This depends on the objective. For a global aerosol program designed to stop
the warming of the entire planet, the answer is no. In this case, we want the
aerosol to stay suspended as long as possible to get the maximum amount of
sunlight scattering and to minimize the quantity of precursor that has to be
transported to the stratosphere. The longer lived aerosol would also tend to
be less of a problem in ozone depletion as the surface area would be reduced
relative to larger shorter lived droplets.
If the aerosol precursor is released in the tropical stratosphere, it will
circle and cover the entire globe, including India. Releases outside the
tropics could be attempted, but this would create uneven warming of a different
kind and a good portion of India and all of China is outside the tropics anyway.
In the case of an Arctic only aerosol program, the aerosol size issue is
probably the same, but the supporters have set as criteria releasing the
precursor in the upper troposphere (around 45,000 ft) in the spring with the
goal of having it all gone by the end of the summer. This would minimize any
ozone depletion as the aerosol would have to be present in the winter for the
"dark" reactions to take place. Having the aerosol active only during the
summer might lessen or have no impact on monsoons or other seasonal rainfall
patterns. There is no data to support this one way or the other.
Note also that the limited modeling done to date in addition to the resolution
of regional impacts issue mentioned earlier today also has focussed almost
entirely on high loading of aerosol precursor to simulate that required to
offset a doubling of CO2 from pre-industrial. While these extreme conditions
may actually be required at some point decades from now, a more likely scenario
is one of a gradual incremental increase in the aerosol to match GHG forcing or
to offset loss of tropospheric aerosols. In such cases, the climate system may
adjust and there may be no impact on monsoonal flows or precipitation or the
effect may be very gradual and so can be dealt with by adaptation. The point
is we simply don't know because these studies haven't been done. Thus the risk
questions posed by John Nissen represent work that needs to be done.
----- Original Message -----
From: Andrew Lockley
To: John Nissen
Cc: Alvia Gaskill ; s.sal...@ed.ac.uk ; rob...@envsci.rutgers.edu ;
kcalde...@dge.stanford.edu ; xbenf...@aol.com ; geoengineering@googlegroups.com
; brian.laun...@manchester.ac.uk ; sam.car...@gmail.com ; p...@cam.ac.uk
Sent: Saturday, May 09, 2009 8:01 PM
Subject: Re: [geo] Re: Balancing the pros and cons of geoengineering
Can't we modify the aerosol size, and deployment patterns, to make sure they
fall out quickly and don't go anywhere near India?
A
2009/5/9 John Nissen <j...@cloudworld.co.uk>
Very good discussion.
I'm trying to get a balance of pros (benefits B1-B7) and cons (specific
fears S1-S21). What I'd like out of our discussion is some kind of risk
assessment for the possible downside of a weaker monsoon, as this is considered
the biggest risk in the regional effects (S1). And we could make this
reasonably pessimistic, to be on the safe side - i.e. be cautious with the
application of geoengineering. On the other hand, we might be able to reduce
this risk, e.g. by neutralising sulphate aerosol; if there's a good chance of
this working, then we can factor that into the calculation. Or the risk might
be offset by a benefit in that region, e.g. improved summer water supply from
Himalayan glaciers?
So, what kind of impact would a weaker monsoon (ISM) have on India? What
is the probability of stratospheric aerosols deployed in the Arctic would
produce a weaker monsoon? Can this risk be significantly countered? Can it be
significantly offset?
Note that the risk on benefit side might be measured in terms of a risk,
without geoengineering, of millions or even billions of lives being lost
(especially if massive methane release adds several degrees of global warming,
B4). Alternatively we could measure in GDP lost - current global GDP (aka GWP)
is about $60 trillion I believe.
Cheers,
John
----- Original Message ----- From: "Alvia Gaskill" <agask...@nc.rr.com>
To: <s.sal...@ed.ac.uk>; <rob...@envsci.rutgers.edu>
Cc: <kcalde...@dge.stanford.edu>; "Andrew Lockley"
<andrew.lock...@gmail.com>; <xbenf...@aol.com>; <j...@cloudworld.co.uk>;
<geoengineering@googlegroups.com>; <brian.laun...@manchester.ac.uk>;
<sam.car...@gmail.com>; <p...@cam.ac.uk>
Sent: Saturday, May 09, 2009 4:50 PM
Subject: Re: [geo] Re: Balancing the pros and cons of geoengineering
Stephen makes a good point that leads to a more general one. If there
are precipitation reductions associated with sunlight blocking schemes,
consideration should also be given to mitigating these, analogous to the
medications given to patients with Type II diabetes to combat the side effects
of the primary drug.
This is an oversimplification, but the way summer monsoons work is that
in the summer the land gets warmer than the ocean faster, creating a low
pressure area and this causes on shore flow as air moves from high to low
presssure. For some reason, Laki caused this to be muted. There were no
aerosols from Laki over India and it has been suggested there was a
teleconnected response (see the paper Stephen attached) although in paleo
climate the authors say the effects were direct, but don't give specifics. In
the case of Pinatubo, both the land and sea were cooled by the aerosol and the
land simply didn't heat up fast enough to generate the on shore flow.
If the Arctic only aerosol geoengineering does cause a reduction in the
ISM (Indian Summer Monsoon as there are other monsoons that affect India, but
this is the most important one), use of the cloud whitening to restore at least
some of the temperature differential should be considered. Likewise, in a
global aerosol scheme, with a global aerosol spread similar to that of
Pinatubo, the cloud whitening could also be used to create a temperature
differential, but at some point it becomes a race to the bottom, with the land
temperature simply too cool to initiate the low pressure area. In this case,
reducing the depth of the aerosol layer over the land may be the most effective
way to restore the dynamics.
I previously suggested using ammonia released from either planes or
balloons to react with the sulfate aerosol and drop them out as ammonium
sulfate. This idea as well as Stephen's could be applied to other locations
such as the Amazon, Eastern China and Africa where models indicate unacceptable
reductions in precipitation are a result of either aerosol geoengineering or
global warming. Of course, the ammonia wouldn't be of any value in a global
warming/no aerosol scenario.
I said in one the earliest papers I wrote on geoengineering that
eventually we were going to have to learn how to manipulate the climate to our
advantage. That includes both gross scale and fine tuning.
In a related issue, last year I posted a link from a group in the UK that
was carrying out some 130 different models of aerosol geoengineering. It was a
volunteer effort among universities. If they have done even a fraction of the
modeling, this work should be taken into account in designing new studies such
as Rutgers is proposing. Anyone have an update?
You may recall also that we spent some time last year discussing the
significance of the "little brown blotches" in absolute terms and now Ken also
raises the issue of their resolution.
http://en.wikipedia.org/wiki/Monsoon
Monsoons are caused by the larger amplitude of the seasonal cycle of land
temperature compared to that of nearby oceans. This differential warming
happens because heat in the ocean is mixed vertically through a "mixed layer"
that may be fifty meters deep, through the action of wind and
buoyancy-generated turbulence, whereas the land surface conducts heat slowly,
with the seasonal signal penetrating perhaps a meter or so. Additionally, the
specific heat capacity of liquid water is significantly higher than that of
most materials that make up land. Together, these factors mean that the heat
capacity of the layer participating in the seasonal cycle is much larger over
the oceans than over land, with the consequence that the air over the land
warms faster and reaches a higher temperature than the air over the ocean.[11]
Heating of the air over the land reduces the air's density, creating an area of
low pressure. This produces a wind blowing toward the land, bringing moist
near-surface air from over the ocean. Rainfall is caused by the moist ocean air
being lifted upwards by mountains, surface heating, convergence at the surface,
divergence aloft, or from storm-produced outflows at the surface. However the
lifting occurs, the air cools due to expansion, which in turn produces
condensation.
In winter, the land cools off quickly, but the ocean retains heat longer.
The cold air over the land creates a high pressure area which produces a breeze
from land to ocean.[11] Monsoons are similar to sea and land breezes, a term
usually referring to the localized, diurnal (daily) cycle of circulation near
coastlines, but they are much larger in scale, stronger and seasonal.[12]
----- Original Message ----- From: "Stephen Salter" <s.sal...@ed.ac.uk>
To: <rob...@envsci.rutgers.edu>
Cc: <kcalde...@dge.stanford.edu>; "Andrew Lockley"
<andrew.lock...@gmail.com>; <xbenf...@aol.com>; <j...@cloudworld.co.uk>;
<geoengineering@googlegroups.com>; <brian.laun...@manchester.ac.uk>;
<sam.car...@gmail.com>; <p...@cam.ac.uk>
Sent: Saturday, May 09, 2009 6:43 AM
Subject: [geo] Re: Balancing the pros and cons of geoengineering
Hi All
The attached paper by Zickfeld et al shows, in figure 2, what might
happen to the Indian Monsoon if we do nothing. Cooling the sea relative
to the land should move things in the opposite direction.
Stephen
Emeritus Professor of Engineering Design
School of Engineering and Electronics
University of Edinburgh
Mayfield Road
Edinburgh EH9 3JL
Scotland
tel +44 131 650 5704
fax +44 131 650 5702
Mobile 07795 203 195
s.sal...@ed.ac.uk
http://www.see.ed.ac.uk/~shs
Alan Robock wrote:
Dear Ken,
I agree. We need several models to do the same experiment so we can
see
how robust the ModelE results are. That is why we have proposed to the
IPCC modeling groups to all do the same experiments so we can compare
results. Nevertheless, observations after large volcanic eruptions,
including 1783 Laki and 1991 Pinatubo, show exactly the same precip
reductions as our calculations.
Even if precip in the summer monsoon region goes down, how important
is
it for food production? It will be countered by increased CO2 and
increased diffuse solar radiation, both of which should make plants
grow
more. We need people studying impacts of climate change on
agriculture
to take our scenarios and analyze them.
Alan
Alan Robock, Professor II
Director, Meteorology Undergraduate Program
Associate Director, Center for Environmental Prediction
Department of Environmental Sciences Phone: +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
Ken Caldeira wrote:
A few questions re claims about monsoons:
1. How well is the monsoon represented in the model's base state? Is
this a model whose predictions about the monsoon are to be trusted?
2. Since the believability of climate model results for any small
region based on one model simulation is low, for some reasonably
defined global metrics (e.g., rms error in temperature and precip,
averaged over land surface, cf. Caldeira and Wood 2008) is the
amount
of mean climate change reduced by reasonable aerosol forcing? (I
conjecture yes.)
Alan is interpreting as significant his little brown blotches in the
right side of Fig 7 in a model with 4 x 5 degree resolution (see
attachment).
How does the GISS ModelE do in the monsoon region? If you look at
Fig
9 of Jiandong et al (attached), at least in cloud radiative forcing,
GISS ModelE is one of the worst IPCC AR4 models in the monsoon
region.
So, while Alan may ultimately be proven right, it is a little
premature to be implying that we know based on Alan's simulations
how
these aerosol schemes will affect the Indian monsoon.
If you look at Caldeira and Wood (2008), we find that idealized
Arctic
solar reduction plus CO2, on average precipitation is increased
relative to the 1xCO2 world.
___________________________________________________
Ken Caldeira
Carnegie Institution Dept of Global Ecology
260 Panama Street, Stanford, CA 94305 USA
kcalde...@ciw.edu <mailto:kcalde...@ciw.edu>; kcalde...@stanford.edu
<mailto:kcalde...@stanford.edu>
http://dge.stanford.edu/DGE/CIWDGE/labs/caldeiralab
+1 650 704 7212; fax: +1 650 462 5968
>
--
The University of Edinburgh is a charitable body, registered in
Scotland, with registration number SC005336.
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