly caused by
> the enhanced nitrogen limitation due to surface cooling. The simulated GPP
> for sunlit leaves decreases for all approaches. Decrease in sunlit GPP is
> the largest for SAI which substantially decreases direct sunlight, and the
> smallest for CCT, which increases direct sunlight that reaches the land
> surface. GPP for shaded leaves increases in SAI associated with a
> substantial increase in surface diffuse sunlight, and decreases in all
> other cases. The combined effects of CO2 increase and radiation
> modification result in increases in primary production, indicating the
> dominant role of the CO2 fertilization effect on plant carbon uptake.
>
> Plain Language Summary
> A number of radiation modification approaches have been proposed to
> intentionally alter Earth's radiation balance to counteract anthropogenic
> warming. However, only a few studies have analyzed the potential impact of
> these approaches on the terrestrial plant carbon cycle. Here, we simulate
> four idealized radiation modification approaches, which include direct
> reduction of incoming solar radiation, increase in stratospheric sulfate
> aerosols concentration, enhancement of marine low cloud albedo, and
> decrease in high‐level cirrus cloud cover, and analyze changes in plant
> photosynthesis and respiration. The first three approaches cool the earth
> by reducing incoming solar radiation, and the last approach allows more
> outgoing thermal radiation. These approaches are designed to offset the
> global mean warming caused by doubled atmospheric CO2. Compared to the high
> CO2 world, all approaches will limit plant growth due to induced surface
> cooling in high latitudes and will lead to reduced nitrogen supply in low
> latitudes, leading to an overall reduction in the plant carbon uptake over
> land. Different approaches also produce different changes in surface direct
> and diffuse sunlight, which has important implications for plant
> photosynthesis. Relative to the unperturbed climate, the combined effects
> of enhanced CO2 and radiation modifications leads to an increase in plants'
> primary production.
>
> --
> You received this message because you are subscribed to

Re: [geo] A Model‐Based Investigation of Terrestrial Plant Carbon Uptake Response to Four Radiation Modification Approaches - Duan - 2020 - Journal of Geophysical Research: Atmospheres - Wiley Online

[Govindasamy Bala]

Andrew,

You are absolutely right that "In situations where plants don't remain to
decomposition (agro forestry), there will be a loss of NPP"

Stock changes between two time periods are basically the integral of the
net fluxes between the two time periods. In a warming scenario, there is
net outward flux (and stocks decline) because the integrated respiratory
fluxes more than the integrated in flux of NPP. In SRM scenario, integrated
net flux is positive because the integrated respiratory fluxes are smaller
than integrated in flux.

Best,
Bala

On Wed, Apr 29, 2020 at 12:30 PM Andrew Lockley 
wrote:

> If the incoming flux decreases, the stock will reduce. To counter this,
> the outgoing flux must decrease by as much, or more. What is this
> corresponding decrease in the outward flux?
>
> Is it that decomposition of leaf litter, etc. is slowed by cooler and
> drier conditions?
>
> In situations where plants don't remain to decomposition (agro forestry),
> what will be the effect? Your results imply a loss of NPP.
>
> Andrew
>
> On Wed, 29 Apr 2020, 07:11 Govindasamy Bala,  wrote:
>
>> Andrew,
>>
>> This is no contradiction between the Keith et al's commentary and this
>> paper. Keith et al.'s paper is about stocks and this JGR paper is about the
>> rate of flow of carbon between the atmosphere and the land biosphere
>> (flux). The stocks and fluxes can behave very differently. The cooling
>> caused by SRM reduces the rate of fluxing of carbon between the atmosphere
>> and plants but overall it helps to build the carbon stocks in biomass and
>> soils and hence reduce the atmospheric CO2.
>>
>> Another good example for stocks and fluxes behaving very differently is
>> the change in precipitation (flux) and atmospheric water vapor (stock)
>> under global warming. It is well established now that
>> precipitation increases at the rate of 2-3% per deg warming while water
>> vapor increases at the rate of about 7% per deg warming.
>>
>> Best,
>> Bala
>>
>> On Wed, Apr 29, 2020 at 10:18 AM Andrew Lockley 
>> wrote:
>>
>>> Poster's note: this has the opposite sign to other work on the subject
>>> eg
>>> https://keith.seas.harvard.edu/publications/solar-geoengineering-reduces-atmospheric-carbon-burden
>>>
>>> https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019JD031883
>>>
>>> Journal of Geophysical Research: AtmospheresVolume 125, Issue 9
>>> Research Article
>>> A Model‐Based Investigation of Terrestrial Plant Carbon Uptake Response
>>> to Four Radiation Modification Approaches
>>> Lei Duan Long Cao Govindasamy Bala Ken Caldeira
>>> First published:04 April 2020
>>> https://doi.org/10.1029/2019JD031883
>>>
>>> Abstract
>>> A number of radiation modification approaches have been proposed to
>>> counteract anthropogenic warming by intentionally altering Earth's
>>> shortwave or longwave fluxes. While several previous studies have examined
>>> the climate effect of different radiation modification approaches, only a
>>> few have investigated the carbon cycle response. Our study examines the
>>> response of plant carbon uptake to four radiation modification approaches
>>> that are used to offset the global mean warming caused by a doubling of
>>> atmospheric CO2. Using the National Center for Atmospheric Research
>>> Community Earth System Model, we performed simulations that represent four
>>> idealized radiation modification options: solar constant reduction, sulfate
>>> aerosol increase (SAI), marine cloud brightening, and cirrus cloud thinning
>>> (CCT). Relative to the high CO2 state, all these approaches reduce gross
>>> primary production (GPP) and net primary production (NPP). In high
>>> latitudes, decrease in GPP is mainly due to the reduced plant growing
>>> season length, and in low latitudes, decrease in GPP is mainly caused by
>>> the enhanced nitrogen limitation due to surface cooling. The simulated GPP
>>> for sunlit leaves decreases for all approaches. Decrease in sunlit GPP is
>>> the largest for SAI which substantially decreases direct sunlight, and the
>>> smallest for CCT, which increases direct sunlight that reaches the land
>>> surface. GPP for shaded leaves increases in SAI associated with a
>>> substantial increase in surface diffuse sunlight, and decreases in all
>>> other cases. The combined effects of CO2 increase and radiation
>>> modification result in increases in primary production, indicating the
>>> dominant role of the 

Re: [geo] A Model‐Based Investigation of Terrestrial Plant Carbon Uptake Response to Four Radiation Modification Approaches - Duan - 2020 - Journal of Geophysical Research: Atmospheres - Wiley Online

[Govindasamy Bala]

Andrew,

"Are you saying that SRM effect on the carbon cycle still appears to be the
net removal of Atmospheric CO2?"

Yes, that is what the models say since this first 2008 PNAS paper by
Matthews and Ken on this topic which showed that CO2 levels would be lower
in SRM scenarios. This work finds that CO2 is reduced from 900 ppm to about
800 ppm in the atmosphere by 2100 in the A2 scenario. Not a lot as CO2
forcing goes up only  logarithmically with CO2 concentration

https://www.pnas.org/content/104/24/9949

There would be of course large uncertainties but I think the qualitative
result would not change across models. I would not go that far to say it is
a CDR technique. I would rather say it is a secondary benefit or a
co-benefit.

Bala

On Wed, Apr 29, 2020 at 1:42 PM Andrew Lockley 
wrote:

> So, to confirm:
> Are you saying that SRM effect on the carbon cycle still appears to be the
> net removal of Atmospheric CO2?
>
>  If so, SRM can legitimately be used as a CDR technique. It may therefore
> be eligible for Carbon credits, as per this paper.
> https://journals.sagepub.com/doi/abs/10.1177/1461452916630082
>
> On Wed, 29 Apr 2020, 08:56 Govindasamy Bala,  wrote:
>
>> Andrew,
>>
>> You are absolutely right that "In situations where plants don't remain to
>> decomposition (agro forestry), there will be a loss of NPP"
>>
>> Stock changes between two time periods are basically the integral of the
>> net fluxes between the two time periods. In a warming scenario, there is
>> net outward flux (and stocks decline) because the integrated respiratory
>> fluxes more than the integrated in flux of NPP. In SRM scenario, integrated
>> net flux is positive because the integrated respiratory fluxes are smaller
>> than integrated in flux.
>>
>> Best,
>> Bala
>>
>> On Wed, Apr 29, 2020 at 12:30 PM Andrew Lockley 
>> wrote:
>>
>>> If the incoming flux decreases, the stock will reduce. To counter this,
>>> the outgoing flux must decrease by as much, or more. What is this
>>> corresponding decrease in the outward flux?
>>>
>>> Is it that decomposition of leaf litter, etc. is slowed by cooler and
>>> drier conditions?
>>>
>>> In situations where plants don't remain to decomposition (agro
>>> forestry), what will be the effect? Your results imply a loss of NPP.
>>>
>>> Andrew
>>>
>>> On Wed, 29 Apr 2020, 07:11 Govindasamy Bala,  wrote:
>>>
>>>> Andrew,
>>>>
>>>> This is no contradiction between the Keith et al's commentary and this
>>>> paper. Keith et al.'s paper is about stocks and this JGR paper is about the
>>>> rate of flow of carbon between the atmosphere and the land biosphere
>>>> (flux). The stocks and fluxes can behave very differently. The cooling
>>>> caused by SRM reduces the rate of fluxing of carbon between the atmosphere
>>>> and plants but overall it helps to build the carbon stocks in biomass and
>>>> soils and hence reduce the atmospheric CO2.
>>>>
>>>> Another good example for stocks and fluxes behaving very differently is
>>>> the change in precipitation (flux) and atmospheric water vapor (stock)
>>>> under global warming. It is well established now that
>>>> precipitation increases at the rate of 2-3% per deg warming while water
>>>> vapor increases at the rate of about 7% per deg warming.
>>>>
>>>> Best,
>>>> Bala
>>>>
>>>> On Wed, Apr 29, 2020 at 10:18 AM Andrew Lockley <
>>>> andrew.lock...@gmail.com> wrote:
>>>>
>>>>> Poster's note: this has the opposite sign to other work on the subject
>>>>> eg
>>>>> https://keith.seas.harvard.edu/publications/solar-geoengineering-reduces-atmospheric-carbon-burden
>>>>>
>>>>> https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019JD031883
>>>>>
>>>>> Journal of Geophysical Research: AtmospheresVolume 125, Issue 9
>>>>> Research Article
>>>>> A Model‐Based Investigation of Terrestrial Plant Carbon Uptake
>>>>> Response to Four Radiation Modification Approaches
>>>>> Lei Duan Long Cao Govindasamy Bala Ken Caldeira
>>>>> First published:04 April 2020
>>>>> https://doi.org/10.1029/2019JD031883
>>>>>
>>>>> Abstract
>>>>> A number of radiation modification approaches have been proposed to
>>>>> counteract anthropogenic warming by inten

Re: [geo] A Model‐Based Investigation of Terrestrial Plant Carbon Uptake Response to Four Radiation Modification Approaches - Duan - 2020 - Journal of Geophysical Research: Atmospheres - Wiley Online

[Govindasamy Bala]

Andrew,
Technically, carbon and radiative forcing are equivalent to each other.
There are standard formulas to go from carbon to radiative forcing.
Bala

On Wed, Apr 29, 2020 at 4:45 PM Andrew Lockley 
wrote:

> The reason that the CDR aspect is significant is that there is already a
> way to monetise this, through voluntary carbon offsets. This was first
> suggested by Sargoni and I
> https://www.researchgate.net/publication/284534197_Environment_Policy_Solar_Radiation_Management_and_the_voluntary_carbon_market
>
> There's no such scheme available to monetise radiative forcing
>
> Andrew
>
> On Wed, 29 Apr 2020, 11:43 Govindasamy Bala,  wrote:
>
>> Andrew,
>>
>> "Are you saying that SRM effect on the carbon cycle still appears to be
>> the net removal of Atmospheric CO2?"
>>
>> Yes, that is what the models say since this first 2008 PNAS paper by
>> Matthews and Ken on this topic which showed that CO2 levels would be lower
>> in SRM scenarios. This work finds that CO2 is reduced from 900 ppm to about
>> 800 ppm in the atmosphere by 2100 in the A2 scenario. Not a lot as CO2
>> forcing goes up only  logarithmically with CO2 concentration
>>
>> https://www.pnas.org/content/104/24/9949
>>
>> There would be of course large uncertainties but I think the qualitative
>> result would not change across models. I would not go that far to say it is
>> a CDR technique. I would rather say it is a secondary benefit or a
>> co-benefit.
>>
>> Bala
>>
>> On Wed, Apr 29, 2020 at 1:42 PM Andrew Lockley 
>> wrote:
>>
>>> So, to confirm:
>>> Are you saying that SRM effect on the carbon cycle still appears to be
>>> the net removal of Atmospheric CO2?
>>>
>>>  If so, SRM can legitimately be used as a CDR technique. It may
>>> therefore be eligible for Carbon credits, as per this paper.
>>> https://journals.sagepub.com/doi/abs/10.1177/1461452916630082
>>>
>>> On Wed, 29 Apr 2020, 08:56 Govindasamy Bala,  wrote:
>>>
>>>> Andrew,
>>>>
>>>> You are absolutely right that "In situations where plants don't remain
>>>> to decomposition (agro forestry), there will be a loss of NPP"
>>>>
>>>> Stock changes between two time periods are basically the integral of
>>>> the net fluxes between the two time periods. In a warming scenario, there
>>>> is net outward flux (and stocks decline) because the integrated respiratory
>>>> fluxes more than the integrated in flux of NPP. In SRM scenario, integrated
>>>> net flux is positive because the integrated respiratory fluxes are smaller
>>>> than integrated in flux.
>>>>
>>>> Best,
>>>> Bala
>>>>
>>>> On Wed, Apr 29, 2020 at 12:30 PM Andrew Lockley <
>>>> andrew.lock...@gmail.com> wrote:
>>>>
>>>>> If the incoming flux decreases, the stock will reduce. To counter
>>>>> this, the outgoing flux must decrease by as much, or more. What is this
>>>>> corresponding decrease in the outward flux?
>>>>>
>>>>> Is it that decomposition of leaf litter, etc. is slowed by cooler and
>>>>> drier conditions?
>>>>>
>>>>> In situations where plants don't remain to decomposition (agro
>>>>> forestry), what will be the effect? Your results imply a loss of NPP.
>>>>>
>>>>> Andrew
>>>>>
>>>>> On Wed, 29 Apr 2020, 07:11 Govindasamy Bala, 
>>>>> wrote:
>>>>>
>>>>>> Andrew,
>>>>>>
>>>>>> This is no contradiction between the Keith et al's commentary and
>>>>>> this paper. Keith et al.'s paper is about stocks and this JGR paper is
>>>>>> about the rate of flow of carbon between the atmosphere and the land
>>>>>> biosphere (flux). The stocks and fluxes can behave very differently. The
>>>>>> cooling caused by SRM reduces the rate of fluxing of carbon between the
>>>>>> atmosphere and plants but overall it helps to build the carbon stocks in
>>>>>> biomass and soils and hence reduce the atmospheric CO2.
>>>>>>
>>>>>> Another good example for stocks and fluxes behaving very differently
>>>>>> is the change in precipitation (flux) and atmospheric water vapor (stock)
>>>>>> under global warming. It is well established now that
>>>>>> precipit

Re: [geo] A Model‐Based Investigation of Terrestrial Plant Carbon Uptake Response to Four Radiation Modification Approaches - Duan - 2020 - Journal of Geophysical Research: Atmospheres - Wiley Online

[Govindasamy Bala]

With so much uncertainty surrounding this small indirect carbon cycle
effects of SRM, I would not bother about monetizing calculations at
this time.
Bala

On Wed, Apr 29, 2020 at 5:49 PM Andrew Lockley 
wrote:

> That is indeed correct, but there is no accepted approach to financialise
> temporary radiative forcing. The effect on the carbon cycle would give a
> way to create a business model for SRM operations - as described in the
> papers I've sent.
>
> Andrew
>
> On Wed, 29 Apr 2020, 12:32 Govindasamy Bala,  wrote:
>
>> Andrew,
>> Technically, carbon and radiative forcing are equivalent to each other.
>> There are standard formulas to go from carbon to radiative forcing.
>> Bala
>>
>> On Wed, Apr 29, 2020 at 4:45 PM Andrew Lockley 
>> wrote:
>>
>>> The reason that the CDR aspect is significant is that there is already a
>>> way to monetise this, through voluntary carbon offsets. This was first
>>> suggested by Sargoni and I
>>> https://www.researchgate.net/publication/284534197_Environment_Policy_Solar_Radiation_Management_and_the_voluntary_carbon_market
>>>
>>> There's no such scheme available to monetise radiative forcing
>>>
>>> Andrew
>>>
>>> On Wed, 29 Apr 2020, 11:43 Govindasamy Bala,  wrote:
>>>
>>>> Andrew,
>>>>
>>>> "Are you saying that SRM effect on the carbon cycle still appears to be
>>>> the net removal of Atmospheric CO2?"
>>>>
>>>> Yes, that is what the models say since this first 2008 PNAS paper by
>>>> Matthews and Ken on this topic which showed that CO2 levels would be lower
>>>> in SRM scenarios. This work finds that CO2 is reduced from 900 ppm to about
>>>> 800 ppm in the atmosphere by 2100 in the A2 scenario. Not a lot as CO2
>>>> forcing goes up only  logarithmically with CO2 concentration
>>>>
>>>> https://www.pnas.org/content/104/24/9949
>>>>
>>>> There would be of course large uncertainties but I think the
>>>> qualitative result would not change across models. I would not go that far
>>>> to say it is a CDR technique. I would rather say it is a secondary benefit
>>>> or a co-benefit.
>>>>
>>>> Bala
>>>>
>>>> On Wed, Apr 29, 2020 at 1:42 PM Andrew Lockley <
>>>> andrew.lock...@gmail.com> wrote:
>>>>
>>>>> So, to confirm:
>>>>> Are you saying that SRM effect on the carbon cycle still appears to be
>>>>> the net removal of Atmospheric CO2?
>>>>>
>>>>>  If so, SRM can legitimately be used as a CDR technique. It may
>>>>> therefore be eligible for Carbon credits, as per this paper.
>>>>> https://journals.sagepub.com/doi/abs/10.1177/1461452916630082
>>>>>
>>>>> On Wed, 29 Apr 2020, 08:56 Govindasamy Bala, 
>>>>> wrote:
>>>>>
>>>>>> Andrew,
>>>>>>
>>>>>> You are absolutely right that "In situations where plants don't
>>>>>> remain to decomposition (agro forestry), there will be a loss of NPP"
>>>>>>
>>>>>> Stock changes between two time periods are basically the integral of
>>>>>> the net fluxes between the two time periods. In a warming scenario, there
>>>>>> is net outward flux (and stocks decline) because the integrated 
>>>>>> respiratory
>>>>>> fluxes more than the integrated in flux of NPP. In SRM scenario, 
>>>>>> integrated
>>>>>> net flux is positive because the integrated respiratory fluxes are 
>>>>>> smaller
>>>>>> than integrated in flux.
>>>>>>
>>>>>> Best,
>>>>>> Bala
>>>>>>
>>>>>> On Wed, Apr 29, 2020 at 12:30 PM Andrew Lockley <
>>>>>> andrew.lock...@gmail.com> wrote:
>>>>>>
>>>>>>> If the incoming flux decreases, the stock will reduce. To counter
>>>>>>> this, the outgoing flux must decrease by as much, or more. What is this
>>>>>>> corresponding decrease in the outward flux?
>>>>>>>
>>>>>>> Is it that decomposition of leaf litter, etc. is slowed by cooler
>>>>>>> and drier conditions?
>>>>>>>
>>>>>>> In situations where plants don't remain to decomposition (agro
>>>

Re: [geo] A Model‐Based Investigation of Terrestrial Plant Carbon Uptake Response to Four Radiation Modification Approaches - Duan - 2020 - Journal of Geophysical Research: Atmospheres - Wiley Online

[Govindasamy Bala]

Renaud,

You are not wrong.

The SRM world has two forcings; one from increased CO2 and the other from
sunlight reduction. The sunlight reduction alone offsets the warming from
CO2 and causes a slight reduction in NPP. However, the CO2-fertilization
effect (and the associated very large (??) increase in NPP) is mostly not
offset by the sunlight reduction. The CO2-fertilization effect (and ocean
acidification) are the carbon cycle effects of CO2 increase that are mostly
not offset by SRM.

Hence, relative to the control climate, NPP is larger in the SRM world but
NPP is slightly less relative to the warmer climate. Yes, what you
comparing the SRM world with is extremely important in interpreting these
results. Hope this helps.

Bala

On Sun, May 3, 2020 at 4:11 PM Renaud de RICHTER 
wrote:

> Dear Andrew and Bala,
>
>
> All your discussion you had during this post is very difficult to
> understand.
>
>
> Bala and the other authors of the article cited in the subject found with
> their model that a 2 X CO2 by the end of century will enhance gross primary
> production (GPP) and net primary production (NPP).
>
> See *Table 1*: "*Changes in key climate and carbon variables over land
> for the 2 × CO2 case relative to 1 × CO2 case, and radiation modification
> cases relative to the 2 × CO2 case*".
>
>-  under 2 X CO2 => GPP (+33.1 GTC/yr) and NPP (+7.9 GTC/yr) mainly by
>the fertilizing effect of atmospheric CO2.
>-  meanwhile SRM / SAI will decrease GPP (-14.7 GTC/yr) and NPP (-2.1
>GTC/yr) mainly by cooling effect.
>
> In the abstract it is written "*Relative to the high CO2 state, all these
> approaches reduce gross primary production (GPP) and net primary production
> (NPP).*"
>
>
> So it looks like the opposite to your statement..." *SRM effect on the
> carbon cycle still appears to be the net removal of Atmospheric CO2.*..".
>
>
> Where am I wrong?
>
> Thanks!
>
>
> Bw,
>
> Renaud
>
>
> Le mer. 29 avr. 2020 à 17:37, Andrew Lockley  a
> écrit :
>
>> I would recommend that you consider the numbers on this, before forming a
>> firm view. To order of magnitude, 1t S delivered is $1000 (mileage may
>> vary). If 1Mt a year is roughly enough to offset the RF of global warming,
>> then about 10pc of that is a CO2 effect. That's about 0.1 millionth of
>> global warming per t of S, on an annual basis - according to your figures.
>> Assuming we sustain the intervention for a century, that's $100k for
>> maintenance of that 1t, for a century - again offsetting 0.1 millionth.
>>
>> Offsets go for about $3/t
>> https://www.energysage.com/other-clean-options/carbon-offsets/costs-and-benefits-carbon-offsets/
>>
>> There's about 1Tt of CO2 to offset - ie $3T, using the offset price. 0.1
>> millionths of that is $300k
>>
>> So your $100k costs gives you a $300k return.
>>
>> Not bad, unless (as usual) I've fluffed my 4th grade math.
>>
>> Andrew
>>
>> On Wed, 29 Apr 2020, 15:44 Govindasamy Bala,  wrote:
>>
>>> With so much uncertainty surrounding this small indirect carbon cycle
>>> effects of SRM, I would not bother about monetizing calculations at
>>> this time.
>>> Bala
>>>
>>> On Wed, Apr 29, 2020 at 5:49 PM Andrew Lockley 
>>> wrote:
>>>
>>>> That is indeed correct, but there is no accepted approach to
>>>> financialise temporary radiative forcing. The effect on the carbon cycle
>>>> would give a way to create a business model for SRM operations - as
>>>> described in the papers I've sent.
>>>>
>>>> Andrew
>>>>
>>>> On Wed, 29 Apr 2020, 12:32 Govindasamy Bala, 
>>>> wrote:
>>>>
>>>>> Andrew,
>>>>> Technically, carbon and radiative forcing are equivalent to each
>>>>> other. There are standard formulas to go from carbon to radiative forcing.
>>>>> Bala
>>>>>
>>>>> On Wed, Apr 29, 2020 at 4:45 PM Andrew Lockley <
>>>>> andrew.lock...@gmail.com> wrote:
>>>>>
>>>>>> The reason that the CDR aspect is significant is that there is
>>>>>> already a way to monetise this, through voluntary carbon offsets. This 
>>>>>> was
>>>>>> first suggested by Sargoni and I
>>>>>> https://www.researchgate.net/publication/284534197_Environment_Policy_Solar_Radiation_Management_and_the_voluntary_carbon_market
>>>>>>
>>>>>> There's no such scheme available to monetise radiative

Re: [geo] A Model‐Based Investigation of Terrestrial Plant Carbon Uptake Response to Four Radiation Modification Approaches - Duan - 2020 - Journal of Geophysical Research: Atmospheres - Wiley Online

[Govindasamy Bala]

Andrew,

In the case of CDR like DAC, one can immediately know much carbon is
extracted and pricing is easy.  In the case of carbon stocks increase due
to SRM, attribution of the stock increase to SRM would be almost an
impossible task in the real world.

Bala

On Wed, Apr 29, 2020 at 9:07 PM Andrew Lockley 
wrote:

> I would recommend that you consider the numbers on this, before forming a
> firm view. To order of magnitude, 1t S delivered is $1000 (mileage may
> vary). If 1Mt a year is roughly enough to offset the RF of global warming,
> then about 10pc of that is a CO2 effect. That's about 0.1 millionth of
> global warming per t of S, on an annual basis - according to your figures.
> Assuming we sustain the intervention for a century, that's $100k for
> maintenance of that 1t, for a century - again offsetting 0.1 millionth.
>
> Offsets go for about $3/t
> https://www.energysage.com/other-clean-options/carbon-offsets/costs-and-benefits-carbon-offsets/
>
> There's about 1Tt of CO2 to offset - ie $3T, using the offset price. 0.1
> millionths of that is $300k
>
> So your $100k costs gives you a $300k return.
>
> Not bad, unless (as usual) I've fluffed my 4th grade math.
>
> Andrew
>
> On Wed, 29 Apr 2020, 15:44 Govindasamy Bala,  wrote:
>
>> With so much uncertainty surrounding this small indirect carbon cycle
>> effects of SRM, I would not bother about monetizing calculations at
>> this time.
>> Bala
>>
>> On Wed, Apr 29, 2020 at 5:49 PM Andrew Lockley 
>> wrote:
>>
>>> That is indeed correct, but there is no accepted approach to
>>> financialise temporary radiative forcing. The effect on the carbon cycle
>>> would give a way to create a business model for SRM operations - as
>>> described in the papers I've sent.
>>>
>>> Andrew
>>>
>>> On Wed, 29 Apr 2020, 12:32 Govindasamy Bala,  wrote:
>>>
>>>> Andrew,
>>>> Technically, carbon and radiative forcing are equivalent to each other.
>>>> There are standard formulas to go from carbon to radiative forcing.
>>>> Bala
>>>>
>>>> On Wed, Apr 29, 2020 at 4:45 PM Andrew Lockley <
>>>> andrew.lock...@gmail.com> wrote:
>>>>
>>>>> The reason that the CDR aspect is significant is that there is already
>>>>> a way to monetise this, through voluntary carbon offsets. This was first
>>>>> suggested by Sargoni and I
>>>>> https://www.researchgate.net/publication/284534197_Environment_Policy_Solar_Radiation_Management_and_the_voluntary_carbon_market
>>>>>
>>>>> There's no such scheme available to monetise radiative forcing
>>>>>
>>>>> Andrew
>>>>>
>>>>> On Wed, 29 Apr 2020, 11:43 Govindasamy Bala, 
>>>>> wrote:
>>>>>
>>>>>> Andrew,
>>>>>>
>>>>>> "Are you saying that SRM effect on the carbon cycle still appears to
>>>>>> be the net removal of Atmospheric CO2?"
>>>>>>
>>>>>> Yes, that is what the models say since this first 2008 PNAS paper by
>>>>>> Matthews and Ken on this topic which showed that CO2 levels would be 
>>>>>> lower
>>>>>> in SRM scenarios. This work finds that CO2 is reduced from 900 ppm to 
>>>>>> about
>>>>>> 800 ppm in the atmosphere by 2100 in the A2 scenario. Not a lot as CO2
>>>>>> forcing goes up only  logarithmically with CO2 concentration
>>>>>>
>>>>>> https://www.pnas.org/content/104/24/9949
>>>>>>
>>>>>> There would be of course large uncertainties but I think the
>>>>>> qualitative result would not change across models. I would not go that 
>>>>>> far
>>>>>> to say it is a CDR technique. I would rather say it is a secondary 
>>>>>> benefit
>>>>>> or a co-benefit.
>>>>>>
>>>>>> Bala
>>>>>>
>>>>>> On Wed, Apr 29, 2020 at 1:42 PM Andrew Lockley <
>>>>>> andrew.lock...@gmail.com> wrote:
>>>>>>
>>>>>>> So, to confirm:
>>>>>>> Are you saying that SRM effect on the carbon cycle still appears to
>>>>>>> be the net removal of Atmospheric CO2?
>>>>>>>
>>>>>>>  If so, SRM can legitimately be used as a CDR technique. It may
>>>>>>> therefore be

Re: [geo] A Model‐Based Investigation of Terrestrial Plant Carbon Uptake Response to Four Radiation Modification Approaches - Duan - 2020 - Journal of Geophysical Research: Atmospheres - Wiley Online

[Govindasamy Bala]

Dear Stephen,

Here too, the attribution would be a big challenge. In this case the
challenge would be because of the presence of large internal variability in
the climate system, particularly on regional scales.
Bala

On Sun, May 3, 2020 at 10:40 PM Stephen Salter  wrote:

> Dear Bala
>
>  . . . .  However countries facing expensive damage from hurricanes and
> typhoons could measure surface temperatures  in surrounding seas and pay to
> have them reduced to more acceptable values.  I understand the 26.5 C is
> nice. Rough calculations appear to give extremely attractive returns on
> investment at least according to my assumptions.  I can send the equations
> to you and anyone else who  would like them and would be grateful for any
> more accurate than my own.
>
> Stephen
>
>
> Emeritus Professor of Engineering Design. School of Engineering,
> University of Edinburgh, Mayfield Road, Edinburgh EH9 3DW, Scotland
> s.sal...@ed.ac.uk, Tel +44 (0)131 662 1180 WWW.homepages.ed.ac.uk/shs,
> YouTube Jamie Taylor Power for Change
>
> On 03/05/2020 16:02, Govindasamy Bala wrote:
>
> Andrew,
>
> In the case of CDR like DAC, one can immediately know much carbon is
> extracted and pricing is easy.  In the case of carbon stocks increase due
> to SRM, attribution of the stock increase to SRM would be almost an
> impossible task in the real world.
>
> Bala
>
> On Wed, Apr 29, 2020 at 9:07 PM Andrew Lockley 
> wrote:
>
>> I would recommend that you consider the numbers on this, before forming a
>> firm view. To order of magnitude, 1t S delivered is $1000 (mileage may
>> vary). If 1Mt a year is roughly enough to offset the RF of global warming,
>> then about 10pc of that is a CO2 effect. That's about 0.1 millionth of
>> global warming per t of S, on an annual basis - according to your figures.
>> Assuming we sustain the intervention for a century, that's $100k for
>> maintenance of that 1t, for a century - again offsetting 0.1 millionth.
>>
>> Offsets go for about $3/t
>> https://www.energysage.com/other-clean-options/carbon-offsets/costs-and-benefits-carbon-offsets/
>>
>> There's about 1Tt of CO2 to offset - ie $3T, using the offset price. 0.1
>> millionths of that is $300k
>>
>> So your $100k costs gives you a $300k return.
>>
>> Not bad, unless (as usual) I've fluffed my 4th grade math.
>>
>> Andrew
>>
>> On Wed, 29 Apr 2020, 15:44 Govindasamy Bala,  wrote:
>>
>>> With so much uncertainty surrounding this small indirect carbon cycle
>>> effects of SRM, I would not bother about monetizing calculations at
>>> this time.
>>> Bala
>>>
>>> On Wed, Apr 29, 2020 at 5:49 PM Andrew Lockley 
>>> wrote:
>>>
>>>> That is indeed correct, but there is no accepted approach to
>>>> financialise temporary radiative forcing. The effect on the carbon cycle
>>>> would give a way to create a business model for SRM operations - as
>>>> described in the papers I've sent.
>>>>
>>>> Andrew
>>>>
>>>> On Wed, 29 Apr 2020, 12:32 Govindasamy Bala, 
>>>> wrote:
>>>>
>>>>> Andrew,
>>>>> Technically, carbon and radiative forcing are equivalent to each
>>>>> other. There are standard formulas to go from carbon to radiative forcing.
>>>>> Bala
>>>>>
>>>>> On Wed, Apr 29, 2020 at 4:45 PM Andrew Lockley <
>>>>> andrew.lock...@gmail.com> wrote:
>>>>>
>>>>>> The reason that the CDR aspect is significant is that there is
>>>>>> already a way to monetise this, through voluntary carbon offsets. This 
>>>>>> was
>>>>>> first suggested by Sargoni and I
>>>>>> https://www.researchgate.net/publication/284534197_Environment_Policy_Solar_Radiation_Management_and_the_voluntary_carbon_market
>>>>>>
>>>>>> There's no such scheme available to monetise radiative forcing
>>>>>>
>>>>>> Andrew
>>>>>>
>>>>>> On Wed, 29 Apr 2020, 11:43 Govindasamy Bala, 
>>>>>> wrote:
>>>>>>
>>>>>>> Andrew,
>>>>>>>
>>>>>>> "Are you saying that SRM effect on the carbon cycle still appears to
>>>>>>> be the net removal of Atmospheric CO2?"
>>>>>>>
>>>>>>> Yes, that is what the models say since this first 2008 PNAS paper by
>>>>>>> Matthews a

Re: [geo] Actual, live, real, SAI happening right now?

[Govindasamy Bala]

SAI option involves sulfate aerosols (scattering aerosols), not black
carbon aerosols or smoke which are absorbing aerosolsI believe BC
aerosols in large quantities in the stratosphere would have devastating
consequences for stratospheric ozone. Also, there is no ocean fertilization
effect from smoke particles.
Bala

On Wed, Sep 16, 2020 at 4:42 PM Jessica Gurevitch <
jessica.gurevi...@stonybrook.edu> wrote:

> I have rarely posted to this group (I'm a lurker, I read your posts!) so I
> hope this goes through.
> It occurs to me that we have an actual, physical, real SAI "experiment"
> going on right now with the very high smoke over the eastern US from the
> catastrophic western wildfires. Skies are gray and it is really cool here
> on the East Coast. Can this situation be used in any way to measure
> anything valuable from a real physical occurrence of SRM? How similar or
> different is this from any of the proposed SAI schemes? Is anyone using
> this crazy opportunity to better understand some of the predictions? Or am
> I way off base here? If nothing else, it seems as if it can be used as
> a public demonstration of "what if we implemented SAI". But feel free to
> shoot this down if I am completely misunderstanding what's happening with
> this smoke in the stratosphere.
> Where are the particles going to fall, is that predicted yet? Is this
> going to have a fertilization effect on the Atlantic Ocean?
> Just wondering about all of this to displace my severe anxiety about the
> fires (my son in Oregon evacuated but just came back to his house), the
> election, the pandemic, teaching online, all of that fun stuff...
>
> Jessica
>
> ~~
> Jessica Gurevitch
> Distinguished Professor
> Department of Ecology and Evolution
> Stony Brook University
> Stony Brook, NY 11794-5245 USA
> ~~
>
> --
> You received this message because you are subscribed to the Google Groups
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> 
> .
>


-- 
With Best Wishes,

---
G. Bala
Professor
Center for Atmospheric and Oceanic Sciences
Indian Institute of Science
Bangalore - 560 012
India

Tel: +91 80 2293 3428; +91 80 2293 2505
Fax: +91 80 2360 0865; +91 80 2293 3425
Email: gb...@iisc.ac.in; bala@gmail.com
Web:http://dccc.iisc.ac.in/dr_govindasamy_bala_profile.html
---

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[geo] SG and Tropical Monsoons

[Govindasamy Bala]

Dear All,

In this paper that came out last week in Climate Dynamics
, we looked at the changes in
mean precipitation in tropical monsoon regions for sulfate injections at
different latitudes.

Key message: India could experience persistent droughts if aerosols are
injected at 15 or 30 deg N. The result is interpreted from planetary
energetics and interhemispheric asymmetry in energy balance.

Many of you may be aware that Ben Kravitz, Doug, Simone and others have
worked on ideas such as controlled injections at several locations
simultaneously to avoid such catastrophes, but I am not sure we can really
have such precise control on the climate system

-- 
With Best Wishes,

---
G. Bala
Professor
Center for Atmospheric and Oceanic Sciences
Indian Institute of Science
Bangalore - 560 012
India

Tel: +91 80 2293 3428; +91 80 2293 2505
Fax: +91 80 2360 0865; +91 80 2293 3425
Email: gb...@iisc.ac.in; bala@gmail.com
Google Scholar 
---

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Re: [geo] Solar geoengineering to cool the planet: Not if, but when

[Govindasamy Bala]

'Solar geoengineering is not happening yet, but there has been quite a lot
of research in that direction and the technology is essentially ready to go'

Is the technology really ready? Looks like we have a controversy on this
notion of "technological readiness" too.



On Fri, May 6, 2022 at 2:30 AM Geoeng Info  wrote:

>
> https://www.irishtimes.com/news/science/solar-geoengineering-to-cool-the-planet-not-if-but-when-1.4859423
>
> Solar geoengineering to cool the planet: Not if, but when
>
> Controlling the world’s changing climate with the use of geoengineering is
> thought to be fraught with risks. Imagine a rogue actor taking control of
> the climate, impacting the weather, storms, and rainfall with implications
> for the global economy and society in general – the stuff of James Bond
> 
>  villains
> in the Putin era.
>
> But many researchers and politicians argue geoengineering as a very real
> solution. Solar geoengineering in particular, the notion of cooling Earth
> by reflecting sunlight back into space, is increasing in popularity. But
> this ambition would require huge global coordination.
>
> Austrian researcher Gernot Wagner
> 
>  is
> a climate economist, academic and author who describes himself as a
> reluctant proponent of geoengineering. He is the founding co-director of
> Harvard’s Solar Geoengineering Research
> 
>  Programme.
>
> In his recent book, Geoengineering: The Gamble, he provides his take on
> the possible benefits and risks of various approaches, especially the
> so-called “moral hazard”; that researching or even discussing
> geoengineering would undermine the race to cut carbon emissions in the
> first place.
>
> Despite those risks, he argues that an era of solar geoengineering may be
> an inevitability – not a question of if, but when – and a crucial component
> of what he terms climate economics. This interview was conducted via video
> call.
>
> *What is a climate economist?*
>
> A walking living oxymoron, right? Not too long ago, when I told people I
> am a climate economist, the first response was generally one of confusion.
> You can either worry about interest rates and unemployment, or you worry
> about birds, bees and the climate scenario – but not both.
>
> I don’t know what changed over the past few years. Obviously, it depends
> on the country and I feel that Ireland  and
> some other countries European nations grasped this earlier, but in many
> other places, like here in the US, that change happened much more recently,
> where suddenly it’s become completely obvious that the climate is such an
> all-encompassing issue that it is completely related to the economy.
>
> So let’s call the climate economist the person who can help guide market
> forces in the right direction to tackle the challenges of the 21st century.
> Climate economics is about focusing on pricing climate risk and figuring
> out what to do about it.
>
> Geoengineering is a kind of stepchild of climate policy, and frankly it
> should be, for good reason. Step one in climate policy is to coordinate how
> we cut net carbon emissions to zero. Step two is adapting properly –
> adapting to what’s already in store. That’s where geoengineering comes in.
>
> We’ve been beating the drum about cutting carbon emissions forever but we
> haven’t solved climate change yet. So geoengineering is this notion of
> altering the atmosphere so as to reduce the impact of a rapidly changing
> climate. Carbon capture is one example where carbon is literally sucked out
> of the air.
>
> It’s technically possible and is already being used at small scales, but
> is very expensive. A cheaper solution, but one which is more controversial
> – and is the focus of most of my work – is solar geoengineering, an
> approach which aims to reflect sunlight, that is to say, energy and
> radiation, back into space in an attempt to cool the planet.
>
> *How does solar geoengineering work in practice?*
>
> Well, the idea is to deliberately release millions of tonnes of very small
> reflective particles into the lower stratosphere, which act together to
> reflect just enough sunlight to cool the Earth to a desired level. We know
> that it will work because volcanoes have been doing this since time began.
>
> 'Solar geoengineering is not happening yet, but there has been quite a lot
> of research in that direction and the technology is essentially ready to go'
>
> When a volcano erupts, it sends up all these particles into the
> atmosphere, eventually causing a cooling below due to their reflective
> properties. The difference in the case of solar geoengineering, of course,
> is that there is no violent explosion. It’s impor

Re: [geo] Climate model bias

[Govindasamy Bala]

I am not at all surprised by the regional bias of this magnitude in the
previous generation of models. The paper says this bias is reduced in CMIP6
models to about 10 Wm-2. These biases are related to how global models
"represent" cloud properties such as cloud liquid water, liquid cloud
fraction, and total cloud fraction which have biases of about 10-20%. I
would never expect global models with a resolution of about 100 km to
reproduce accurately these subgrid-scale variables.  GCMs were not designed
to "simulate" clouds which are "represented" through parameterizations
using various "assumptions". GCMs are designed to only simulate large-scale
(~ 1000 km) features well. Models are only our attempt to explain the real
world and no model exists today in any branch of science that can explain
everything in that branch of science.

There is nothing here to admire or find fault with modellers.  It is just
that the problem is too complex with too many degrees of freedom. In fact,
I am happy we have made unbelievable progress in the last 3-4 decades. It
is a work in progress (like modelling in any branch of science) and I do
not expect an end game anytime soon.
Cheers,
Bala

On Thu, Sep 22, 2022 at 8:11 PM Stephen Salter  wrote:

> Hi All
>
> A paper at
> https://link.springer.com/content/pdf/10.1007/s00376-022-2036-z.pdf
>
> says that there are significant biases in simulated cloud physical
> properties over the Southern Ocean.
>
> Section 5 mentions a mean bias of “more than 30 Watts per square metre”
> lots more than I thought was the problem.
>
> However it is not clear, at least to an engineer, whether it means plus or
> minus 30 watts per square metre.
>
> This does not increase my admiration for climate modellers. Please help.
>
> Stephen
>
> *Professor of Engineering Design*
>
> *School of Engineering*
>
> *University of Edinburgh*
>
> *Mayfield Road*
>
> *Edinburgh EH9 3DW*
>
> *Scotland*
>
> *0131 650 5704 or 662 1180*
>
>
> The University of Edinburgh is a charitable body, registered in Scotland,
> with registration number SC005336. Is e buidheann carthannais a th’ ann an
> Oilthigh Dhùn Èideann, clàraichte an Alba, àireamh clàraidh SC005336.
>
> --
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> 
> .
>


-- 
With Best Wishes,

---
G. Bala
Professor
Center for Atmospheric and Oceanic Sciences
Indian Institute of Science
Bangalore - 560 012
India

Tel: +91 80 2293 3428; +91 80 2293 2505
Fax: +91 80 2360 0865; +91 80 2293 3425
Email: gb...@iisc.ac.in; bala@gmail.com
Google Scholar 
---

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[geo] FF vs LULCC emissions

[Govindasamy Bala]

https://doi.org/10.1088/1748-9326/ac69fd

This ERL paper demonstrating the fundamental difference between Fossil Fuel
emissions and LULCC was published some months back, but I am not sure it
was posted here.

*Key message:* FF emissions and LULCC are fundamentally different. Hence,
in terms of climate benefits, offsetting FF emissions with afforestation is
scientifically flawed.

This is textbook stuff but good to demonstrate the concept using a
comprehensive Earth system model.

https://doi.org/10.1088/1748-9326/ac69fd


*Contrasting climate and carbon-cycle consequences of fossil-fueluse versus
deforestation disturbance*

*Abstract*
Carbon dioxide emissions from deforestation disturbance (e.g.
clear-cutting, forest fires) are in the same units as carbon dioxide
emissions from fossil fuels. However, if the forest is allowed to
regrow, there is a large difference between the climate effects of that
forest disturbance and the climate effects of fossil CO2. In this study,
using a set of idealized global climate-carbon model simulations with equal
amounts of CO2 emissions, we show that on century to millennial timescales
the response of the climate system to fossil-fuel burning versus
deforestation disturbance are vastly different. We performed two 1000-year
simulations where we added abrupt emissions of about 600 PgC to the
preindustrial state as a consequence of either fossil fuel use or
deforestation disturbance with vegetation regrowth. In the fossil fuel
simulations, after 1000 years, about 20% of the initial atmospheric CO2
concentration perturbation remains in the atmosphere and the climate is
about 1 ◦C warmer compared to the preindustrial state. In contrast, in the
case of deforestation with regrowth, after 1000 years, atmospheric CO2
concentration returns close to preindustrial values, because deforested
land will typically recover its carbon over the decades and centuries in
the absence of further human intervention. These results highlight the
differences in the degree of long-term commitment associated with fossil
fuel versus deforestation emissions.


-- 
With Best Wishes,

---
G. Bala
Professor
Center for Atmospheric and Oceanic Sciences
Indian Institute of Science
Bangalore - 560 012
India

Tel: +91 80 2293 3428; +91 80 2293 2505
Fax: +91 80 2360 0865; +91 80 2293 3425
Email: gb...@iisc.ac.in; bala@gmail.com
Google Scholar 
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[geo] Re: [CDR] FF vs LULCC emissions

[Govindasamy Bala]

Dan,

Good question. This is a "highly idealized" study to mainly illustrate the
point that the *"long-term"* consequences of the two emission sources are
very different. The key message we wanted to convey was that the FF
emissions add external carbon to the climate system (atmosphere, land
biosphere and ocean) while LULCC fluxes are just an internal arrangement of
carbon in the climate system. A fraction of the externally added carbon
would stay in the atmosphere for millennia while internally added carbon to
the atmosphere could be completely removed in the absence of further human
intervention.

It is not always true that deforested area remains deforested. A good
example is the abandoned agricultural areas in the mid-latitudes where
there is regrowth of forests. I am sure we can endlessly argue about the
fate of deforested land and the realism of the scenario employed in our
study. The key scientific message should not be lost by giving too much
importance to specific scenarios.
Cheers
Bala

On Thu, Oct 6, 2022 at 1:16 PM Daniel Nepstad 
wrote:

> Thanks for sharing.
>
> Your study assumes that deforestation is followed by forest regrowth,
> correct?  But most deforestation is followed by the establishment of
> permanent cropland or grazing land. This is consistent with the growing
> demand of the human population for food, feed and fuel from the land. And
> where forest is allowed to regrow, it is often subject to further
> disturbance (fire, logging, thinning) that prevent it from recovering
> pre-clearing carbon stocks.
>
> Could you explain the rationale for assuming that all deforestation is
> followed by regrowth?
>
> Kind regards,
>
> Dan
>
>
>
> On Oct 6, 2022, at 6:55 AM, Govindasamy Bala  wrote:
>
> https://doi.org/10.1088/1748-9326/ac69fd
>
> This ERL paper demonstrating the fundamental difference between Fossil
> Fuel emissions and LULCC was published some months back, but I am not sure
> it was posted here.
>
> *Key message:* FF emissions and LULCC are fundamentally different. Hence,
> in terms of climate benefits, offsetting FF emissions with afforestation is
> scientifically flawed.
>
> This is textbook stuff but good to demonstrate the concept using a
> comprehensive Earth system model.
>
> https://doi.org/10.1088/1748-9326/ac69fd
>
>
> *Contrasting climate and carbon-cycle consequences of fossil-fueluse
> versus deforestation disturbance*
>
> *Abstract*
> Carbon dioxide emissions from deforestation disturbance (e.g.
> clear-cutting, forest fires) are in the same units as carbon dioxide
> emissions from fossil fuels. However, if the forest is allowed to
> regrow, there is a large difference between the climate effects of that
> forest disturbance and the climate effects of fossil CO2. In this study,
> using a set of idealized global climate-carbon model simulations with equal
> amounts of CO2 emissions, we show that on century to millennial timescales
> the response of the climate system to fossil-fuel burning versus
> deforestation disturbance are vastly different. We performed two 1000-year
> simulations where we added abrupt emissions of about 600 PgC to the
> preindustrial state as a consequence of either fossil fuel use or
> deforestation disturbance with vegetation regrowth. In the fossil fuel
> simulations, after 1000 years, about 20% of the initial atmospheric CO2
> concentration perturbation remains in the atmosphere and the climate is
> about 1 ◦C warmer compared to the preindustrial state. In contrast, in the
> case of deforestation with regrowth, after 1000 years, atmospheric CO2
> concentration returns close to preindustrial values, because deforested
> land will typically recover its carbon over the decades and centuries in
> the absence of further human intervention. These results highlight the
> differences in the degree of long-term commitment associated with fossil
> fuel versus deforestation emissions.
>
>
> --
> With Best Wishes,
>
> ---
> G. Bala
> Professor
> Center for Atmospheric and Oceanic Sciences
> Indian Institute of Science
> Bangalore - 560 012
> India
>
> Tel: +91 80 2293 3428; +91 80 2293 2505
> Fax: +91 80 2360 0865; +91 80 2293 3425
> Email: gb...@iisc.ac.in; bala@gmail.com
> Google Scholar <https://scholar.google.com/citations?user=eurjQPwJ>
> ---
>
>
> --
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> To view this discu

Re: [geo] Re: Stratospheric warming, SRM and aerosol injection events

[Govindasamy Bala]

Besides the effects on stratospheric circulation and chemistry,
stratospheric warming caused by sulfate aerosols reduces the effectiveness
of what we are trying to achieve. The main intent is to increase sunlight
reflection. Part of this cooling effect is offset by stratospheric warming.
In a 2019 ESD paper, we show this by prescribing volcanic aerosols at 16,
19, and 22 km. In all these 3 cases, there is stratospheric warming.
However, in the case of 16km which is close to the troposphere, the
stratospheric warming leads to more water vapor in the stratosphere which
could further offset the originally intended cooling.

https://doi.org/10.5194/esd-10-885-2019

Cheers,
Bala

On Wed, Oct 19, 2022 at 8:52 AM 'Adrian Hindes' via geoengineering <
geoengineering@googlegroups.com> wrote:

> I'm not an expert on atmospheric dynamics, but am aware of some relevant
> papers in that general direction.
>
> Gao et al. (2021) looked at "practical" SAI using solar powered lofting
> from black carbon particles, partly inspired by the dynamics seen from
> large bushfires: https://www.science.org/doi/10.1126/sciadv.abe3416
>
> More broadly related, Christian et al. (2019) looked at the radiative
> forcing and stratospheric warming impacts of pyrocumulonimbus clouds:
> https://doi.org/10.1029/2019GL082360
> Along the same lines, Peterson et al. (2021) looked specifically at the
> Black Summer bushfires in Australia from 2019-20:
> http://www.nature.com/articles/s41612-021-00192-9
>
> Similar methods from those studies would presumably be applicable to
> studying SAI injection, and/or the potential dynamics between artificially
> injected sulphur (or other) aerosols with stratospheric warming events,
> pyroCb clouds and the like. I imagine there would be quite a lot of
> complexity with potentially compounding effects, maybe increasing aerosol
> lifetime, mixing and regional hydroclimatic changes, etc.
>
> Speaking of which, Simpson et al. (2019) specifically looked at the
> regional hydroclimatic effects of SAI, and how stratospheric heating plays
> into it: 10.1029/2019JD031093 .
>
> My understanding from reading that paper and others is stratospheric
> heating dynamics of SAI is one of those areas where there's still quite a
> lot of uncertainty, and an area of active research. Maybe other folks in
> the group here who have more experience with ESMs and atmospheric dynamics
> can comment further. I know the perspective paper by Ben Kravitz and Doug
> MacMartin  on uncertainty in
> solar geo research picked out stratospheric heating impacts on tropospheric
> and surface climate as one of the key outstanding uncertainties.
>
> On Wednesday, 19 October 2022 at 6:35:43 am UTC+11 ggfut...@gmail.com
> wrote:
>
>> Hi all,
>> Do people know of the impact of stratospheric warming that SRM causes on
>> the injection of other aerosols into the stratosphere, say from wildfire
>> events or volcanic eruptions? Like, how does a warm stratosphere effect how
>> these aerosols rise into the stratosphere and the dynamics of them within
>> the stratosphere
>> Best Wishes
>> Gideon
>>
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> 
> .
>


-- 
With Best Wishes,

---
G. Bala
Professor
Center for Atmospheric and Oceanic Sciences
Indian Institute of Science
Bangalore - 560 012
India

Tel: +91 80 2293 3428; +91 80 2293 2505
Fax: +91 80 2360 0865; +91 80 2293 3425
Email: gb...@iisc.ac.in; bala@gmail.com
Google Scholar 
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[geo] Geoengineering session @ IUGG 2023

[Govindasamy Bala]

   -
   - Abstract submission
   
<http://links.c-in.eu/ls/click?upn=T7eHPghXgHXChvPFXj9jF1tnKdZ-2FbOF-2B7oR7I2RmVJnZKYoUQIYRgPcYd16aLLzxPZdu9OWUuR7d3wvtWSf0lQ-3D-3Dwohv_R5xmhT1hyWYuWxjEu6rnxE8ohXQ2KDT5l1G-2FSzJNS5tjv-2B5JWZ2dTXhUrJuZAGSvFbHRqwMzz-2BZOcK189pMvNwsqxGCO2rWvoPznf-2FbwFue4q9eH8srk6SsTfoT2fUHb8BPsxPH2H2PkyFdkFN-2FNVPvV-2FeR4fkC7bh-2B1Wd-2FQfdxsHIWAa79-2BA5VBr-2BWRZYgyMmwm0QhsOpVUtFGxTnL-2Flw-3D-3D>
   and travel grant application
   
<http://links.c-in.eu/ls/click?upn=T7eHPghXgHXChvPFXj9jF1tnKdZ-2FbOF-2B7oR7I2RmVJnHrquLzIMjrtZNAAV0-2FQVF-2BzjoPh69-2Baf9gOawZKnHVw-3D-3DBYtB_R5xmhT1hyWYuWxjEu6rnxE8ohXQ2KDT5l1G-2FSzJNS5tjv-2B5JWZ2dTXhUrJuZAGSvYjmMydCLPvzAeuXqMLN0QExfCaIwPgVU69qcDiys46-2B1drvInonN0X1Z19oggXEazQ67lerKoEgb5tEkbQp9JdZ1AqmoMI3U2oK5AZuO3e-2FI0f2NWnOwAVLF0DFh2TBcK6yqkYbgXdGaAYsNJZPebQ-3D-3D>
   are open until 14 February 2023, 23:59 ET


M07 Earth System Response to Solar Radiation Modification: Modeling,
Impacts and Uncertainties*Convener(s): Govindasamy Bala (India), Hauke
Schmidt (Germany)*

*Co-Convener(s): Long Cao (China), Simone Tilmes (Spain), John Moore (USA),
Michael MacCracken (UK)*

*Description*
To achieve temperature stabilization goals set by the Paris Agreement
requires substantial reduction in greenhouse emissions and even net
negative CO2 emissions, which is a grand challenge for the human society.
Solar radiation modification (SRM), a class of climate intervention options
that aims to cool the Earth by deflecting some more sunlight back to space,
has attracted growing interest. Enhancement of the burden of reflective
aerosols in the stratosphere, increasing the reflectivity of marine clouds
by injecting cloud condensation nuclei and painting the urban roofs white
are some examples. SRM research is still at an early stage, in particular
with regard to efficiency, impacts and uncertainties of the different
proposals. This session welcomes contributions to all aspects of SRM
research, including modeling study of climate and Earth system response to
various forms of SRM, benefits and side effects of different SRM approaches
from local to global scales, and uncertainties underlying climate
processes, geophysical response and ecosystem and societal impact of SRM.
We also welcome studies on the engineering aspects of different SRM schemes
and international governance of SRM.


-- 
With Best Wishes,

---
G. Bala
Professor
Center for Atmospheric and Oceanic Sciences
Indian Institute of Science
Bangalore - 560 012
India

Tel: +91 80 2293 3428; +91 80 2293 2505
Fax: +91 80 2360 0865; +91 80 2293 3425
Email: gb...@iisc.ac.in; bala@gmail.com
Google Scholar <https://scholar.google.com/citations?user=eurjQPwJ>
---

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Re: [geo] Make sunsets - Calculating Cooling

[Govindasamy Bala]

this is all good and well-known, but the cost of this commercial venture
(as per the news) is way too high.

For a 2deg offset, the calculations show ~4 TgSO2 of injection per year
which translates to ~ 40 Trillion dollars per year at a rate of $10 per
gram of SO2. Cost estimates have gone through the roof into the
stratosphere from a few billion dollars to trillions of dollars. Well,
looks this is what commercialization would do. At this rate, the cost of
stratospheric aerosol geoengineering could be similar to the cost of
mitigation

Bala

On Wed, Dec 28, 2022 at 5:07 AM Andrew Lockley 
wrote:

> https://makesunsets.com/blogs/news/calculating-cooling
>
>
> DECEMBER 27, 2022
> Share
> Calculating Cooling
>
> How do we know how much cooling we're creating with our "clouds," and how
> does this compare to warming from carbon dioxide emissions?
> Fortunately, much smarter people have studied this for decades. Let's
> review some of their work and calculate our climate cooling impact.
>
> Radiative Forcing?
>
> Radiative forcing is the key concept here. This is how much energy enters
> the atmosphere vs. leaves it. An increase in radiative forcing leads to
> warming, and a decrease causes cooling. Here's a more detailed explanation.
> Measured in watts per square meter (W/m^2), we're over 3.1 W/m^2 of
> increased radiative forcing since 1750.
>
>
> Reflective Clouds
>
> How much reflectivity can we get from our clouds? Here's the summary we're
> working from:
>
>
>
> This number isn't pulled from thin air. As the author explains: "This
> sulfate efficacy value differs from that used in Smith and Wagner (2018)
> (which considered only incoming radiation) and falls towards the center of
> the values present across recent literature (Ferraro et al 2012, Pope et al
> 2012, Kuebbeler et al 2012, Pitari et al 2014, Kleinschmitt et al 2017, Dai
> et al 2018)."
>
> The key number here:
> -.62 W/m2 radiative forcing created for a year by injecting 1 Tg of sulfur
>
> But, we're using SO2. So, SO2/S mass ratio means we get half as much
> cooling per Tg:
> -.62/2 = -.31 W/m2 radiative forcing per Tg SO2/year
>
> CO2's Warming
>
> How much does carbon dioxide warm the planet? I was surprised about the
> uncertainty band here. IPCC says between .27 and .63 C per 1000 gigatons
> co2:
>
>
>
> So: 1000 gigatons CO2 = +.45C
>
> Converting Units
>
> Now we've got all the information we need to do our math. First, a
> conversion: temperature to radiative forcing. From the first table above,
> .7C per W/m2
>
> So, we'll convert our radiative forcing per Tg SO2 to temperature change:
> -.31 W/m2 * .7C per w/m2 = -.217 C per Tg SO2/year
>
> Residence Time
>
> How long do these particles create cooling? 1-3 years. For our purposes,
> we'll go with 2.1 years (although further particle optimization, higher
> injection altitudes, and other changes may eventually result in much
> greater residence time).
>
> So, 2.1 years particle life * -.217C per TG SO2/year = -.4557 C per Tg SO2
> launched for 1 year
>
> Putting It All Together
>
> So, how many grams of "cloud" to offset 1 ton of co2's warming impact for
> a year?
> 1000 gigatons co2 = +.45C
> 1 Tg SO2 = -.4557C
> 1000 gigatons co2 ~ 1 Tg SO2
> 1 gigaton = 1,000 Tg, so:
> 1,000*1,000 = 1,000,000 Tg co2 = 1 Tg SO2
> dividing both sides by 1T:
> 1,000,000 g co2 = 1 g SO2
> 1 metric ton = 1,000,000 g:
> 1 metric ton co2 = 1 g SO2
>
> So, with uncertainty bands on all of this, a gram offsets a ton: one gram
> "cloud" offsets 1 ton of co2's warming impact for a year.
>
> Here's the spreadsheet I used to calculate this, with links to sources.
>
> There are arguments to compare this in different ways (joules, etc.); many
> of these have strong merits. Because buyers of voluntary carbon credits are
> focused on co2 equivalence, we've gone this route.
>
> As with all our work here, please let us know if you think we've made a
> mistake and we'll correct!
>
> (image via Lexica)
>
>
> --
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> To unsubscribe from this group and stop receiving emails from it, send an
> email to geoengineering+unsubscr...@googlegroups.com.
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> 
> .
>


-- 
With Best Wishes,

---
G. Bala
Professor
Center for Atmospheric and Oceanic Sciences
Indian Institute of Science
Bangalore - 560 012
India

Tel: +91 80 2293 3428; +91 80 2293 2505
Fax: +91 80 2360 0865; +91 80 2293 3425
Email: gb...@iisc.ac.in; bala@gmail.com
Google Scholar 

Re: [geo] Make sunsets - Calculating Cooling

[Govindasamy Bala]

The $10 per gram for  "cooling credit" is mentioned in the original MIT
technology review news

On Wed, 28 Dec 2022, 15:52 Reiss Jones,  wrote:

> Thanks both for sharing these calculations on this.
>
> Bala, where did you get your $10 per gram number from? That would be
> $1,000,000 per tonne of SO2, when in reality it costs on average $9,000
> per tonne of SO2 <https://www.pharmacompass.com/price/sulfur-dioxide> -
> 99.1% cheaper. Using this figure it would only cost $36 billion per year.
>
> Best,
> Reiss
>
> *Reiss Jones*
> *Climate + Engineering + Synbio*
> *Inventions* <https://www.synthetic-rabbit.com>* Linkedin
> <https://www.linkedin.com/in/reiss-jones-b78520174/> **Blog*
> <https://reissjones.substack.com/?utm_source=substack&utm_medium=web&utm_campaign=substack_profile>
>
> On 28 Dec 2022, at 06:42, Govindasamy Bala  wrote:
>
> this is all good and well-known, but the cost of this commercial venture
> (as per the news) is way too high.
>
> For a 2deg offset, the calculations show ~4 TgSO2 of injection per year
> which translates to ~ 40 Trillion dollars per year at a rate of $10 per
> gram of SO2. Cost estimates have gone through the roof into the
> stratosphere from a few billion dollars to trillions of dollars. Well,
> looks this is what commercialization would do. At this rate, the cost of
> stratospheric aerosol geoengineering could be similar to the cost of
> mitigation
>
> Bala
>
> On Wed, Dec 28, 2022 at 5:07 AM Andrew Lockley 
> wrote:
>
>> https://makesunsets.com/blogs/news/calculating-cooling
>>
>>
>> DECEMBER 27, 2022
>> Share
>> Calculating Cooling
>>
>> How do we know how much cooling we're creating with our "clouds," and how
>> does this compare to warming from carbon dioxide emissions?
>> Fortunately, much smarter people have studied this for decades. Let's
>> review some of their work and calculate our climate cooling impact.
>>
>> Radiative Forcing?
>>
>> Radiative forcing is the key concept here. This is how much energy enters
>> the atmosphere vs. leaves it. An increase in radiative forcing leads to
>> warming, and a decrease causes cooling. Here's a more detailed explanation.
>> Measured in watts per square meter (W/m^2), we're over 3.1 W/m^2 of
>> increased radiative forcing since 1750.
>>
>>
>> Reflective Clouds
>>
>> How much reflectivity can we get from our clouds? Here's the summary
>> we're working from:
>>
>>
>>
>> This number isn't pulled from thin air. As the author explains: "This
>> sulfate efficacy value differs from that used in Smith and Wagner (2018)
>> (which considered only incoming radiation) and falls towards the center of
>> the values present across recent literature (Ferraro et al 2012, Pope et al
>> 2012, Kuebbeler et al 2012, Pitari et al 2014, Kleinschmitt et al 2017, Dai
>> et al 2018)."
>>
>> The key number here:
>> -.62 W/m2 radiative forcing created for a year by injecting 1 Tg of sulfur
>>
>> But, we're using SO2. So, SO2/S mass ratio means we get half as much
>> cooling per Tg:
>> -.62/2 = -.31 W/m2 radiative forcing per Tg SO2/year
>>
>> CO2's Warming
>>
>> How much does carbon dioxide warm the planet? I was surprised about the
>> uncertainty band here. IPCC says between .27 and .63 C per 1000 gigatons
>> co2:
>>
>>
>>
>> So: 1000 gigatons CO2 = +.45C
>>
>> Converting Units
>>
>> Now we've got all the information we need to do our math. First, a
>> conversion: temperature to radiative forcing. From the first table above,
>> .7C per W/m2
>>
>> So, we'll convert our radiative forcing per Tg SO2 to temperature change:
>> -.31 W/m2 * .7C per w/m2 = -.217 C per Tg SO2/year
>>
>> Residence Time
>>
>> How long do these particles create cooling? 1-3 years. For our purposes,
>> we'll go with 2.1 years (although further particle optimization, higher
>> injection altitudes, and other changes may eventually result in much
>> greater residence time).
>>
>> So, 2.1 years particle life * -.217C per TG SO2/year = -.4557 C per Tg
>> SO2 launched for 1 year
>>
>> Putting It All Together
>>
>> So, how many grams of "cloud" to offset 1 ton of co2's warming impact for
>> a year?
>> 1000 gigatons co2 = +.45C
>> 1 Tg SO2 = -.4557C
>> 1000 gigatons co2 ~ 1 Tg SO2
>> 1 gigaton = 1,000 Tg, so:
>> 1,000*1,000 = 1,000,000 Tg co2 = 1 Tg SO2
>> dividing 

[geo] Feedbacks for Solar vs CO2 forcing

[Govindasamy Bala]

This new paper from the Journal of Climate is relevant to solar
geoengineering.

Key take-home message: feedback strength is weaker for solar forcing than
CO2 forcing. This is related to the difference in latitudinal warming
patterns (solar forcing causes marginally larger warming in the tropical
regions and less warming in the polar regions)

https://journals.ametsoc.org/view/journals/clim/36/3/JCLI-D-21-0980.1.xml


ABSTRACT: Previous studies have shown that climate sensitivity, defined as
the global mean surface temperature change per unit radiative forcing, is
smaller for solar radiative forcing compared to an equivalent CO2 radiative
forcing.We investigate the causes for this difference using the NCAR CAM4
model. The contributions to the climate feedback parameter, which is
inversely related to climate sensitivity, are estimated for water vapor,
lapse rate, Planck, albedo, and cloud feedbacks using the radiative kernel
technique. The total feedback estimated for CO2 and solar radiative forcing
from our model simulations is 21.23 and 21.45 W m22 K21, respectively. We
find that the difference in feedback between the two cases is primarily due
to differences in lapse rate, water vapor, and cloud feedbacks, which
together explain 65%of the
difference in total feedback. The rest comes from Planck and albedo
feedbacks. The differences in feedbacks arise mainly from differences in
the horizontal (meridional) structure of forcing and the consequent
warming. Our study provides important insights into the effects of the
meridional structure of forcing on climate feedback, which is important for
evaluating global climate change from different forcing agents.


SIGNIFICANCE STATEMENT: An increase in atmospheric CO2 concentration or an
increase in incoming solar radiation leads to a rise in the radiative
budget and consequent climate warming, which is amplified by the presence of
multiple climate feedbacks. These feedbacks, from changes in surface
albedo, combined effect of water vapor and the vertical lapse rate of
temperature, and changes in clouds, differ between solar and CO2 forcing.
Using radiative kernels, this study quantifies these individual feedbacks
for an equivalent radiative change caused by an increase in CO2 or incoming
solar radiation, showing how the differences arise from differences in the
meridional patterns of warming. In agreement with prior studies, these
differences can explain the smaller efficacy of solar forcing compared to
CO2 forcing.

-- 
With Best Wishes,

---
G. Bala
Professor
Center for Atmospheric and Oceanic Sciences
Indian Institute of Science
Bangalore - 560 012
India

Tel: +91 80 2293 3428; +91 80 2293 2505
Fax: +91 80 2360 0865; +91 80 2293 3425
Email: gb...@iisc.ac.in; bala@gmail.com
Google Scholar 
---

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[geo] Fwd: IUGG 2023 - Important Updates for Conveners and Co-Conveners

[Govindasamy Bala]

A gentle reminder.
The abstract submission deadline for the IUGG session on SRM in Berlin is
14 Feb 2023

M07 Earth System Response to Solar Radiation Modification: Modeling,
Impacts and Uncertainties*Convener(s): Govindasamy Bala (India), Hauke
Schmidt (Germany)*

*Co-Convener(s): Long Cao (China), Simone Tilmes (USA), John Moore (China,
Finland), Michael MacCracken (USA)*



*DescriptionTo achieve temperature stabilization goals set by the Paris
Agreement requires substantial reduction in greenhouse emissions and even
net negative CO2 emissions, which is a grand challenge for the human
society. Solar radiation modification (SRM), a class of climate
intervention options that aims to cool the Earth by deflecting some more
sunlight back to space, has attracted growing interest. Enhancement of the
burden of reflective aerosols in the stratosphere, increasing the
reflectivity of marine clouds by injecting cloud condensation nuclei and
painting the urban roofs white are some examples. SRM research is still at
an early stage, in particular with regard to efficiency, impacts and
uncertainties of the different proposals. This session welcomes
contributions to all aspects of SRM research, including modeling study of
climate and Earth system response to various forms of SRM, benefits and
side effects of different SRM approaches from local to global scales, and
uncertainties underlying climate processes, geophysical response and
ecosystem and societal impact of SRM. We also welcome studies on the
engineering aspects of different SRM schemes and international governance
of SRM.*


-- Forwarded message -
From: 
Date: Wed, Jan 25, 2023 at 8:39 PM
Subject: IUGG 2023 - Important Updates for Conveners and Co-Conveners
To: 


[image: A picture containing text Description automatically generated]



Dear Govindasamy Bala,

We are contacting you to provide you with important updates and information
regarding your role as a convener/co-convener for the upcoming IUGG General
Assembly.

➤ Abstract submission
<http://links.c-in.eu/ls/click?upn=T7eHPghXgHXChvPFXj9jF1tnKdZ-2FbOF-2B7oR7I2RmVJnZKYoUQIYRgPcYd16aLLzxPZdu9OWUuR7d3wvtWSf0lQ-3D-3DTSor_R5xmhT1hyWYuWxjEu6rnxE8ohXQ2KDT5l1G-2FSzJNS5uVI3bFSriQg8A0mF94scz7yiN1CJ2Q2Opcdm3EenMf1kyRLF5az7nahQDONH7TB6PA-2FQkG4B9mSpS-2FqwJfmyYK8UQjYwGmsEvKowtpJpuaTfgHQbmq2Z59JcFAcu6UuAMJIs4N8NKLkXTMyFBDa8p8zgV6HEyP8COJ0UggAxWNFw-3D-3D>
and travel grant application
<http://links.c-in.eu/ls/click?upn=T7eHPghXgHXChvPFXj9jF1tnKdZ-2FbOF-2B7oR7I2RmVJnHrquLzIMjrtZNAAV0-2FQVF-2BzjoPh69-2Baf9gOawZKnHVw-3D-3DLSnt_R5xmhT1hyWYuWxjEu6rnxE8ohXQ2KDT5l1G-2FSzJNS5uVI3bFSriQg8A0mF94scz7rbpP9rGG2JvzsNFwRqCYt2tM8zGUupR0sZ1JAtjKq9LoeBcfxW6ILVIeijzeYJk4CLOm2TSw6KvIYC3ywaO0R97iw6GsPKdM6QwBiHMxKY7IcfjnGobGk1ao91sXltnX1TBjpHYT1eiElAJUEyYSmg-3D-3D>
are open until 14 February 2023, 23:59 ET

   - Please ensure to inform your solicited speakers that they need to
   submit their abstract(s) by this deadline as well.
   - Reports on abstract submission are available in the IUGG 2023 Portal
   
<http://links.c-in.eu/ls/click?upn=T7eHPghXgHXChvPFXj9jF2yoGsULnIwH-2FWNYq12IZkTPi1Dn1nKg2J-2BcZc7eFUWVAa9VykZZ0shzk8L9z74HwNFTP2fmFpXGXnmRYO5axDU-3Ds1l9_R5xmhT1hyWYuWxjEu6rnxE8ohXQ2KDT5l1G-2FSzJNS5uVI3bFSriQg8A0mF94scz7FEvdOMHLGM-2FaW3laGjuMHLdpLoguP78oKJeS0fBwaPuFq57ypEX3u8eWWalHFyoWeloWOq0X8SA444Wqm-2Fb5OVCE-2B20hCph9c1dzgAlQZGHwIthr6qGVG0EPjjWQAQ8QP3K8o8HtNWlFbps8HJFSHQ-3D-3D>.


➤ In order to receive as many abstracts as possible we appreciate your help
in promoting your session through your channels (e.g. mailing lists of your
university or research center).

   - IUGG promo materials and graphics can be downloaded here
   
<http://links.c-in.eu/ls/click?upn=T7eHPghXgHXChvPFXj9jF8vP1TpWBMLGxo9ycTODyZzCkYk8pwOr5VioMwxZti4ki-2BzbMrck526-2FqLQoIx2q7ciwyAyZ2-2Fk-2FxKPvPnPBWN8H9c-2FboJjVz3GRAZsIyrOl8Ds14idYKBAvCDDpgIAWOA-3D-3DbFA6_R5xmhT1hyWYuWxjEu6rnxE8ohXQ2KDT5l1G-2FSzJNS5uVI3bFSriQg8A0mF94scz7YT0hvhfDAejLVYFGbj7-2FfJpjLTdlvFo9D-2FNffSCHSx7CUGXERZtqV6QsDicnN5vONbchuKIw2aW69QQavUN9fTaD6wutvcPUKrp26wKx6uvR4ecC4lswvbn6vH82bIsebjN5AYWbtOMHER73fttI9g-3D-3D>.


➤ Solicited speakers can also be added to the description of your symposium
on the website. To do so, please send the solicited speakers’ names
(preferably also with their institute and country) to
kristyna.slavick...@c-in.eu or abstra...@iugg2023berlin.org.

➤ The program at glance, the associations and union schedule, and union
lecturers’ schedule are available on the website
<http://links.c-in.eu/ls/click?upn=T7eHPghXgHXChvPFXj9jF1tnKdZ-2FbOF-2B7oR7I2RmVJnUnECH07wI5Isgt7KIVzFDSEO3q19IxpKT5U-2FFP0B8XA-3D-3D-Oke_R5xmhT1hyWYuWxjEu6rnxE8ohXQ2KDT5l1G-2FSzJNS5uVI3bFSriQg8A0mF94scz7jhZ8n6ooBXZUvyIRmWUEN7cg5g3AUgwLIVNtUd-2F6Np3lKQEDnIHeHTYbDqlU9A63mOEOw5Stj-2FSVaht8TO9-2B1-2FWRIQb2fyJK2XJZade7zU2xW1QIvd516tqAqIuC9JwVhL71QQIhb6BXmyLNpC8rEg-3D-3D>.


➤ All important information for conveners and co-conveners was sent by
e-mail and is also a

[geo] IUGG meeting

[Govindasamy Bala]

A gentle reminder.

The abstract submission deadline for the IUGG session on SRM in Berlin is
14 Feb 2023

M07 Earth System Response to Solar Radiation Modification: Modeling,
Impacts and Uncertainties*Convener(s): Govindasamy Bala (India), Hauke
Schmidt (Germany)*

*Co-Convener(s): Long Cao (China), Simone Tilmes (USA), John Moore (China,
Finland), Michael MacCracken (USA)*


*DescriptionTo achieve temperature stabilization goals set by the Paris
Agreement requires substantial reduction in greenhouse emissions and even
net negative CO2 emissions, which is a grand challenge for the human
society. Solar radiation modification (SRM), a class of climate
intervention options that aims to cool the Earth by deflecting some more
sunlight back to space, has attracted growing interest. Enhancement of the
burden of reflective aerosols in the stratosphere, increasing the
reflectivity of marine clouds by injecting cloud condensation nuclei and
painting the urban roofs white are some examples. SRM research is still at
an early stage, in particular with regard to efficiency, impacts and
uncertainties of the different proposals. This session welcomes
contributions to all aspects of SRM research, including modeling study of
climate and Earth system response to various forms of SRM, benefits and
side effects of different SRM approaches from local to global scales, and
uncertainties underlying climate processes, geophysical response and
ecosystem and societal impact of SRM. We also welcome studies on the
engineering aspects of different SRM schemes and international governance
of SRM.*

-- 
With Best Wishes,

---
G. Bala
Professor
Center for Atmospheric and Oceanic Sciences
Indian Institute of Science
Bangalore - 560 012
India

Tel: +91 80 2293 3428; +91 80 2293 2505
Fax: +91 80 2360 0865; +91 80 2293 3425
Email: gb...@iisc.ac.in; bala@gmail.com
Google Scholar <https://scholar.google.com/citations?user=eurjQPwJ>
---

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[geo] Fwd: IUGG 2023 - Abstract Submission Deadline EXTENDED

[Govindasamy Bala]

-- Forwarded message -
From: 
Date: Mon, Feb 13, 2023 at 8:41 PM
Subject: IUGG 2023 - Abstract Submission Deadline EXTENDED
To: 


[image: A picture containing text Description automatically generated]



Dear Govindasamy Bala,

This is to kindly inform you that the abstract submission and travel grant
application deadline has been extended to:

21 February 2023, 23:59 Pacific Time

Please make sure to distribute this information through any channels
available to you.

Link to a mailing with this information:
https://iugg2023.ecomailapp.cz/public/show/2096/3/f1bcbbd02ef1ec55c93baff1863d4cf8

➤ REPORTING is available in the IUGG 2023 Portal
<http://links.c-in.eu/ls/click?upn=T7eHPghXgHXChvPFXj9jF2yoGsULnIwH-2FWNYq12IZkTPi1Dn1nKg2J-2BcZc7eFUWVAa9VykZZ0shzk8L9z74HwNFTP2fmFpXGXnmRYO5axDU-3D9xb9_R5xmhT1hyWYuWxjEu6rnxE8ohXQ2KDT5l1G-2FSzJNS5vYSSxpr9Ogqr3ZveqNSaEcnotppBrid-2BsJYapeh42A6Ky23dxWURvQ-2BbWZZJBu4ohbxjtxEcFjuTn98-2Ftx16MVjRpyD33j29ObxzSb-2F4eVuU0L6alj2HYvZBzT9Lvq36kyp9-2B9KpetBFSOTAF-2FPuKhOF53bcNF09RQIOx7UCBbmw-3D-3D>
(bottom of the page), or

➢ Detailed report with author names, abstract title and text + statistics
available HERE
<http://links.c-in.eu/ls/click?upn=T7eHPghXgHXChvPFXj9jF6j1kDAzKPSz2Toa2eHJfqCM6sAtyDStUq21Nj3AvdHtJpIBFLs4FF4CcI-2BbBPkTen0h-2B6bPfyWSVinIqbzBsnZGnnt25iM3LmcXpTUROtxXGY3XXOXxAzjsTZAy-2BWczfoQdf6Aw3M2DHkgwi9kFERmXZsDXRROuvkYtzHQy8b5Zw5HD_R5xmhT1hyWYuWxjEu6rnxE8ohXQ2KDT5l1G-2FSzJNS5vYSSxpr9Ogqr3ZveqNSaEcK3cORkEaspBW3DFp3vRlTQt6UYQMOL8MqJZ51-2B9gtnSSFRvldK3Ni0cErgHqq39JjjSFXr01wcxBbivnXRWE-2B5R04nwV9UM4Hvt9SE24Vhrlco-2BaROlAsAvQXH3bpm07zdoblS-2Frkck4mrWMoFJYMw-3D-3D>
(updated daily)

➢ Report on the number of abstracts submitted to your symposium is
available HERE
<http://links.c-in.eu/ls/click?upn=T7eHPghXgHXChvPFXj9jF2yoGsULnIwH-2FWNYq12IZkTfFA3BHEhE2fMH59stqPbvir0sN3Mji-2BgFwmYPYnILkYQNpkIS8Z8ZIok89jIRqI8dqYIULrsZA8RqUY6cg9QE4rNByE6nZrz7AWExRc-2BMmx73qTd9gND-2BBoJpyMW4idxdWZopmakiCU8qcHudJT83zAX1_R5xmhT1hyWYuWxjEu6rnxE8ohXQ2KDT5l1G-2FSzJNS5vYSSxpr9Ogqr3ZveqNSaEcJ636j4dc6IcHfoiKlD57IEojUcDzW3WDRh4-2FpsNdE2GFhAGFat2RDiVqvOiK-2FIFDg-2B-2B-2FnncSpIHoUMOSBzy4zFN69OD-2BnlCPTbCSsUNHHWq4-2BwVtmpEu-2B0GwIiEeS-2FGnhzws0KONN1yV29A6IEl3MQ-3D-3D>
(updated hourly)

➤ PROMOTION of your symposium is highly appreciated and encouraged.

➢ IUGG promo materials and graphics can be downloaded here
<http://links.c-in.eu/ls/click?upn=T7eHPghXgHXChvPFXj9jF8vP1TpWBMLGxo9ycTODyZzCkYk8pwOr5VioMwxZti4ki-2BzbMrck526-2FqLQoIx2q7ciwyAyZ2-2Fk-2FxKPvPnPBWN8H9c-2FboJjVz3GRAZsIyrOl8Ds14idYKBAvCDDpgIAWOA-3D-3DbhmB_R5xmhT1hyWYuWxjEu6rnxE8ohXQ2KDT5l1G-2FSzJNS5vYSSxpr9Ogqr3ZveqNSaEcWERoGaisPMMrMcvE8Ql1E-2B2XpeW-2Br1Xvh7R7ttyxFqZb2RTE7ciJ0BjZesZXmKuzyZQObegtMWipSl7QoZjTEeTxM-2ByjmrQ1SjiFVh7yP3fhTreEQoZliJHF0ssvtVQh5NzQAOmTguFjvGaRzFBxWw-3D-3D>.


➤ SOLICITED SPEAKERS

➢ Need to submit their abstract(s) by 21 February as well. Use the detailed
report
<http://links.c-in.eu/ls/click?upn=T7eHPghXgHXChvPFXj9jF6j1kDAzKPSz2Toa2eHJfqCM6sAtyDStUq21Nj3AvdHtJpIBFLs4FF4CcI-2BbBPkTen0h-2B6bPfyWSVinIqbzBsnZGnnt25iM3LmcXpTUROtxXGY3XXOXxAzjsTZAy-2BWczfoQdf6Aw3M2DHkgwi9kFERmXZsDXRROuvkYtzHQy8b5ZI3Rf_R5xmhT1hyWYuWxjEu6rnxE8ohXQ2KDT5l1G-2FSzJNS5vYSSxpr9Ogqr3ZveqNSaEc8cG9oZQRFcYgTRQz3U6qOcetnN2m-2BnWFudH6Cnf6Pj-2F2ZAn7WZKH6ZDUDsfhCTpJCMHuFAKUve76vuxByz-2BY85aSV9G84NLsfj63R5y5NqGrptCkNKS-2Bh-2BSmtp86ggOKRtVDL2E5-2BYl5xp6SA8P30A-3D-3D>
to see who already submitted their abstract.

➢ Do not receive any financial support or fee waiver, but can apply for a
travel grant
<http://links.c-in.eu/ls/click?upn=T7eHPghXgHXChvPFXj9jF1tnKdZ-2FbOF-2B7oR7I2RmVJnHrquLzIMjrtZNAAV0-2FQVF-2BzjoPh69-2Baf9gOawZKnHVw-3D-3DKCVm_R5xmhT1hyWYuWxjEu6rnxE8ohXQ2KDT5l1G-2FSzJNS5vYSSxpr9Ogqr3ZveqNSaEcVwjPAPthuhoKsMXKtsNqZu722D2PkR08kJAU36GrwB-2FX-2B2GMT1x9Th9-2B2KiGewi-2F31r-2BP8KjQfV2S4M4sjII5LjvRQ4ERsbIdkimRD237XgPDFHdhRAsXy4CmhuMxAA98mcySZz3yqXyRsMBsPhxkQ-3D-3D>
.

➢ Normally receive 30 minutes for their presentation, while "standard"
speakers receive 15 minutes. But conveners can change that for their
symposium's session if necessary. The number of solicited speakers is not
limited.

➢ Can also be added to the description of your symposium on the website. To
do so, please send the solicited speakers’ names, institute and country) to
kristyna.slavick...@c-in.eu or abstra...@iugg2023berlin.org.

We would like to thank you in advance for your kind cooperation.

Should you have any questions or requests, please do not hesitate to
contact us.



Kind regards,

IUGG 2023 Scientific Program Secretariat



-- 
With Best Wishes,

---
G. Bala
Professor
Center for Atmospheric and Oceanic Sciences
Indian Institute of Science
Bangalore - 560 012
India

Tel: +91 80 2293 3428; +91 80 2293 2505
Fax: +91 80 2360 0865; +91 80 2293 3425
Email: gb...@iisc.ac.in; bala@gmail.com
Google Scholar <

Re: [geo] positive forcing in all SSPs but GMST falls ?

[Govindasamy Bala]

It is all "relative". The 1.9 Wm-2 is relative to the pre-industrial times
and hence there is a warming in 2100 relative to the preindustrial time.

However, in the SSP1-1.9 scenario, the forcing and warming peak somewhere
around 2050, and then the forcing (and hence warming) decline slightly
because of net negative emissions after 2050. Yes, there is slight cooling
in 2100 relative to 2050..

Cheers,
Bala

On Tue, Mar 28, 2023 at 9:14 PM Colin Forrest 
wrote:

> Hi,  could someone perhaps explain why the SSP 1.9 for example has a
> climate forcing of 1.9 W.m-2 at 2100, yet is modelled to produce a
> reduction in GMST ?
>
> Considering that current net anthropogenic forcing is 2.72 W.m-2 (AR6, WG
> 1, full report, ch 7 page 926 )
>
> Thanks,  Colin Forrest
>
> --
> You received this message because you are subscribed to the Google Groups
> "geoengineering" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to geoengineering+unsubscr...@googlegroups.com.
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> 
> .
>


-- 
With Best Wishes,

---
G. Bala
Professor
Center for Atmospheric and Oceanic Sciences
Indian Institute of Science
Bangalore - 560 012
India

Tel: +91 80 2293 3428; +91 80 2293 2505
Fax: +91 80 2360 0865; +91 80 2293 3425
Email: gb...@iisc.ac.in; bala@gmail.com
Google Scholar 
---

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[geo] Aerosol loading and tropical monsoon precipitation

[Govindasamy Bala]

https://link.springer.com/article/10.1007/s00382-023-06799-3

This new paper in Climate Dynamics is relevant to stratospheric sulfate
aerosol geoengineering.
The interhemispheric difference in forcing causes a sure signal in tropical
monsoon systems. Some of you may be already well aware of this. In this new
paper, we quantified this sensitivity for stratospheric sulfate aerosol
loading. The northern hemispheric monsoon index changes by ~7% per 0.1
change in the AOD difference between the hemispheres and ~ 6% per 1 K
change in temperature difference between the hemispheres.

With Best Wishes,

---
G. Bala
Professor
Center for Atmospheric and Oceanic Sciences
Indian Institute of Science
Bangalore - 560 012
India

Tel: +91 80 2293 3428; +91 80 2293 2505
Fax: +91 80 2360 0865; +91 80 2293 3425
Email: gb...@iisc.ac.in; bala@gmail.com
Google Scholar 
---

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[geo] Safe and Just Earth System Boundaries

[Govindasamy Bala]

Not sure if this Nature paper was posted last week.

https://doi.org/10.1038/s41586-023-06083-8

The metric for safe aerosol loading for the global boundary is the
interhemispheric differences in AOD. The setting of this global boundary
was partly inferred from several previous SAG (stratospheric aerosol
geoengineering) modeling studies.

Abstract
The stability and resilience of the Earth system and human well-being are
inseparably linked1
,2
,3
, yet their
interdependencies are generally under-recognized; consequently, they are
often treated independently4
,5
. Here, we use
modelling and literature assessment to quantify safe and just Earth system
boundaries (ESBs) for climate, the biosphere, water and nutrient cycles,
and aerosols at global and subglobal scales. We propose ESBs for
maintaining the resilience and stability of the Earth system (safe ESBs)
and minimizing exposure to significant harm to humans from Earth system
change (a necessary but not sufficient condition for justice)4
. The stricter
of the safe or just boundaries sets the integrated safe and just ESB. Our
findings show that justice considerations constrain the integrated ESBs
more than safety considerations for climate and atmospheric aerosol
loading. Seven of eight globally quantified safe and just ESBs and at least
two regional safe and just ESBs in over half of global land area are
already exceeded. We propose that our assessment provides a quantitative
foundation for safeguarding the global commons for all people now and into
the future.

-- 
With Best Wishes,

---
G. Bala
Professor
Center for Atmospheric and Oceanic Sciences
Indian Institute of Science
Bangalore - 560 012
India

Tel: +91 80 2293 3428; +91 80 2293 2505
Fax: +91 80 2360 0865; +91 80 2293 3425
Email: gb...@iisc.ac.in; bala@gmail.com
Google Scholar 
---

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[geo] SRM and tropical Monsoon precipitation

[Govindasamy Bala]

https://academic.oup.com/oocc/article/4/1/kgae016/7737801

Here is a paper published in Oxford Open Climate Change last week. We show
that tropical summer MEAN monsoon precipitation CHANGES can be estimated
using just two parameters in the case of stratospheric aerosol
geoengineering: global mean aerosol optical depth (AOD) and
interhemispheric differences in AOD. It is a simple 2-parameter linear
model. Instead of AOD, radiative forcing or surface temperature could be
also used in this formulation which, I believe, provides a closure to the
estimation of tropical mean monsoon precipitation changes not just for SAI
but for any forcing.


An investigation of the relationship between tropical monsoon precipitation
changes and stratospheric sulfate aerosol optical depth
Anu Xavier, Govindasamy Bala, Shinto Roose, Usha KH


Abstract

Stratospheric aerosol geoengineering (SAG) is one of the several solar
geoengineering options that have been proposed to counteract climate
change. In the case of SAG, reflective aerosols injected into the
stratosphere would reflect more sunlight and cool the planet. When
assessing the potential efficacy and risks of SAG, the sensitivity of
tropical monsoon precipitation changes should be also considered. Using a
climate model, we perform several stylized simulations with different
meridional distributions and amounts of volcanic sulfate aerosols in the
stratosphere. Because tropical monsoon precipitation responds to global
mean and interhemispheric difference in radiative forcing or temperature,
we quantify the sensitivity of tropical monsoon precipitation to SAG in
terms of two parameters: global mean aerosol optical depth (GMAOD) and
interhemispheric AOD difference (IHAODD). For instance, we find that the
simulated northern hemisphere monsoon precipitation has a sensitivity of
−1.33 ± 0.95% per 0.1 increase in GMAOD and −7.62 ± 0.27% per 0.1 increase
in IHAODD. Our estimated precipitation changes in terms of the two
sensitivity parameters for the global mean precipitation and for the
indices of tropical, northern hemisphere, southern hemisphere and Indian
summer monsoon precipitation are in good agreement with the model simulated
precipitation changes. Similar sensitivity estimates are also made for unit
changes in global mean and interhemispheric differences in effective
radiative forcing and surface temperature. Our study based on planetary
energetics provides a simpler framework for understanding the tropical
monsoon precipitation response to external forcing agents.

-- 
With Best Wishes,

---
G. Bala
Professor
Center for Atmospheric and Oceanic Sciences
Indian Institute of Science
Bangalore - 560 012
India

Tel: +91 80 2293 3428; +91 80 2293 2505
Email: gb...@iisc.ac.in; bala@gmail.com
Google Scholar <https://scholar.google.com/citations?user=eurjQPwJ>
---

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