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 7212 [email protected] http://dge.stanford.edu/labs/caldeiralab @kencaldeira *Caldeira Lab is hiring postdoctoral researchers.* *http://dge.stanford.edu/labs/caldeiralab/Caldeira_employment.html* -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en.
