[The following is an excerpt republished from Andrew Revkin’s Dot Earth Blog of the New York Times – January 19, 2010 (For Revkin’s full post see here.) ]
Revkin Excerpt: The [UN IPCC’s] report on impacts of climate change – one of three main sections of each of the panel’s periodic assessments — has long been seen by some climate scientists, including some participants in the I.P.C.C. process, as a relatively weak element in the overall effort, in part because it has less scientific literature to draw on.
The passage on the Asian glaciers is not alone in including internal inconsistencies or imprecision. The sections on the risks of extinction from warming in the report and the panel’s summaries are, at the very least, confusing.
In the Summary for Policy Makers of the report on climate impacts, there are different summations of extinction risk within a few pages. On page 6, the summary states:
Approximately 20 to 30 percent of plant and animal species assessed so far are likely to be at increased risk of extinction if increases in global average temperature exceed 1.5 to 2.5°C. * N [4.4, T4.1]
In a chart on page 16, at a point marking a 2°C warming from the global average temperature through the 1980s and 1990s, a label reads:
Up to 30 percent of species at increasing risk of extinction.
In the Summary for Policy Makers of the final Synthesis Report drawing on the entire 2007 assessment, the extinction risk is summarized in yet another way (the italics are from the report):
There is medium confidence that approximately 20 to 30 percent of species assessed so far are likely to be at increased risk of extinction if increases in global average warming exceed 1.5 to 2.5°C (relative to 1980 to 1999).
I asked a half dozen I.P.C.C. scientists about this during a side session at the Copenhagen climate talks and, in particular, asked them to decipher for me the meaning of the nested qualifiers in that final statement. Among other things, how much would extinction risk rise? Basically, they acknowledged there was inconsistency and flawed writing.
For Revkin’s complete Dot Earth Blog post see here.