I just saw an interesting new paper by Lean and Rind in Geophysical Research Letters . These authors performed a multiple regression analysis to determine the influence of natural (solar activity, volcanoes, ENSO) and anthropogenic (greenhouse gases plus aerosols) factors on the temperature record of the past 100+ years. Looks like a good piece of work.
The "solar activity" and "natural cycles" skeptics will not like the conclusions, though. None of the natural factors comes close to explain the overall warming trend. A citation from the paper:
"None of the natural processes can account for the overall warming trend in global surface temperatures. In the 100 years from 1905 to 2005, the temperature trends produced by all three natural influences are at least an order of magnitude smaller than the observed surface temperature trend reported by IPCC [2007]. According to this analysis, solar forcing contributed negligible long-term warming in the past 25 years and 10% of the warming in the past 100years, not 69% as claimed by Scafetta and West [2008]..."
20 September 2008
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If you don't know how the solar mechanism works how can you possibly identify the change in temperature that is caused?
ReplyDeleteThe change in total solar irradiance is indeed insignificant. But the effect of the solar wind on the density of the atmosphere on the day-side is real. It affects the penetration of UV into the tropical troposphere. This drives temperature change at 200hPa and cirrus cloud cover. This in turn affects the energy flow to high latitudes via ocean currents giving rise to dramatic swings in winter temperatures, about five to six times the temperature change observable in mid and low latitudes in any season.
As interesting was the fact that they don't see much trend at high latitudes, but I think they may have missed that HadCrut does not look at high latitudes. Do you know where there are zonal maps of the HadCrut data
ReplyDeleteif you don't know how the solar mechanism works, that's usually to be considered a point against it and in favor of the well understood carbon dioxide mechanism.
ReplyDelete@Eli: Don't know of any zonal maps. The data are here, and the IRI/LDEO CDL offers a nice tool to view such data (see this example).
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