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Is The IPCC Biased? Let's Ask The Dutch.

This week, two more "Climategate"-related investigations trickled out, and—no surprise—both of them knocked down (yet again) the long-running charge that climate scientists are engaged in some sort of massive fraud. Mainstream climatology is still holding up under scrutiny. (Well, either that or the climate conspiracy runs far, far deeper than anyone thought.) But that said, there were a few twists and complications in the two reports, and they're worth looking at in some detail. I'll examine the first one in this post.

On Monday, the Netherlands Environment Agency (PBL) released its review of the IPCC's big climate assessments. This all started because the IPCC's 2007 report had stated that 55 percent of the Netherlands was below sea level; that turned out to be incorrect, and the Dutch government wanted to figure out what went wrong. As it turns out, it was a pretty innocent error. Only 26 percent of the country is below sea-level while another 29 percent is at risk of river flooding. The Dutch government had added these two numbers up and handed the data over to the IPCC, which trusted the numbers. So it was a mistake, yes, but not one made by climate scientists.

The Dutch review found nine other errors in the IPCC report, but they were all quite minor (save for that goof about melting glaciers in the Himalayas). Here's a good example: The IPCC had stated that climate change would put stress on water supplies for 75 million to 250 million people in Africa by 2020; it turns out the numbers should have been 90 million to 220 million. Okay, fine. The IPCC has accepted most of these corrections, but none of them are really an attack on the foundations of climatology, and the Dutch report determined that none of the IPCC's conclusions "were found to contain significant errors."

More interesting, perhaps, is that according to the Dutch government, the IPCC has a tendency to "single out the most important negative impacts of climate change" in its summaries for policymakers. Does this prove climate scientists are too alarmist? Not really. As the Dutch review notes, governments had specifically asked the IPCC to highlight the risks the planet faces from global warming, since, understandably, that's of interest. And the IPCC does highlight positive impacts from climate change in its report—they're just massively outweighed by the negative impacts and tend to get less play in the summary. (Note that this is a separate issue from the argument that the IPCC is also too conservative and cautious on many issues, such as melting ice sheets.)

In any case, the Dutch government suggested that the IPCC give policymakers two summaries: one outlining the range of potential outcomes, and another that focuses on negative impacts and worst-case scenarios. That's not a bad idea, and underscores the fact that climate policy is all about dealing with uncertainty. (For more on this, the CBO of all places put out a good report back in 2005 trying to get a handle on how to make policy under this sort of uncertainty.)