National Academy Report affirms hockey stick: late 20th century temperatures were unprecendentedThis should finally put an official end to the silliness that's gone on for the last few years. I don't doubt that McIntyre will continue to bloviate, but journalists especially now have no reason to give him any traction. (Of course, you knew that four years ago if you were reading this blog.) Just as you no longer hear about the tropospheric temperature question, the hockey stick debate will fade away and everyone can take it and move on to what do we do about it. In particular, maybe the Congressional obstructionists who have dragged this work through the mud will finally move on--mostly because it doesn't really matter if the world is currently warmer than it was 1000 years ago; what matters most is what 380+ ppm CO2 does to our planet today.
The National Academy of Sciences released their report today, on “Surface Temperature Reconstructions for the Last 2,000 Years”. This was requested by Rep. Sherwood Boehlert (Rep., N.Y.) to clarify the controversy over the so-called “hockey stick” temperature reconstructions of the last 1000 years, by Michael Mann (Penn State University), Raymond Bradley (University of Massachusetts) and Malcolm Hughes (University of Arizona). These scientists concluded that the late 20th century warmth in the Northern Hemisphere was unprecedented during at least the last 1,000 years. This drew the ire of Sen. James Inhofe (Rep., Oklahoma) and Rep. Joe Barton (Rep., Texas), who claimed the research was misleading.
The NAS report concluded that, the Mann et al study “has subsequently been supported by an array of evidence”. They find it plausible that “the northern hemisphere was warmer during the last few decades of the twentieth century than during any comparable period over the preceding millennium”. They note that confidence in the record decreases back in time, especially before A.D. 1600, in agreement with the original conclusions reached by the University researchers. The Academy panel also concluded that, “Surface temperature reconstructions for periods prior to the industrial era are only one of multiple lines of evidence supporting the conclusion that climatic warming is occurring in response to human activities, and they are not the primary evidence.”
UPDATE: The National Academy of Sciences is holding a press conference at 8 am PDT, which you can listen to here. Here's their press release:
"High Confidence" That Planet Is Warmest in 400 Years;They did say Mann et al should have made his data more widely available, but did not harp on it, and deferred when asked about it in the question session. Perhaps the wisest words from the press conference were said by Kurt Cuffey: "Science works over time as a community process."
Less Confidence in Temperature Reconstructions Prior to 1600.
There is sufficient evidence from tree rings, boreholes, retreating glaciers, and other "proxies" of past surface temperatures to say with a high level of confidence that the last few decades of the 20th century were warmer than any comparable period in the last 400 years, according to a new report from the National Research Council. Less confidence can be placed in proxy-based reconstructions of surface temperatures for A.D. 900 to 1600, said the committee that wrote the report, although the available proxy evidence does indicate that many locations were warmer during the past 25 years than during any other 25-year period since 900. Very little confidence can be placed in statements about average global surface temperatures prior to A.D. 900 because the proxy data for that time frame are sparse, the committee added.
UPDATE: RealClimate comments here.
It is probably expecting too much for one report might to put to rest all the outstanding issues in a still-developing field. And given the considerable length of the report, we have little doubt that keen contrarians will be able to mine the report for skeptical-sounding sentences and cherry-pick the findings. However, it is the big picture conclusions that have the most relevance for the lay public and policymakers, and it is re-assuring (and unsurprising) to see that the panel has found reason to support the key mainstream findings of past research, including points that we have highlighted previously.