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Author: AstroPhool Three stars, 500 posts Old School Fool Add to my Favorite Fools Ignore this person (you won't see their posts anymore) Number: of 54209  
Subject: Re: New Hansen Study Date: 9/17/2013 8:48 PM
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The latest Hansen paper is an important study (which I already mentioned on this board in post 44893):
http://boards.fool.com/reason-52321-that-climate-change-rese...
The link below (to arXiv) is freely available (no paywall).


DB2: Do you have some links to papers?

Most of the supporting paleoclimate evidence can be found in Hansen's (2013) paper: Climate Sensitivity, Sea Level, and Atmospheric CO2: http://arxiv.org/abs/1211.4846


Apart from his value of the climate sensitivity (3-4 C):
Glacial-to-interglacial climate change leading to the prior (Eemian) interglacial ... implies a sensitivity...[of] 3–4°C for a 4?W?m-2 CO2 forcing...


Also: "We hypothesize that the global climate variations on the Cenozoic can be understood and analyzed via slow temporal changes of Earth's energy balance, which is a function of solar irradiance, atmospheric composition (specfically long-lived GHGs), and planetary surface albedo."

From these assumptions, Hansen is able to reproduce the temperature variations seen in the Antarctic ice core record based on just 3 forcings: orbital, greenhouse gases and albedo. From this analysis, Hansen derives a fast-feedback climate sensitivity of 3-4 C, that does not include albedo changes due ice sheet growth or decay. When the albedo changes are considered to be a consequence of changing CO2 concentrations, then the long-term climate sensitivity from the ice core record is about 10 C. Hansen must recover this value also (although he doesn't quote it as such) because he is able to reproduce the ice core temperature record.

When looking at the long-term response (centuries to millenia, as needed for sea level rise estimates) it is the 10 C sensitivity that is more useful, because that value implicitly includes the changes in albedo due to decreased ice sheet coverage from greenhouse warming.

Overall, this paper is a sobering read. Especially his conclusions:
"Burning all fossil fuels would produce a different, practically uninhabitable, planet."


Phil
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