NAS report on "Surface Temperature Reconstructions for the Last 2000 Years"

http://www.sepp.org/weekwas/2006/July%201.htm

Comments by Allan Macrae, 25 Jun 2006

The June 22, 2006 NAS report on climate reconstruction is a fairly reasonable technical document, although it is less than up-to-date and less than competent in some subjects. Regrettably, the Summary and press release are somewhat inconsistent with the Report and exhibit some bias; and the June 22 verbal comments of the panel exhibited strong pro-AGW bias by some members and should be ignored as not representative of the committee report.

For example, the Report upheld virtually all the technical criticisms of Mann's hockey stick (MBH 98 and related papers) by McIntyre and McKitrick (M&M), but some of the panel members went so far in their verbal comments as saying the M&M criticisms were not material - in this regard the committee's verbal comments were hogwash, or more accurately, whitewash.

In truth, Mann's hockey stick eliminated both the Little Ice Age and the Medieval Warm Period from the historic climate record. The NAS committee report confirmed the existence of both these climatic periods, but somehow managed to ignore this important point with respect to Mann's conclusions. Furthermore, the committee blamed the IPCC and the press for overemphasizing the impact of Mann's hockey stick on the global warming debate, ignoring the fact that Mann was a lead author in the IPCC report, who promulgated such overemphasis, and also that Mann's supporting website realclimate further promoted such overemphasis of his flawed conclusions. 

Finally, the committee failed to comment on Mann's reluctance to provide his data for confirmation by others and Mann's refusal to provide full disclosure of his analytical methods. These acts have been condemned by other scientists in the strongest possible terms. some panel members also felt the need to say that the modern warming was clearly human-made, but the committee report provided no evidence to back up this claim. such statements should be deemed unsupported unless evidence is provided. 

Some of my criticisms of the NAS report are its failure to address the following important issues: There are legitimate questions about the accuracy of the surface temperature database. much of the current alleged warming is based on few thermometric measurements in the polar regions from Russia and Canada. however, the USA's NOAA data set, which is likely the very best quality database in the world, shows slight summer and fall cooling in the USA from 1930 to 2005, and about 0.5 C warming only in winter and spring seasons; see http://www.ncdc.noaa.gov/oa/climate/research/cag3/na.html

The committee failed to recognize that the alleged rise in surface temperatures as measured by thermometry is inconsistent with the satellite/balloon records, which showed little or no net warming in the lower troposphere (LT) from 1980 to 2000 (including the 1998 El Nino spike which quickly reversed itself). 

Attribution of recent warming to human-made CO2 ignores the effect of solar variation on cosmic rays and the resulting changes in low-level clouds. the net impact: A stronger sun is amplified by the cosmic- ray effect, and a weaker sun causes even more cooling due to the same cosmic- ray effect . see Veizer and Shaviv (2003) and Veizer (2005) http://www.gsajournals.org/pdfserv/10.1130%2f1052-5173(2003)013%3c0004:cdopc%3e2.0.co%3b2
http://www.gac.ca/journals/gacv32no1veizer.pdf

The committee failed to recognize that NASA stated in their long-range solar forecast issued May 10, 2006: "Solar cycle 25 peaking around 2022 could be one of the weakest in centuries." http://science.NASa.gov/headlines/y2006/10may_longrange.htm?list3134
I believe that this cooling will be much larger than the warming trends observed to date and could have significant negative impacts on Canada, the northern USA and Europe, particularly our agricultural sectors. 

[please note that I predicted that global cooling would start about 2020-2030, in my September 1, 2002 article in the Calgary Herald (based on discussions with Dr. Tim Patterson, paleoclimatologist, of Carleton University).]

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Comments by SFS

The Hockeystick of MBH98 made two claims, adopted also in the Summary of the IPCC-TAR report (2001): 

1) In the past 1000 years, temperatures declined smoothly (until about 1850) showing no significant natural variations, such as the Little Ice Age and the Medieval Warm Period (around 1000 AD).

2) Further, proxies showed higher temperatures in the 20th century than around 1000 AD.

The NAS report contradicts both of these claims. One needs to look only at the key graph of NAS Report in Brief at http://dels.nas.edu/dels/rpt_briefs/Surface_Temps_final.pdf
[For the full report, see http://darwin.nap.edu/books/0309102251/html]

Look only at the four curves based on conventional proxy data; stripping away the curves based on bore holes, glaciers, and instruments -- and compare with the IPCC Hockeystick graph.

In addition, Greenland ice-core data of Dahl-Jensen (direct thermometer measurements in ice boreholes) and of Cuffey (based on oxygen-18 data) show warmer temperatures around 1000 AD than today. Unfortunately, no such data are published for the rest of the globe; but if the cause of these century-scale climate variations is solar, then a global effect is at least plausible.