This makes perfect sense, but albedo enhancement can still be useful in:
1. cooling overheating cities, improving local environment and cutting
electricity usage for a/c.
2. producing local cooling where most important, eg in the polar
regions. Just as dark particles (soot / black carbon) are making warming
worse in the Arctic, so whitening surfaces (getting rid of the soot for
a start) will reduce that warming.
Oliver.
On 16/01/2013 19:00, Ken Caldeira wrote:
Folks,
To offset the global mean temperature response to a doubling of
atmospheric CO2 content, you need to deflect back to space about 2% of
sunlight reaching the Earth.
This is often a hard number to get your head around.
Well, it turns out that the area of the US is almost 10 million km2
whereas the area of the world is a little over 500 million km2, so the
US land area is about 2% of Earth's surface area, so we are talking
about deflecting sunlight away from Earth over an area approximately
equivalent to the area of the United States.
This indicates why land surface albedo approaches have difficulty. If
you can change surface albedo an average of 0.1 (when viewed from
space through clouds etc), then you would need to change the albedo by
this amount over an area equivalent to 10 times the area of the United
States to offset a doubling of atmospheric CO2 content.
Incidentally, the area of the continent of Europe is slightly over 10
million km2, so this analogy works for Europe also. (Note that the
area of the European Union is less than half the total area of the
European continent. There is a lot of Russia in Europe.)
Best,
Ken
PS. I encourage you to watch an interview with me yesterday on Current
TV related to the Keystone XL pipeline:
http://current.com/shows/the-young-turks/videos/climate-scientist-if-obama-approves-keystone-xl-his-legacy-will-be-shameful
_______________
Ken Caldeira
Carnegie Institution for Science
Dept of Global Ecology
260 Panama Street, Stanford, CA 94305 USA
+1 650 704 [email protected]
<mailto:[email protected]>
http://dge.stanford.edu/labs/caldeiralab@kencaldeira
*Caldeira Lab is hiring postdoctoral researchers.*
*http://dge.stanford.edu/labs/caldeiralab/Caldeira_employment.html*
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