fun fact: area of USA (or Europe) is about 2% of planetary area

[Ken Caldeira]

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 kcal...@carnegiescience.edu

http://dge.stanford.edu/labs/caldeiralab  @kencaldeira

Caldeira Lab is hiring postdoctoral researchers.

http://dge.stanford.edu/labs/caldeiralab/Caldeira_employment.html

[Oliver Tickell]

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.

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[Andrew Lockley]

Oliver,

Pls note recent posts of papers on this list that shows urban albedo projects can increase AC use by reflecting light into windows and onto walls.

Please further note the study that suggests urban albedo can cause atmospheric effects which lead to urban heat island exacerbation.

I'll look up the papers if anyone needs them.

A

[David Lewis]

re:  Ken's statement on Keystone XL. 

The idea that the US can stop or even slow the development of the tar sand deposit by Obama refusing to grant Keystone XL a permit is questionable.  

Canadian national policy is to develop the tar sands.  Several pipeline projects are in the works that will allow the oil that would have flowed through Keystone XL to cross British Columbia instead so it can be sold from Canada's Pacific ocean ports. (see:  Northern Gateway pipeline.   see also:  Kinder Morgan  pipeline.)    If it comes to it, and somehow, no pipeline can be built, there is a proposal going forward to move 5 million or more bpd by rail across existing rights of way from Alberta to the port of Valdez, Alaska. 

Obama is presiding over a US that is expanding its own oil production at a dramatic rate - Bloomberg Businessweek reports the US expanded its oil production this year  [ 2012 ]  "the most since the first commercial well was drilled in 1859", i.e. by 766,000 barrels per day.  Pretending that Obama can create some kind of climate legacy by putting up a roadblock to Canadian oil development that the Canadians can unblock while developing the considerable US oil and other fossil fuel resources at breakneck speed is preposterous, and it will appear so to our descendants.  

The US international negotiating position on limiting carbon dioxide emission to the atmosphere is predicated on ignoring scientific advice that rapid decarbonization of civilization is necessary.  

Canada is following where the US is leading on this issue.  The Canadian position on Kyoto was to sign, because it thought the US was signing, except Canada took on a slightly more ambitious target for CO2 reduction that what the US was prepared to do.  When it dawned on Canadians that Kyoto was not going to be approved by the US Senate, they abandoned any effort to live up to the agreement they signed, and eventually Canada became the first country to repudiate their Kyoto signature.  The basic fact is that 85% of Canadian trade is with the US - the country can't see implementing significantly different policy on such a major issue than its major trading partner.