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‹and quite possibly sea salt
CCN--emitted above the inversion is likely 10 days or so. It is not at all
clear to me that the 6 to 1 or so lifetime advantage of the lower
stratosphere is really worth the effort to loft the aerosols.
And on the temperature rise in the polar stratosphere, I would hope any
calculation of the effects of the sulfate/dust injection only put it in
during the sunlit season‹obviously, there would be no effect on solar
radiation during the polar night, so, with a two month lifetime of aerosols
there, it makes absolutely no sense to be lofting anything for about two
thirds of the year. And so likely no effect on winter temperatures (although
warming the coldest part of the polar winter stratosphere might well help to
prevent an ozone hole from forming).
So, I think a tropospheric brightening approach is likely the better option.
Whether it can be done with just CCN or might also need sulfate seems to me
worth investigating (what one needs may well be not just cloud brightening,
but also clear sky aerosol loading).
Best, Mike
*****
On 3/17/12 8:41 PM, "Ken Caldeira" <[email protected]> wrote:
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 Global Ecology
260 Panama Street, Stanford, CA 94305 USA
+1 650 704 7212 [email protected]
http://dge.stanford.edu/labs/caldeiralab @kencaldeira
YouTube:
<http://www.youtube.com/watch?v=a9LaYCbYCxo> Climate change and the
transition from coal to low-carbon electricity
<http://www.youtube.com/watch?v=a9LaYCbYCxo>
Crop yields in a geoengineered climate
<http://www.youtube.com/watch?v=-0LCXNoIu-c>
On Sat, Mar 17, 2012 at 1:31 PM, Andrew Lockley <[email protected]>
wrote:
Hi
Here are some model outputs which Stephen sent me. These appear to show
localized arctic warming in geoengineering simulations. This could be due to
winter effects.
I assume this is the source for the controversial figure in the BBC quote
A
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