Re: [geo] Re: Stoat strongly criticises AMEG

[Andrew Lockley]

There was a good study at WCRP which showed that much of the inter annual
variability is wind related, as ice is moved towards the Atlantic in
certain years.

I don't know if It's in print yet.

Veli has made this point before, and the modelling seems to support his
view.

This is worrying, as It's a non thermal process. SRM can't predictably
change the wind, so unless we can rapidly rebuild the ice to a continuous
mass, it will tend to get blown away when the winds dictate.

A
On Mar 19, 2012 1:15 AM, "Mike MacCracken"  wrote:

>  Just to note, however, that we really do not have a good sense of how
> big or small variability can be at this melting trend continues—variability
> is very unlikely, in my view to be much of a saving influence on the
> decadal scale unless some strong cooling influence results—whether from a
> major volcanic eruption, lots more sulfate pollution on the global scale,
> or climate engineering. With world warming, it is hard to have the Arctic
> go very far or very long in the opposite direction.
>
> Mike MacCracken
>
>
>
>
> On 3/18/12 3:43 PM, "Andy Revkin"  wrote:
>
> I'm with Stoat, Ken Caldeira, David Keith, Alan Robock and others who see
> this "emergency" effort to rush cloud intervention in the Arctic on behalf
> of sea ice (and indirectly seabed methane) as undermining the case for a
> serious push on geo-engineering options, impacts and policy issues. You're
> getting headlines and the attention of factions in Parliament now, but just
> wait until the variability kicks the other way.
>
> "Yelling fire on a hot planet" <
> http://www.nytimes.com/2006/04/23/weekinreview/23revkin.html?_r=2>  can
> have unanticipated consequences.
>
>  --
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[geo] Re: Stoat strongly criticises AMEG

[Josh Horton]

I agree with Nathan that we shouldn't lose sight of the methane issue, 
which is the motive force behind AMEG's assertions and activities.  In this 
regard, here is a short excerpt from something I posted in December:
*
*
*While declaring a methane emergency and calling for immediate action is 
rooted in good intentions, such advocacy is both premature and misguided. 
In scientific terms, the available evidence simply does not support 
assertions that a worst-case scenario is unfolding. Shakhova and Semiletov 
have discovered an important phenomenon in the ESAS, but there are no data 
to indicate that this is a new phenomenon, or that methane venting is 
increasing at a statistically significant rate, or that venting is tightly 
connected to sea-ice retreat and the ice-albedo feedback. Arctic climate 
expert Ed Dlugokencky has written that "There is no evidence from our 
atmospheric measurements that there has been a significant increase in 
emissions during the past 20 years from natural methane sources in the 
Arctic so 
far."
 
Ice expert Richard Alley states "the physical understanding agrees with the 
paleoclimatic data that methane can be an important feedback but isn't 
likely to have giant rapid climate-changing 
belches."
 
Even Shakhova and Semiletov urge restraint: "we have never stated that the 
reason for the currently observed methane emissions were due to recent 
climate change. ... We would urge people ... not jump to conclusions and be 
open to the idea that new observations may significantly change what we 
understand about our 
world.
"*
*
*
*Demands for quick deployment are also politically unwise. Given the 
mainstream scientific views described above, such calls will not be heeded, 
but instead will be attributed to "the scientific 
fringe,"
 
which could in turn contribute to the marginalization of the broader 
geoengineering community. This would be especially tragic if compelling 
evidence subsequently emerges that we are indeed at an Arctic tipping 
point: climate remediation solutions may be dismissed as the 
science-fiction fantasies of doomsday prognosticators, even if the 
underlying engineering is sound and deployment warranted by an objective 
reading of events. Monitoring of Arctic methane venting should be 
increased, and research on global and regional geoengineering schemes 
should be intensified, but assertions that we are on the brink of calamity 
and must act now should cease. There is a difference between vigilance and 
alarmism, and the Arctic Methane Emergency Group is rapidly drifting toward 
the latter.*

(see here for the full post including links -- 
http://geoengineeringpolitics.blogspot.com/2011/12/arctic-methane-emergencies-and-alarmism.html)

I'm not aware of any subsequent developments that warrant revising these 
statements.  A close look at the methane issue gives us even more reason to 
question the claims put forward by AMEG, and perhaps for AMEG to reconsider 
its approach.

Josh Horton


On Sunday, March 18, 2012 7:59:29 AM UTC-4, Andrew Lockley wrote:
>
> This is very damning. I have also asked John several times to clarify the 
> membership of the group and he has not done so.  Bearing in mind the high 
> media profile of the AMEG group, the issue is a major threat to the public 
> credibility of the entire geoengineering research community.
>
> http://t.co/OZnj6dMM 
>
> Arctic Methane Emergency Group? Posted on: March 17, 2012 4:16 PM, by 
> William M. Connolley
>
> From Climate 'tech fixes' urged for Arctic methane I find ameg.me who say:
>
> AMEG POSITION DECLARATION OF EMERGENCY We declare there now exists an 
> extremely high international security risk* from abrupt and runaway global 
> warming being triggered by the end-summer collapse of Arctic sea ice 
> towards a fraction of the current record and release of huge quantities of 
> methane gas from the seabed. Such global warming would lead at first to 
> worldwide crop failures but ultimately and inexorably to the collapse of 
> civilization as we know it. This colossal threat demands an immediate 
> emergency scale response to cool the Arctic and save the sea ice. The 
> latest available data indicates that a sea ice collapse is more than likely 
> by 2015 and even possible this summer (2012). Thus some measures to counter 
> the threat have to be ready within a few months.
>
> So who are these bozos? (Note: I've been fairly dismissive about methane 
> before). Aunty says "Scientists told UK MPs this week... At a meeting in 
> Westminster organised by the Ar

Re: [geo] Re: Stoat strongly criticises AMEG

[Mike MacCracken]

True, but with Arctic warming and general reduction in sea ice and so in
cold air generated in Arctic, it is all related, so just projecting ahead
past levels and characteristics of variability is unlikely, in my view, to
be valid. Also, thermodynamically, it is quite hard to maintain a colder
Arctic as the world warms‹the Arctic is a small percentage of the area
(despite Mercator-based misimpressions)--and so what goes on elsewhere will
carry into the Arctic.

Mike


On 3/19/12 3:51 AM, "Andrew Lockley"  wrote:

> There was a good study at WCRP which showed that much of the inter annual
> variability is wind related, as ice is moved towards the Atlantic in certain
> years.
> 
> I don't know if It's in print yet.
> 
> Veli has made this point before, and the modelling seems to support his view.
> 
> This is worrying, as It's a non thermal process. SRM can't predictably change
> the wind, so unless we can rapidly rebuild the ice to a continuous mass, it
> will tend to get blown away when the winds dictate.
> 
> A 
> 
> On Mar 19, 2012 1:15 AM, "Mike MacCracken"  wrote:
>> Just to note, however, that we really do not have a good sense of how big or
>> small variability can be at this melting trend continues‹variability is very
>> unlikely, in my view to be much of a saving influence on the decadal scale
>> unless some strong cooling influence results‹whether from a major volcanic
>> eruption, lots more sulfate pollution on the global scale, or climate
>> engineering. With world warming, it is hard to have the Arctic go very far or
>> very long in the opposite direction.
>> 
>> Mike MacCracken
>> 
>> 
>> 
>> 
>> On 3/18/12 3:43 PM, "Andy Revkin" http://rev...@gmail.com>
>> > wrote:
>> 
>>> I'm with Stoat, Ken Caldeira, David Keith, Alan Robock and others who see
>>> this "emergency" effort to rush cloud intervention in the Arctic on behalf
>>> of sea ice (and indirectly seabed methane) as undermining the case for a
>>> serious push on geo-engineering options, impacts and policy issues. You're
>>> getting headlines and the attention of factions in Parliament now, but just
>>> wait until the variability kicks the other way.
>>> 
>>> "Yelling fire on a hot planet"
>>>   can
>>> have unanticipated consequences.

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Re: [geo] Source on SRM causing warming

[Alan Robock]

Dear Mike,

I don't know how you do this 6 to 1 calculation.  We found that the 
e-folding time for stratospheric aerosols in the Arctic s 2-4 months, 
with 4 months in the summer, the relevant time.  (see 
http://climate.envsci.rutgers.edu/pdf/2008JD010050small.pdf )  If we 
compare this to the lifetime of tropospheric aerosols, on week, and add 
a week to the 4 months for their tropospheric time, the ratio is 130 
days to 7 days, which is *19 to 1, not 6 to 1*.  Furthermore, the health 
effects of additional tropospheric pollution are not acceptable, in my 
opinion.



Alan

[On sabbatical for current academic year.  The best way to contact me
is by email, rob...@envsci.rutgers.edu, or at 732-881-1610 (cell).]

Alan Robock, Professor II (Distinguished Professor)
  Editor, Reviews of Geophysics
  Director, Meteorology Undergraduate Program
  Associate Director, Center for Environmental Prediction
Department of Environmental SciencesPhone: +1-732-932-9800 x6222
Rutgers University  Fax: +1-732-932-8644
14 College Farm Road   E-mail: rob...@envsci.rutgers.edu
New Brunswick, NJ 08901-8551  USA  http://envsci.rutgers.edu/~robock


On 3/18/2012 5:49 PM, Mike MacCracken wrote:

Hi Stephen--My wording must have been confusing.

For stratospheric injections at low latitudes, the lifetime is 1-2 years.
The aerosols do move poleward and are carried into the troposphere in mid
and high latitudes. This is one approach to trying to limit global climate
change, and, as David Keith says, studies indicate that these cool the polar
regions, though perhaps not in the stratosphere.

Your cloud brightening approach is also to limit global warming. I'd also
suggest that we could offset some of the global warming by sulfate aerosols
out over vast ocean areas instead of sulfate's present dominance over, now,
southeastern Asia, China, etc.--so keeping or modestly enhancing the present
cooling offset. [And reducing cirrus may also be a viable approach.]

A third approach is to cool the poles (and this might be good for regional
purposes alone), but cooling also pulls heat out of lower latitudes and
helps to cool them somewhat. The Caldeira-Wood shows it works conceptually
(they reduced solar constant) and Robock et al. injected SO2 into
stratosphere to do (but the full year injection of SO2/SO4 likely spread
some to lower latitudes and the monsoons were affected). One thing Robock et
al. found was that the lifetime of sulfate in the polar stratosphere is
about two months, and so that means that the potential 100 to 1 advantage of
stratospheric sulfate is not valid, and we're down to 6 to 1 compared to
surface-based approaches such as CCN or microbubbles to cool incoming
waters, sulfate or something similar over Arctic area, surface brightening
by microbubbles, etc.--noting that such approaches are only needed (and
effective) for the  few months per year when the Sun is well up in the sky.

As David Keith also says, there is a lot of research to be done to determine
which approaches or alone or in different variants might work, or be
effective or ineffective and have unintended consequences, much less how
such an approach or set of approaches might be integrated with mitigation,
adaptation, suffering, etc.

Best, Mike MacCracken






On 3/18/12 12:52 PM, "Stephen Salter"  wrote:


Mike

I had thought that the plan was stratospheric aerosol to be released at
low latitudes and would slowly migrate to the poles where is would
gracefully descend.  If you can be sure that it will all have gone in 10
days then my concerns vanish.  But if the air cannot get through the
water surface how can the aerosol it carries get there?  It will form a
blanket even if it is a very low one.

A short life would mean  that we do not have to worry about methane
release.  But can we do enough to cool the rest of the planet?  Perhaps
Jon Egil can tell us about blanket lifetime.

Stephen

Mike MacCracken wrote:

The Robock et al simulations of an Arctic injection found that the lifetime
of particles in the lower Arctic stratosphere was only two months. In that
one would only need particles up during the sunlit season (say three months,
for only really helps after the sea ice surface has melted and the sun is
high in the sky). During the relatively calm weather of Arctic summer, the
lifetime of tropospheric sulfate, for example

That is just misleading.  The third attachment is a top-of-atmosphere
radiation balance on the email I am responding to shows shortwave radiation.

The attached figure shows the corresponding temperature field from the same
simulation for the same time period.  Note Arctic cooling.

Also, we should not focus on individual regional blobs of color in an
average
of a single decade from a single simulation.

The paper these figures came from is here:
http://www.atmos-chem-phys.net/10/5999/2010/acp-10-5999-2010.pdf

___
Ken Caldeira

Carnegie Institution Dept of Glob

RE: [geo] Source on SRM causing warming - tropospheric health effects.

[John Latham]

Hello Alan,

Re tropospheric health effects:-

Are you talking exclusively about sulphur, or would you apply the
same argument to seawater droplets, as used in MCB?

Estimated global seawater volumetric dissemination rate to produce 
cooling to balance warming from 2xCO2 is about 10 m**3 / sec,
almost all of which would fall back into the oceans.

All Best, John.



John Latham
Address: P.O. Box 3000,MMM,NCAR,Boulder,CO 80307-3000
Email: lat...@ucar.edu  or john.latha...@manchester.ac.uk
Tel: (US-Work) 303-497-8182 or (US-Home) 303-444-2429
 or   (US-Cell)   303-882-0724  or (UK) 01928-730-002
http://www.mmm.ucar.edu/people/latham

From: geoengineering@googlegroups.com [geoengineering@googlegroups.com] on 
behalf of Alan Robock [rob...@envsci.rutgers.edu]
Sent: Monday, March 19, 2012 4:03 PM
To: mmacc...@comcast.net
Cc: Stephen Salter; Ken Caldeira; Andrew Lockley; Geoengineering; 
j.e.kristjans...@geo.uio.no
Subject: Re: [geo] Source on SRM causing warming

Dear Mike,

I don't know how you do this 6 to 1 calculation.  We found that the e-folding 
time for stratospheric aerosols in the Arctic s 2-4 months, with 4 months in 
the summer, the relevant time.  (see 
http://climate.envsci.rutgers.edu/pdf/2008JD010050small.pdf )  If we compare 
this to the lifetime of tropospheric aerosols, on week, and add a week to the 4 
months for their tropospheric time, the ratio is 130 days to 7 days, which is 
19 to 1, not 6 to 1.  Furthermore, the health effects of additional 
tropospheric pollution are not acceptable, in my opinion.


Alan

[On sabbatical for current academic year.  The best way to contact me
is by email, rob...@envsci.rutgers.edu, or at 
732-881-1610 (cell).]

Alan Robock, Professor II (Distinguished Professor)
  Editor, Reviews of Geophysics
  Director, Meteorology Undergraduate Program
  Associate Director, Center for Environmental Prediction
Department of Environmental SciencesPhone: +1-732-932-9800 x6222
Rutgers University  Fax: +1-732-932-8644
14 College Farm Road   E-mail: 
rob...@envsci.rutgers.edu
New Brunswick, NJ 08901-8551  USA  http://envsci.rutgers.edu/~robock


On 3/18/2012 5:49 PM, Mike MacCracken wrote:

Hi Stephen--My wording must have been confusing.

For stratospheric injections at low latitudes, the lifetime is 1-2 years.
The aerosols do move poleward and are carried into the troposphere in mid
and high latitudes. This is one approach to trying to limit global climate
change, and, as David Keith says, studies indicate that these cool the polar
regions, though perhaps not in the stratosphere.

Your cloud brightening approach is also to limit global warming. I'd also
suggest that we could offset some of the global warming by sulfate aerosols
out over vast ocean areas instead of sulfate's present dominance over, now,
southeastern Asia, China, etc.--so keeping or modestly enhancing the present
cooling offset. [And reducing cirrus may also be a viable approach.]

A third approach is to cool the poles (and this might be good for regional
purposes alone), but cooling also pulls heat out of lower latitudes and
helps to cool them somewhat. The Caldeira-Wood shows it works conceptually
(they reduced solar constant) and Robock et al. injected SO2 into
stratosphere to do (but the full year injection of SO2/SO4 likely spread
some to lower latitudes and the monsoons were affected). One thing Robock et
al. found was that the lifetime of sulfate in the polar stratosphere is
about two months, and so that means that the potential 100 to 1 advantage of
stratospheric sulfate is not valid, and we're down to 6 to 1 compared to
surface-based approaches such as CCN or microbubbles to cool incoming
waters, sulfate or something similar over Arctic area, surface brightening
by microbubbles, etc.--noting that such approaches are only needed (and
effective) for the  few months per year when the Sun is well up in the sky.

As David Keith also says, there is a lot of research to be done to determine
which approaches or alone or in different variants might work, or be
effective or ineffective and have unintended consequences, much less how
such an approach or set of approaches might be integrated with mitigation,
adaptation, suffering, etc.

Best, Mike MacCracken






On 3/18/12 12:52 PM, "Stephen Salter" 
 wrote:



Mike

I had thought that the plan was stratospheric aerosol to be released at
low latitudes and would slowly migrate to the poles where is would
gracefully descend.  If you can be sure that it will all have gone in 10
days then my concerns vanish.  But if the air cannot get through the
water surface how can the aerosol it carries get there?  It will form a
blanket even if it is a very low one.

A short life would mean  that we do not have to worry about methane
release.  But can we do enough to cool the re

Re: [geo] Source on SRM causing warming

[Stephen Salter]

 Alan

Pollution is a loaded word.  Check out

http://www.healthandcare.co.uk/great-gifts/salitair-salt-therapy.html?gclid=CNKH0-ur864CFdISfAodwHUpNA

for evidence that breathing salt is very good for people with lung 
diseases.  Osmosis is just as effective as anti-biotics at killing bugs 
but harmless to large organisms  The amount of salt we need to offset 
the thermal effects of double pre-industrial CO2 is about 1% of what is 
put up now by waves breaking on the beach.


Stephen


Emeritus Professor of Engineering Design
Institute for Energy Systems
School of Engineering
Mayfield Road
University of Edinburgh EH9  3JL
Scotland
Tel +44 131 650 5704
Mobile 07795 203 195
www.see.ed.ac.uk/~shs


On 19/03/2012 16:03, Alan Robock wrote:

Dear Mike,

I don't know how you do this 6 to 1 calculation.  We found that the 
e-folding time for stratospheric aerosols in the Arctic s 2-4 months, 
with 4 months in the summer, the relevant time.  (see 
http://climate.envsci.rutgers.edu/pdf/2008JD010050small.pdf )  If we 
compare this to the lifetime of tropospheric aerosols, on week, and 
add a week to the 4 months for their tropospheric time, the ratio is 
130 days to 7 days, which is *19 to 1, not 6 to 1*.  Furthermore, the 
health effects of additional tropospheric pollution are not 
acceptable, in my opinion.


Alan

[On sabbatical for current academic year.  The best way to contact me
is by email,rob...@envsci.rutgers.edu, or at 732-881-1610 (cell).]

Alan Robock, Professor II (Distinguished Professor)
   Editor, Reviews of Geophysics
   Director, Meteorology Undergraduate Program
   Associate Director, Center for Environmental Prediction
Department of Environmental SciencesPhone: +1-732-932-9800 x6222
Rutgers University  Fax: +1-732-932-8644
14 College Farm Road   E-mail:rob...@envsci.rutgers.edu
New Brunswick, NJ 08901-8551  USAhttp://envsci.rutgers.edu/~robock

On 3/18/2012 5:49 PM, Mike MacCracken wrote:

Hi Stephen--My wording must have been confusing.

For stratospheric injections at low latitudes, the lifetime is 1-2 years.
The aerosols do move poleward and are carried into the troposphere in mid
and high latitudes. This is one approach to trying to limit global climate
change, and, as David Keith says, studies indicate that these cool the polar
regions, though perhaps not in the stratosphere.

Your cloud brightening approach is also to limit global warming. I'd also
suggest that we could offset some of the global warming by sulfate aerosols
out over vast ocean areas instead of sulfate's present dominance over, now,
southeastern Asia, China, etc.--so keeping or modestly enhancing the present
cooling offset. [And reducing cirrus may also be a viable approach.]

A third approach is to cool the poles (and this might be good for regional
purposes alone), but cooling also pulls heat out of lower latitudes and
helps to cool them somewhat. The Caldeira-Wood shows it works conceptually
(they reduced solar constant) and Robock et al. injected SO2 into
stratosphere to do (but the full year injection of SO2/SO4 likely spread
some to lower latitudes and the monsoons were affected). One thing Robock et
al. found was that the lifetime of sulfate in the polar stratosphere is
about two months, and so that means that the potential 100 to 1 advantage of
stratospheric sulfate is not valid, and we're down to 6 to 1 compared to
surface-based approaches such as CCN or microbubbles to cool incoming
waters, sulfate or something similar over Arctic area, surface brightening
by microbubbles, etc.--noting that such approaches are only needed (and
effective) for the  few months per year when the Sun is well up in the sky.

As David Keith also says, there is a lot of research to be done to determine
which approaches or alone or in different variants might work, or be
effective or ineffective and have unintended consequences, much less how
such an approach or set of approaches might be integrated with mitigation,
adaptation, suffering, etc.

Best, Mike MacCracken






On 3/18/12 12:52 PM, "Stephen Salter"  wrote:


Mike

I had thought that the plan was stratospheric aerosol to be released at
low latitudes and would slowly migrate to the poles where is would
gracefully descend.  If you can be sure that it will all have gone in 10
days then my concerns vanish.  But if the air cannot get through the
water surface how can the aerosol it carries get there?  It will form a
blanket even if it is a very low one.

A short life would mean  that we do not have to worry about methane
release.  But can we do enough to cool the rest of the planet?  Perhaps
Jon Egil can tell us about blanket lifetime.

Stephen

Mike MacCracken wrote:

The Robock et al simulations of an Arctic injection found that the lifetime
of particles in the lower Arctic stratosphere was only two months. In that
one would only need particles up during the sunlit season (say three months,
for only really helps after the sea i

Re: [geo] Source on SRM causing warming

[Mike MacCracken]

Hi Alan—Well, I got the 2 months number from your paper—and used that.
Interesting that a more detailed evaluation indicates that the lifetime in
summer is longer. I think longer times than a week might well be possible in
the troposphere by choosing injection times and meteorological conditions,
so I’ll correct to ratio of 10 to 20 to 1 for stratosphere, but noting that
there might not be a need for the aerosols to be there for 4 months, so the
longer stratospheric time might be real, but not necessarily relevant.

On the issue of the amount of pollution, a couple of comments. Aside from
arguments over whether it is the sulfate or things with the sulfate causing
the health effects that have been associated with sulfate from coal-fired
power plants (for any sulfate injection it would be pure SO2 or whatever
without all the other combustion products—or perhaps one might use sea salt
or something else), due to past coal use in Europe and Soviet Union, we have
a reasonable sense of what the impacts from sulfate might be. With summer
only injections, one would avoid much of the acid deposition problem
(shorter season, and not accumulating on snow and running off all at once).
One would also be choosing emissions times to have air flows that carry the
SO2/sulfate over the Arctic and not over the land. So, yes, will be some
impacts, but can possibly be moderated to be less than, as your study
suggested, the unintended side effects of stratospheric SO2. I am all for
considering and comparing the full range of possible approaches
(stratospheric, tropospheric, surface, etc.--separately and/or in
combination).

With some sense of what might be able to be done and the potential impacts,
the next step is a comparative risk evaluation, as for all climate
engineering. Without doing something, it is hard to see how the Arctic can
be kept from very extensive thawing and loss of the climate that we have.
With it, yes, some different types of impacts due to the engineering effort,
but, assuming it works, a good deal less, or slowed climate impact on the
Arctic, and if loss of glacier/ice sheet mass can be slowed (or reversed—as
Caldeira-Wood study suggested), then a benefit to the global community.

With some sense of relative risks of various choices, it becomes a political
decision, with its many considerations. I happen to think that, if any
climate engineering is to be considered, having a focused goal such as
limiting polar warming and associated impacts would be more likely to be
considered as a first step than jumping straight to a global
counter-balancing approach, but that is just my opinion. In any case, rather
than saying what is or is not acceptable, it seems to me our responsibility
is to explore and evaluate options and then it is the governance system that
decides about the tradeoffs of pollution versus un- (or under-) moderated
Arctic change (and everything else).

Mike


On 3/19/12 12:03 PM, "Alan Robock"  wrote:

>Dear Mike,
>  
>  I don't know how you do this 6 to 1 calculation.  We found that the e-folding
> time for stratospheric aerosols in the Arctic s 2-4 months, with 4 months in
> the summer, the relevant time.  (see
> http://climate.envsci.rutgers.edu/pdf/2008JD010050small.pdf )  If we compare
> this to the lifetime of tropospheric aerosols, on week, and add a week to the
> 4 months for their tropospheric time, the ratio is 130 days to 7 days, which
> is 19 to 1, not 6 to 1.  Furthermore, the health effects of additional
> tropospheric pollution are not acceptable, in my opinion.
>  
>
> Alan
> 
> [On sabbatical for current academic year.  The best way to contact me
> is by email, rob...@envsci.rutgers.edu, or at 732-881-1610 (cell).]
> 
> Alan Robock, Professor II (Distinguished Professor)
>   Editor, Reviews of Geophysics
>   Director, Meteorology Undergraduate Program
>   Associate Director, Center for Environmental Prediction
> Department of Environmental SciencesPhone: +1-732-932-9800 x6222
> Rutgers University  Fax: +1-732-932-8644
> 14 College Farm Road   E-mail: rob...@envsci.rutgers.edu
> New Brunswick, NJ 08901-8551  USA  http://envsci.rutgers.edu/~robock
>  
>  On 3/18/2012 5:49 PM, Mike MacCracken wrote:
>>  
>> Hi Stephen--My wording must have been confusing.
>> 
>> For stratospheric injections at low latitudes, the lifetime is 1-2 years.
>> The aerosols do move poleward and are carried into the troposphere in mid
>> and high latitudes. This is one approach to trying to limit global climate
>> change, and, as David Keith says, studies indicate that these cool the polar
>> regions, though perhaps not in the stratosphere.
>> 
>> Your cloud brightening approach is also to limit global warming. I'd also
>> suggest that we could offset some of the global warming by sulfate aerosols
>> out over vast ocean areas instead of sulfate's present dominance over, now,
>> southeastern Asia, China, etc.--so keeping or modestly enhanci

RE: [geo] Source on SRM causing warming

[David Keith]

And... this 2-4 month lifetime is very altitude and latitude dependent.

We can run some sims with the AER 2D an look but my guess from what we have 
done is that you could make choices that would push this up a bit.

David


From: geoengineering@googlegroups.com [mailto:geoengineering@googlegroups.com] 
On Behalf Of Alan Robock
Sent: Monday, March 19, 2012 10:03 AM
To: mmacc...@comcast.net
Cc: Stephen Salter; Ken Caldeira; Andrew Lockley; Geoengineering; 
j.e.kristjans...@geo.uio.no
Subject: Re: [geo] Source on SRM causing warming

Dear Mike,

I don't know how you do this 6 to 1 calculation.  We found that the e-folding 
time for stratospheric aerosols in the Arctic s 2-4 months, with 4 months in 
the summer, the relevant time.  (see 
http://climate.envsci.rutgers.edu/pdf/2008JD010050small.pdf )  If we compare 
this to the lifetime of tropospheric aerosols, on week, and add a week to the 4 
months for their tropospheric time, the ratio is 130 days to 7 days, which is 
19 to 1, not 6 to 1.  Furthermore, the health effects of additional 
tropospheric pollution are not acceptable, in my opinion.




Alan



[On sabbatical for current academic year.  The best way to contact me

is by email, rob...@envsci.rutgers.edu, or at 
732-881-1610 (cell).]



Alan Robock, Professor II (Distinguished Professor)

  Editor, Reviews of Geophysics

  Director, Meteorology Undergraduate Program

  Associate Director, Center for Environmental Prediction

Department of Environmental SciencesPhone: +1-732-932-9800 x6222

Rutgers University  Fax: +1-732-932-8644

14 College Farm Road   E-mail: 
rob...@envsci.rutgers.edu

New Brunswick, NJ 08901-8551  USA  http://envsci.rutgers.edu/~robock

On 3/18/2012 5:49 PM, Mike MacCracken wrote:

Hi Stephen--My wording must have been confusing.



For stratospheric injections at low latitudes, the lifetime is 1-2 years.

The aerosols do move poleward and are carried into the troposphere in mid

and high latitudes. This is one approach to trying to limit global climate

change, and, as David Keith says, studies indicate that these cool the polar

regions, though perhaps not in the stratosphere.



Your cloud brightening approach is also to limit global warming. I'd also

suggest that we could offset some of the global warming by sulfate aerosols

out over vast ocean areas instead of sulfate's present dominance over, now,

southeastern Asia, China, etc.--so keeping or modestly enhancing the present

cooling offset. [And reducing cirrus may also be a viable approach.]



A third approach is to cool the poles (and this might be good for regional

purposes alone), but cooling also pulls heat out of lower latitudes and

helps to cool them somewhat. The Caldeira-Wood shows it works conceptually

(they reduced solar constant) and Robock et al. injected SO2 into

stratosphere to do (but the full year injection of SO2/SO4 likely spread

some to lower latitudes and the monsoons were affected). One thing Robock et

al. found was that the lifetime of sulfate in the polar stratosphere is

about two months, and so that means that the potential 100 to 1 advantage of

stratospheric sulfate is not valid, and we're down to 6 to 1 compared to

surface-based approaches such as CCN or microbubbles to cool incoming

waters, sulfate or something similar over Arctic area, surface brightening

by microbubbles, etc.--noting that such approaches are only needed (and

effective) for the  few months per year when the Sun is well up in the sky.



As David Keith also says, there is a lot of research to be done to determine

which approaches or alone or in different variants might work, or be

effective or ineffective and have unintended consequences, much less how

such an approach or set of approaches might be integrated with mitigation,

adaptation, suffering, etc.



Best, Mike MacCracken













On 3/18/12 12:52 PM, "Stephen Salter" 
 wrote:



Mike



I had thought that the plan was stratospheric aerosol to be released at

low latitudes and would slowly migrate to the poles where is would

gracefully descend.  If you can be sure that it will all have gone in 10

days then my concerns vanish.  But if the air cannot get through the

water surface how can the aerosol it carries get there?  It will form a

blanket even if it is a very low one.



A short life would mean  that we do not have to worry about methane

release.  But can we do enough to cool the rest of the planet?  Perhaps

Jon Egil can tell us about blanket lifetime.



Stephen



Mike MacCracken wrote:

The Robock et al simulations of an Arctic injection found that the lifetime

of particles in the lower Arctic stratosphere was only two months. In that

one would only need particles up during the sunlit season (say three months,

for only really helps after the sea ice surface has melted and the sun i

RE: [geo] Source on SRM causing warming

[David Keith]

The acid deposition problem may well carry less weigh than the contribution to 
trop chemistry and air pollution.

D

From: geoengineering@googlegroups.com [mailto:geoengineering@googlegroups.com] 
On Behalf Of Mike MacCracken
Sent: Monday, March 19, 2012 10:43 AM
To: Alan Robock
Cc: Stephen Salter; Ken Caldeira; Andrew Lockley; Geoengineering; 
j.e.kristjans...@geo.uio.no
Subject: Re: [geo] Source on SRM causing warming

Hi Alan-Well, I got the 2 months number from your paper-and used that. 
Interesting that a more detailed evaluation indicates that the lifetime in 
summer is longer. I think longer times than a week might well be possible in 
the troposphere by choosing injection times and meteorological conditions, so 
I'll correct to ratio of 10 to 20 to 1 for stratosphere, but noting that there 
might not be a need for the aerosols to be there for 4 months, so the longer 
stratospheric time might be real, but not necessarily relevant.

On the issue of the amount of pollution, a couple of comments. Aside from 
arguments over whether it is the sulfate or things with the sulfate causing the 
health effects that have been associated with sulfate from coal-fired power 
plants (for any sulfate injection it would be pure SO2 or whatever without all 
the other combustion products-or perhaps one might use sea salt or something 
else), due to past coal use in Europe and Soviet Union, we have a reasonable 
sense of what the impacts from sulfate might be. With summer only injections, 
one would avoid much of the acid deposition problem (shorter season, and not 
accumulating on snow and running off all at once). One would also be choosing 
emissions times to have air flows that carry the SO2/sulfate over the Arctic 
and not over the land. So, yes, will be some impacts, but can possibly be 
moderated to be less than, as your study suggested, the unintended side effects 
of stratospheric SO2. I am all for considering and comparing the full range of 
possible approaches (stratospheric, tropospheric, surface, etc.--separately 
and/or in combination).

With some sense of what might be able to be done and the potential impacts, the 
next step is a comparative risk evaluation, as for all climate engineering. 
Without doing something, it is hard to see how the Arctic can be kept from very 
extensive thawing and loss of the climate that we have. With it, yes, some 
different types of impacts due to the engineering effort, but, assuming it 
works, a good deal less, or slowed climate impact on the Arctic, and if loss of 
glacier/ice sheet mass can be slowed (or reversed-as Caldeira-Wood study 
suggested), then a benefit to the global community.

With some sense of relative risks of various choices, it becomes a political 
decision, with its many considerations. I happen to think that, if any climate 
engineering is to be considered, having a focused goal such as limiting polar 
warming and associated impacts would be more likely to be considered as a first 
step than jumping straight to a global counter-balancing approach, but that is 
just my opinion. In any case, rather than saying what is or is not acceptable, 
it seems to me our responsibility is to explore and evaluate options and then 
it is the governance system that decides about the tradeoffs of pollution 
versus un- (or under-) moderated Arctic change (and everything else).

Mike


On 3/19/12 12:03 PM, "Alan Robock"  wrote:
  Dear Mike,

 I don't know how you do this 6 to 1 calculation.  We found that the e-folding 
time for stratospheric aerosols in the Arctic s 2-4 months, with 4 months in 
the summer, the relevant time.  (see 
http://climate.envsci.rutgers.edu/pdf/2008JD010050small.pdf )  If we compare 
this to the lifetime of tropospheric aerosols, on week, and add a week to the 4 
months for their tropospheric time, the ratio is 130 days to 7 days, which is 
19 to 1, not 6 to 1.  Furthermore, the health effects of additional 
tropospheric pollution are not acceptable, in my opinion.


Alan

[On sabbatical for current academic year.  The best way to contact me
is by email, rob...@envsci.rutgers.edu, or at 732-881-1610 (cell).]

Alan Robock, Professor II (Distinguished Professor)
  Editor, Reviews of Geophysics
  Director, Meteorology Undergraduate Program
  Associate Director, Center for Environmental Prediction
Department of Environmental SciencesPhone: +1-732-932-9800 x6222
Rutgers University  Fax: +1-732-932-8644
14 College Farm Road   E-mail: rob...@envsci.rutgers.edu
New Brunswick, NJ 08901-8551  USA  http://envsci.rutgers.edu/~robock

 On 3/18/2012 5:49 PM, Mike MacCracken wrote:

Hi Stephen--My wording must have been confusing.

For stratospheric injections at low latitudes, the lifetime is 1-2 years.
The aerosols do move poleward and are carried into the troposphere in mid
and high latitudes. This is one approach to trying to limit global climate
change, and, as David Keith says, studies indicat

Re: [geo] Source on SRM causing warming

[Alan Robock]

Dear Mike,

The paper says:

There is a clear seasonal cycle in the e-folding lifetime of
the stratospheric aerosols in the Arctic case ranging from
2 to 4 months. The maximum lifetime occurs during boreal
summer with a minimum during boreal winter with the
formation of the polar vortex and higher rates of tropopause
folding.

So 4 months is the correct number to use if you are looking at a ratio 
of impact to mass of sulfur injections.



Alan

[On sabbatical for current academic year.  The best way to contact me
is by email, rob...@envsci.rutgers.edu, or at 732-881-1610 (cell).]

Alan Robock, Professor II (Distinguished Professor)
  Editor, Reviews of Geophysics
  Director, Meteorology Undergraduate Program
  Associate Director, Center for Environmental Prediction
Department of Environmental SciencesPhone: +1-732-932-9800 x6222
Rutgers University  Fax: +1-732-932-8644
14 College Farm Road   E-mail: rob...@envsci.rutgers.edu
New Brunswick, NJ 08901-8551  USA  http://envsci.rutgers.edu/~robock


On 3/19/2012 9:42 AM, Mike MacCracken wrote:
Hi Alan---Well, I got the 2 months number from your paper---and used 
that. Interesting that a more detailed evaluation indicates that the 
lifetime in summer is longer. I think longer times than a week might 
well be possible in the troposphere by choosing injection times and 
meteorological conditions, so I'll correct to ratio of 10 to 20 to 1 
for stratosphere, but noting that there might not be a need for the 
aerosols to be there for 4 months, so the longer stratospheric time 
might be real, but not necessarily relevant.


On the issue of the amount of pollution, a couple of comments. Aside 
from arguments over whether it is the sulfate or things with the 
sulfate causing the health effects that have been associated with 
sulfate from coal-fired power plants (for any sulfate injection it 
would be pure SO2 or whatever without all the other combustion 
products---or perhaps one might use sea salt or something else), due 
to past coal use in Europe and Soviet Union, we have a reasonable 
sense of what the impacts from sulfate might be. With summer only 
injections, one would avoid much of the acid deposition problem 
(shorter season, and not accumulating on snow and running off all at 
once). One would also be choosing emissions times to have air flows 
that carry the SO2/sulfate over the Arctic and not over the land. So, 
yes, will be some impacts, but can possibly be moderated to be less 
than, as your study suggested, the unintended side effects of 
stratospheric SO2. I am all for considering and comparing the full 
range of possible approaches (stratospheric, tropospheric, surface, 
etc.--separately and/or in combination).


With some sense of what might be able to be done and the potential 
impacts, the next step is a comparative risk evaluation, as for all 
climate engineering. Without doing something, it is hard to see how 
the Arctic can be kept from very extensive thawing and loss of the 
climate that we have. With it, yes, some different types of impacts 
due to the engineering effort, but, assuming it works, a good deal 
less, or slowed climate impact on the Arctic, and if loss of 
glacier/ice sheet mass can be slowed (or reversed---as Caldeira-Wood 
study suggested), then a benefit to the global community.


With some sense of relative risks of various choices, it becomes a 
political decision, with its many considerations. I happen to think 
that, if any climate engineering is to be considered, having a focused 
goal such as limiting polar warming and associated impacts would be 
more likely to be considered as a first step than jumping straight to 
a global counter-balancing approach, but that is just my opinion. In 
any case, rather than saying what is or is not acceptable, it seems to 
me our responsibility is to explore and evaluate options and then it 
is the governance system that decides about the tradeoffs of pollution 
versus un- (or under-) moderated Arctic change (and everything else).


Mike


On 3/19/12 12:03 PM, "Alan Robock"  wrote:

  Dear Mike,

 I don't know how you do this 6 to 1 calculation.  We found that
the e-folding time for stratospheric aerosols in the Arctic s 2-4
months, with 4 months in the summer, the relevant time.  (see
http://climate.envsci.rutgers.edu/pdf/2008JD010050small.pdf )  If
we compare this to the lifetime of tropospheric aerosols, on week,
and add a week to the 4 months for their tropospheric time, the
ratio is 130 days to 7 days, which is *19 to 1, not 6 to 1*.
 Furthermore, the health effects of additional tropospheric
pollution are not acceptable, in my opinion.


Alan

[On sabbatical for current academic year.  The best way to contact me
is by email, rob...@envsci.rutgers.edu, or at 732-881-1610 (cell).]

Alan Robock, Professor II (Distinguished Professor)
  Editor, Reviews of Geophysics
  

Re: [geo] Source on SRM causing warming

[Andrew Lockley]

Doesn't lifetime depend massively on injection height & particle size?
Size in turn depends on precursor, injection density, weather etc.

What is the latest thinking on the preferred precursor and injection
conditions? Acid mist, SO2 or H2S?

A
On Mar 19, 2012 4:43 PM, "Mike MacCracken"  wrote:

>  Hi Alan—Well, I got the 2 months number from your paper—and used that.
> Interesting that a more detailed evaluation indicates that the lifetime in
> summer is longer. I think longer times than a week might well be possible
> in the troposphere by choosing injection times and meteorological
> conditions, so I’ll correct to ratio of 10 to 20 to 1 for stratosphere, but
> noting that there might not be a need for the aerosols to be there for 4
> months, so the longer stratospheric time might be real, but not necessarily
> relevant.
>
> On the issue of the amount of pollution, a couple of comments. Aside from
> arguments over whether it is the sulfate or things with the sulfate causing
> the health effects that have been associated with sulfate from coal-fired
> power plants (for any sulfate injection it would be pure SO2 or whatever
> without all the other combustion products—or perhaps one might use sea salt
> or something else), due to past coal use in Europe and Soviet Union, we
> have a reasonable sense of what the impacts from sulfate might be. With
> summer only injections, one would avoid much of the acid deposition problem
> (shorter season, and not accumulating on snow and running off all at once).
> One would also be choosing emissions times to have air flows that carry the
> SO2/sulfate over the Arctic and not over the land. So, yes, will be some
> impacts, but can possibly be moderated to be less than, as your study
> suggested, the unintended side effects of stratospheric SO2. I am all for
> considering and comparing the full range of possible approaches
> (stratospheric, tropospheric, surface, etc.--separately and/or in
> combination).
>
> With some sense of what might be able to be done and the potential
> impacts, the next step is a comparative risk evaluation, as for all climate
> engineering. Without doing something, it is hard to see how the Arctic can
> be kept from very extensive thawing and loss of the climate that we have.
> With it, yes, some different types of impacts due to the engineering
> effort, but, assuming it works, a good deal less, or slowed climate impact
> on the Arctic, and if loss of glacier/ice sheet mass can be slowed (or
> reversed—as Caldeira-Wood study suggested), then a benefit to the global
> community.
>
> With some sense of relative risks of various choices, it becomes a
> political decision, with its many considerations. I happen to think that,
> if any climate engineering is to be considered, having a focused goal such
> as limiting polar warming and associated impacts would be more likely to be
> considered as a first step than jumping straight to a global
> counter-balancing approach, but that is just my opinion. In any case,
> rather than saying what is or is not acceptable, it seems to me our
> responsibility is to explore and evaluate options and then it is the
> governance system that decides about the tradeoffs of pollution versus un-
> (or under-) moderated Arctic change (and everything else).
>
> Mike
>
>
> On 3/19/12 12:03 PM, "Alan Robock"  wrote:
>
>Dear Mike,
>
>  I don't know how you do this 6 to 1 calculation.  We found that the
> e-folding time for stratospheric aerosols in the Arctic s 2-4 months, with
> 4 months in the summer, the relevant time.  (see
> http://climate.envsci.rutgers.edu/pdf/2008JD010050small.pdf )  If we
> compare this to the lifetime of tropospheric aerosols, on week, and add a
> week to the 4 months for their tropospheric time, the ratio is 130 days to
> 7 days, which is *19 to 1, not 6 to 1*.  Furthermore, the health effects
> of additional tropospheric pollution are not acceptable, in my opinion.
>
>
> Alan
>
> [On sabbatical for current academic year.  The best way to contact me
> is by email, rob...@envsci.rutgers.edu, or at 732-881-1610 (cell).]
>
> Alan Robock, Professor II (Distinguished Professor)
>   Editor, Reviews of Geophysics
>   Director, Meteorology Undergraduate Program
>   Associate Director, Center for Environmental Prediction
> Department of Environmental SciencesPhone: +1-732-932-9800 x6222
> Rutgers University  Fax: +1-732-932-8644
> 14 College Farm Road   E-mail: rob...@envsci.rutgers.edu
> New Brunswick, NJ 08901-8551  USA  http://envsci.rutgers.edu/~robock
>
>  On 3/18/2012 5:49 PM, Mike MacCracken wrote:
>
>
> Hi Stephen--My wording must have been confusing.
>
> For stratospheric injections at low latitudes, the lifetime is 1-2 years.
> The aerosols do move poleward and are carried into the troposphere in mid
> and high latitudes. This is one approach to trying to limit global climate
> change, and, as David Keith says, studies indicate that

Re: [geo] Source on SRM causing warming

[Mike MacCracken]

Hi Alan—Well, my mistake—I thought I got the 2-month number from your paper
on this, but apparently not.

Mike


On 3/19/12 1:12 PM, "Alan Robock"  wrote:

>Dear Mike,
>  
>  The paper says:
>  
>  There is a clear seasonal cycle in the e-folding lifetime of
>  the stratospheric aerosols in the Arctic case ranging from
>  2 to 4 months. The maximum lifetime occurs during boreal
>  summer with a minimum during boreal winter with the
>  formation of the polar vortex and higher rates of tropopause
>  folding.
>  
>  So 4 months is the correct number to use if you are looking at a ratio of
> impact to mass of sulfur injections.
>  
>
> Alan
> 
> [On sabbatical for current academic year.  The best way to contact me
> is by email, rob...@envsci.rutgers.edu, or at 732-881-1610 (cell).]
> 
> Alan Robock, Professor II (Distinguished Professor)
>   Editor, Reviews of Geophysics
>   Director, Meteorology Undergraduate Program
>   Associate Director, Center for Environmental Prediction
> Department of Environmental SciencesPhone: +1-732-932-9800 x6222
> Rutgers University  Fax: +1-732-932-8644
> 14 College Farm Road   E-mail: rob...@envsci.rutgers.edu
> New Brunswick, NJ 08901-8551  USA  http://envsci.rutgers.edu/~robock
>  
>  On 3/19/2012 9:42 AM, Mike MacCracken wrote:
>>  Re: [geo] Source on SRM causing warming Hi Alan—Well, I got the 2 months
>> number from your paper—and used that. Interesting that a more detailed
>> evaluation indicates that the lifetime in summer is longer. I think longer
>> times than a week might well be possible in the troposphere by choosing
>> injection times and meteorological conditions, so I’ll correct to ratio of 10
>> to 20 to 1 for stratosphere, but noting that there might not be a need for
>> the aerosols to be there for 4 months, so the longer stratospheric time might
>> be real, but not necessarily relevant.
>>  
>>  On the issue of the amount of pollution, a couple of comments. Aside from
>> arguments over whether it is the sulfate or things with the sulfate causing
>> the health effects that have been associated with sulfate from coal-fired
>> power plants (for any sulfate injection it would be pure SO2 or whatever
>> without all the other combustion products—or perhaps one might use sea salt
>> or something else), due to past coal use in Europe and Soviet Union, we have
>> a reasonable sense of what the impacts from sulfate might be. With summer
>> only injections, one would avoid much of the acid deposition problem (shorter
>> season, and not accumulating on snow and running off all at once). One would
>> also be choosing emissions times to have air flows that carry the SO2/sulfate
>> over the Arctic and not over the land. So, yes, will be some impacts, but can
>> possibly be moderated to be less than, as your study suggested, the
>> unintended side effects of stratospheric SO2. I am all for considering and
>> comparing the full range of possible approaches (stratospheric, tropospheric,
>> surface, etc.--separately and/or in combination).
>>  
>>  With some sense of what might be able to be done and the potential impacts,
>> the next step is a comparative risk evaluation, as for all climate
>> engineering. Without doing something, it is hard to see how the Arctic can be
>> kept from very extensive thawing and loss of the climate that we have. With
>> it, yes, some different types of impacts due to the engineering effort, but,
>> assuming it works, a good deal less, or slowed climate impact on the Arctic,
>> and if loss of glacier/ice sheet mass can be slowed (or reversed—as
>> Caldeira-Wood study suggested), then a benefit to the global community.
>>  
>>  With some sense of relative risks of various choices, it becomes a political
>> decision, with its many considerations. I happen to think that, if any
>> climate engineering is to be considered, having a focused goal such as
>> limiting polar warming and associated impacts would be more likely to be
>> considered as a first step than jumping straight to a global
>> counter-balancing approach, but that is just my opinion. In any case, rather
>> than saying what is or is not acceptable, it seems to me our responsibility
>> is to explore and evaluate options and then it is the governance system that
>> decides about the tradeoffs of pollution versus un- (or under-) moderated
>> Arctic change (and everything else).
>>  
>>  Mike
>>  
>>  
>>  On 3/19/12 12:03 PM, "Alan Robock"  wrote:
>>  
>>   
>>>Dear Mike,
>>>   
>>>   I don't know how you do this 6 to 1 calculation.  We found that the
>>> e-folding time for stratospheric aerosols in the Arctic s 2-4 months, with 4
>>> months in the summer, the relevant time.  (see
>>> http://climate.envsci.rutgers.edu/pdf/2008JD010050small.pdf )  If we compare
>>> this to the lifetime of tropospheric aerosols, on week, and add a week to
>>> the 4 months for their tropospheric time, the ratio is 130 days to 7 days,
>>> w

Re: [geo] Re: tropospheric aerosol use

[John Nissen]

Hi Nathan,

Thanks for that thoughtful posting.  I am sorry you have the impression
that AMEG might be proposing cloud brightening as a silver bullet.  We
obviously have a strong advocate of that particular method in Stephen
Salter, who is a member of the group.  But Stephen recognises that we have
an emergency situation because of the rapidity of sea ice retreat, with a
possible collapse of sea ice extent this summer.  So measures have to be
taken quickly, ideally within the next few weeks.  Stephen is considering
having the spray for cloud brightening on land (e.g. Faroes) rather than on
ships.  But, even with government backing, this might still take a year or
two to get going.  Meanwhile we have to think of measures that could be
taken more quickly.  At least we have to avoid unnecessary heating.
Obviously we must avoid "termination" effects - particularly the warming
that will happen if/when they start to remove sulphur from ship fuel.
Stephen quoted a figure of -0.6 Watts/m-2 from that, if I remember.  Anyway
ships have a surprisingly large cooling effect!

But your idea of deliberately adding sulphate aerosol to the troposphere at
appropriate locations might be something which could be implemented very
quickly as a temporary measure band-aid, so has to be on the table.  And if
this has the effect of suppressing methane in wetlands (a major contributor
to the methane level in the atmosphere), so much the better.

BTW, as engineers, we are seeking to obtain a cooling effect of the order
of half a petawatt into the Arctic to halt the sea ice retreat.

Cheers,

John

On Sun, Mar 18, 2012 at 6:28 AM, Nathan Currier wrote:

> Thanks for the responses - though what I had in mind was actually more
> in line with the tenor of Mike's latest comments about the 6-to-1
> lifetime ratio for arctic sulfur SRM, stratospheric vs. tropospheric,
> etc.
>
> David’s early article is very impressive for how much it adumbrated
> the current public discourse on geoengineering, though at the same
> time, a bit of misunderstanding about what I was intending to ask –
> and I was probably not expressing myself very well – possibly
> underscores how something really has been shifting lately within the
> geoengineering world, too. What I meant about tropospheric sulfur
> injections was entirely in the newer sense of a more ‘localized
> geoengineering’, which has been getting attention here in this group
> lately (so much so that I forgot to mention what I meant in my
> question), and which I think makes a world of difference in
> considering its use. In a sense, stratospheric injections can’t be
> effectively localized, and this newer local thinking - coming in
> response to events on the ground - might bring out new ways of
> considering tropospheric sulfur versus stratospheric sulfur, as Mike’s
> comments from earlier today in that other thread show, and the issue
> of sulfur's dangers, which are the main point in David's comments, are
> clearly altered by the reduced scale of use.
>
> In the BBC article that Andrew has just posted, Pete Wadhams is
> talking about AMEG’s plans should the methane situation there
> deteriorate a good deal further (which seems almost certain, if I had
> to guess), and they focus on MCB alone. I think I had first seen
> mention here of tropospheric sulfur injections in this context from
> Mike, and this really took off in my imagination when I by chance
> shortly afterward saw some work involving Eileen Matthews (Gauci et
> al) showing how strongly just ordinary levels of acid rain will impede
> methanogenesis in wetlands, with strong reductions, like 40% or so,
> which play out through considerably longer time periods than the brief
> atmospheric lifetime of the aerosols.
>
> I think study of this combined methane-SRM effect for tropospheric
> sulfur injection should really be done. Curiously, David, in what you
> sent me, the abstract on intercontinental effects of SO2 don’t suggest
> that Russia is particularly bad for that particular concern, less so
> than Europe, for example. And curiously, I might add, despite what you
> just wrote, in your early paper you had actually listed stratospheric
> injections as more dangerous than tropospheric (although I assume for
> entirely different reasons, related then to ozone loss concerns, etc).
>
> But this is really something very different now from all that, or from
> Budyko’s early comparisons of efficiency, lifetimes, etc. We’re
> talking about a very limited area for treatment, almost nothing by
> comparison with plans to geoengineer a global –1W/m2 or some such
> thing. And currently one third of the land area of China is
> experiencing acid rain, I recently read. How could it be acceptable to
> add copious amounts of sulfur to one of the most densely populated
> parts of the planet, which will clearly lead to considerable mortality
> and sickness, and unacceptable to add any sulfur at all to a mostly
> unpopulated area around the mouth of the Len