Considering all effects, what's your view on the ideal height?
Andrew
On Tue, 17 Dec 2019, 08:47 Govindasamy Bala, <bala....@gmail.com
<mailto:bala....@gmail.com>> wrote:
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
<andrew.lock...@gmail.com <mailto:andrew.lock...@gmail.com>> wrote:
Is 26k less good than 25?
On Tue, 17 Dec 2019, 08:37 Govindasamy Bala,
<bala....@gmail.com <mailto:bala....@gmail.com>> 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
<andrew.lock...@gmail.com
<mailto:andrew.lock...@gmail.com>> wrote:
So what's your judgement on the ideal injection altitude?
Andrew
On Mon, 16 Dec 2019, 10:36 Govindasamy Bala,
<bala....@gmail.com <mailto:bala....@gmail.com>> 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
<mailto: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,
<bala....@gmail.com
<mailto:bala....@gmail.com>> 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 <dgm...@cornell.edu
<mailto:dgm...@cornell.edu>> 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
<mailto:geoengineering@googlegroups.com>
<geoengineering@googlegroups.com
<mailto:geoengineering@googlegroups.com>>
*On Behalf Of *Govindasamy Bala
*Sent:* Saturday, December 14, 2019
9:38 PM
*To:* Andrew Lockley
<andrew.lock...@gmail.com
<mailto:andrew.lock...@gmail.com>>
*Cc:* geoengineering
<geoengineering@googlegroups.com
<mailto:geoengineering@googlegroups.com>>
*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
<mailto: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 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 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.
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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
<mailto:gb...@iisc.ac.in>; bala.gov
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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
<mailto:gb...@iisc.ac.in>; bala.gov
<http://bala.gov>@gmail.com <http://gmail.com>
Web:http://dccc.iisc.ac.in/dr_govindasamy_bala_profile.html
-------------------------------------------------------------------
--
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 <mailto:gb...@iisc.ac.in>;
bala.gov <http://bala.gov>@gmail.com
<http://gmail.com>
Web:http://dccc.iisc.ac.in/dr_govindasamy_bala_profile.html
-------------------------------------------------------------------
--
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 <mailto:gb...@iisc.ac.in>;
bala.gov <http://bala.gov>@gmail.com <http://gmail.com>
Web:http://dccc.iisc.ac.in/dr_govindasamy_bala_profile.html
-------------------------------------------------------------------
--
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 <mailto:gb...@iisc.ac.in>; bala.gov
<http://bala.gov>@gmail.com <http://gmail.com>
Web:http://dccc.iisc.ac.in/dr_govindasamy_bala_profile.html
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