Pros and Cons of SRM geoengineering more widely
John Nissen
Hi all,
Recently the geoengineering group discussed the pros and cons of solar
radiation management (aka SRM geoengineering) using stratospheric
aerosols in the Arctic [1].
A possible downside of more widespread deployment of stratospheric
aerosols has come to light; it is from decreased rainfall on Amazon
[2]. Some of us were already concerned by possible slight weakening of
monsoons.
This decreased rainfall is liable to be aggravated by the growing El
Nino. (The last strong one was in 1998.)
Yet some experts (e.g. Jeff Ridley) are saying that deployment in the
Arctic will not be sufficient to save the sea ice. (And if the sea ice
goes, the methane could come out of permafrost, Greenland ice sheet
disintegrate, etc.)
And Alan Gadain, from the University of Leeds was warning me, last week
[3], that Arctic deployment wouldn't work, yet on the other hand an
effect of more general deployment would be to cool the Arctic.
Who is right, and what should we do?
Could there be a way to protect Amazon and elsewhere from reduced
rainfall, while deploying stratospheric aerosols at a range of latitudes
to produce both widespread cooling effect and specific cooling in the
Arctic?
We could use marine cloud brightening rather than stratospheric
aerosols, because the risk of undesirable side effects is smaller and
because the technique can be applied locally, but do we have the luxury
of time to develop the technique? The Arctic sea ice is liable to
disappear more rapidly than anyone expected - we just cannot predict
with any certainty. Likewise the Amazon rainforest could perish if
there were consecutive years of drought - which we cannot predict.
Isn't there an overwhelming case for some kind of experimental trial of
stratospheric aerosols in the Arctic, preferably starting next spring,
before El Nino effects set in? There is so much at stake, wouldn't it
be stupid to delay?
And shouldn't some significant funding be put into marine cloud brightening?
Cheers from Chiswick,
John
[1] "Balancing the pros and cons of geoengineering" thread:
http://groups.google.com/group/geoengineering/browse_thread/thread/b045b6428fc89a93/95b940c3c3352e35?#95b940c3c3352e35
[2] Aerosol effects investigated by Met Office:
http://www.metoffice.gov.uk/corporate/pressoffice/2009/pr20090604.html
[3] Geoengineering seminar at the House of Commons, 15th July 2009.
John Latham
As JohnN says, marine cloud brightening is, in principle, a viable, quantitatively adequate alternative to stratospheric seeding, and I think that possibility should definitely be looked into.
However, Ken Caldeira has suggested an interesting variation, which is that these two geoengineering schemes could perhaps be deployed in concert, the stratospheric scheme providing a general cooling, and the cloud brightening technique providing localised fine tuning, which is possible because not all clouds need to be seeded, and judicious choices as to where to cool can therefore be made. Such a combination (or perhaps cloud brightening alone) could, for the above reasons, possibly ameliorate or eliminate the Amazonian problem.
I should add that fully-coupled atomosphere/ocean GCM computations by Phil Rasch and Jack Chen, indicate that the cloud brightening scheme produces its maximum cooling in the Polar regions.
Cheers, John.
--
John Latham
lat...@ucar.edu & john.l...@manchester.ac.uk
Tel. 303-444-2429 (H) & 303-497-8182 (W)
Andrew Lockley
Alan Gadian
John,
A quick note. I hope I was saying that, if you believe the
models which seem OK for temperatures, the sulphur scheme
would cool the poles, and the rest of the planet more.
Both Rasch's results and those of Lund (bristol) showed this.
However, the cooling associated with the cloud whitening scheme,
is especially pronounced at the pole (as shown by Rasch and our HaDGAM
results) and therefore could help preserve the permafrost.
I am afraid I have little faith in the precipitation from climate
models, especially in the tropics. Parts of India have predictive errors
of over 2m per year for current simulations. With doubling CO2
there will be precipitation shifts, definitely. Cloud whitening is likely
to have them too, but hopefully will counterbalance the increasing CO2
shifts.
I think it is important not to jump in too soon, but examine with models
and small experiments the viability of schemes. I appreciate that
some (well Steven Rayner) at the meeting called me a "climate porn
merchant" ... and many other "jibes" , and I was also called a
"scaremongerer", but I feel it would be of advantage to take as many
people forward as possible, and explore all the facets of each approach.
NERC and EPSRC are preparing initiatives, and I do agree it is
urgent. There may ( or may not) be ozone depletion problems with
significant use of sulphates, so we must take care.
Cheers
Alan
Stephen Salter
The Met. Office statement at
http://www.metoffice.gov.uk/corporate/pressoffice/2009/pr20090604.html
did not mention that the Jones Haywood Boucher results were based on
treating just 3.3 % of the earth's surface. One of the the areas
treated in the South Pacific off Chile and Peru. It would be
interesting to know if treating the other side of the Pacific would
produce the opposite effect and if a judicious balance between the two
could achieve any desired beneficial result. It was unfortunate that
this was not done. Perhaps it soon will be.
Because of the log term in the Twomey effect we get much better cooling
for a given spraying effort with a lower dose over a large area than
with the high local concentration used in their paper. While it may be
scientifically interesting to model an extreme case it would not have
been possible to confine the spray to such an extent. Even so, the
predicted cooling for treating the small area was equivalent to the
cancellation of all damage since pre-industrial times.
The Met. Office statement did not mention the prediction by Jones et al.
of increased precipitation in drought-stricken regions of sub-Saharan
Africa, northern India and eastern Australia.
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.Sa...@ed.ac.uk
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Scotland, with registration number SC005336.
John Gorman
I hope I said how strongly some of us agree with your "alarmism". The
possible or probable future without geoengineering is alarming!! It reminds
me of the quote from the old Englishman Rudyard Kippling -"If you can keep
your head when all about you are loosing theirs, could it be that you havn't
understood the situation?"
I also agree that a combination of cloud whitening and aerosols, both being
carefully placed should be able to control temperature while we sort out
some methods of getting CO2 levels back to preindustrial. Difficult but we
have got to do it. A whole new science.
John Gorman
Alan Gadian
John,
Yes: I do think that we are in a critical situtation, and although
alarmist, there has been progress in the way the whole subject has been
taken much more seriously, even since Xmas.
Thanks for your support ... rather apt, because the Indian sub continent
is where may be the biggest effects may be felt
Alan
John Nissen
Dear Alan,
Thank goodness some people are beginning to take matters seriously. It
has also become clear to some of us that emissions reduction, however
drastic and however widespread, would have little chance by itself to
prevent a global catastrophe. The Arctic sea ice has seemed the most
critical thing to save, but there is also the West Antarctic ice sheet
(WAIS), the Amazon rainforest and the Himalayan glaciers, while the
combination of global warming and ocean acidification is threatening
coral reefs and ultimately the whole marine food chain. Thus
geoengineering has become absolutely necessary; and it is now a matter
of extreme urgency, since we are battling against growing positive
feedback and unpredictable effects.
A number of us have put our names to an open letter to Dr Pachauri,
delivered to him at the Copenhagen Climate Congress in March [1].
However, as yet we have not received a response. I still think that his
acknowledgement of the need for geoengineering (here including carbon
stock management processes such as biochar) would have a big impact in
advance of the Copenhagen meeting in December. Would you be willing to
add your name, and support a second approach to Dr Pachauri? I think we
should extend our proposal to include SRM geoengineering more widely
(i.e. not just to save the Arctic sea ice).
What would be the best timing? Could we make an announcement on the
occasion of, or immediately following, the public release of the Royal
Society's report - which is due 1st September? We might also enlist
some people who worked on the report.
Best wishes,
John Nissen
[1]
http://geo-engineering.blogspot.com/2009/03/open-letter-to-dr-pachauri.html
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