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SW: →Historical temperature reconstructions: Add section on NRC
"The TAR pointed to the ‘exceptional warmth of the late 20th century, relative to the past 1,000 years’. Subsequent evidence has strengthened this conclusion. It is very likely that average Northern Hemisphere temperatures during the second half of the 20th century were higher than for any other 50-year period in the last 500 years. It is also likely that this 50-year period was the warmest Northern Hemisphere period in the last 1.3 kyr, and that this warmth was more widespread than during any other 50-year period in the last 1.3 kyr." [AR4 6 ES]
====NRC report====
In 2006, following a request from the U.S. Congress, the National Research Council issued a report entitled [http://books.nap.edu/openbook.php?record_id=11676&page=R1 "Surface Temperature Reconstructions for the Last 2,000 Years"] (NRC). In a "Supplementary Information" section, the ISPM contends: "The National Research Council recommended that proxies sensitive to precipitation be avoided in temperature reconstructions and, in particular, that strip-bark bristlecones and foxtails be avoided." [ISPM 3.2a].
However, this would appear to be an imprecise summary of the NRC recommendations. The NRC stated that "[U]sing proxies sensitive to hydrologic variables ... should be done only if the proxy–temperature relationship has climatologic justification." (NRC, p. 116-7) It should be clarified as well that the NRC did not recommend against the use bristlecones and foxtails as proxies, but rather stated that "'''strip-bark samples'''" of these proxies should be avoided [emphasus added].
The ISPM goes on: "However, none of the IPCC reconstructions for the past millennium observe the National Research Council recommendations."
==External links==
