July 6, 2010


Accentuate the negative (The Economist, Jul 5th 2010)

FOR everyone else it was the glaciers: for the Dutch it was the flooding. Last January errors in the work of the Intergovernmental Panel on Climate Change (IPCC) hit the headlines. The chapter on Asia in the report by the IPCC’s second working group, charged with looking at the impact of climate change and adapting to it, mistakenly claimed that the Himalayan glaciers would be gone by 2035. This contradicted some reasonably basic physics, had not been predicted by the glacier specialists in the first working group (which deals with the natural science of past and future climate change) and was unsupported by any evidence. There was a report from the 1990s which said something similar about all the world’s non-polar glaciers, but it gave the date as 2350. Then there was a crucial typo and some shoddy referencing. Nevertheless the IPCC’s chair, Rajendra Pachauri, had lashed out at people bringing the criticism up, accusing them of “voodoo science”. He then had to eat his words, and set up, with Ban Ki-moon, a panel to look into ways the IPCC might be improved.

Inspired by this to look for other errors, a journalist for a Dutch newspaper spotted that the chapter on Europe gave a figure for the area of the Netherlands below sea level that was much too large. The area at risk of flooding by the sea had been conflated with that at risk of flooding by the Rhine and the Meuse rivers. That the careful Dutch should have provided faulty information and not spotted it in the review process was an embarrassment to the then environment minister, Jacqueline Cramer; following a debate in parliament she called on the Netherlands Environmental Assessment Agency (PBL), an independent body, to look at all the regional chapters in the working group II report and make sure they were up to snuff. This the PBL has now done; its report was published on July 5th.

The authors try hard to make clear that their findings do not undermine the IPCC's conclusions on climate change. And there is nothing in their report as egregious as the glaciers or as embarrassing as the Dutch sea level. But they did find a number of things to take issue with, most of which they thought minor but eight of which they classed as major; and their work seems to bring out a systemic tendency to stress negative effects over positive ones. This tendency can be defended. But a reading of the report suggests there may also be broader and potentialy more misleading bias. The PBL report chose as its main focus a table in the “Summary for Policy Makers” of the IPCC’s 2007 “Synthesis Report”, which brings together the results of working groups one, two and three (which deals with responses to climate change). Where did these bullet points actually come from, the PBL team asked, and how well supported were they? [...]

Perhaps the most worrying thing about the PBL report, though, is a rather obvious one about which its authors say little. In all ten of the issues that the PBL categorised as major (the original errors on glaciers and Dutch sea level, and the eight others identified in the report), the impression that the reader gets from the IPCC is more strikingly negative than the impression which would have been received if the underlying evidence base had been reflected as the PBL would have wished, with more precise referencing, more narrow interpretation and less authorial judgment.

Posted by Orrin Judd at July 6, 2010 5:29 AM
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