The IPCC's Fragile "Consensus":

Today the Intergovernmental Panel on Climate Change released the "Summary for Policymakers" of the first volume of its Fourth Assessment report on the science of climate change, focusing on the causes, human contribtions, and future projections of climate change. The New York Times covers the release here. The underlying report itself will be published by Cambridge University Press, but an outline is available here.

The Summary for Policymakers provides a layperson friendly summary of the scientific report itself. As such, it typically lacks the nuance, qualifying language, and scientific precision of the underlying study. Indeed, as the IPCC notes, the Summary for Policymakers is drafted by a handful of contributors to the underlying report, and then reviewed and revised by representatives of participating governments before its ultimate publication. (See the NYT's account of this process here.) For this reason there is often some controversy over how the summary document represents some of the more contentious or uncertain issues addressed in the report itself.

In a related vein, yesterday's New York Times reported that the new IPCC report is receiving criticism from some unexpected quarters. In the past, it was climate skeptics who challenged the IPCC's conclusions, and questioned over-reliance upon a purported scientific "consensus." As a result, they labeled "extreme" and "out of the mainstream" for challenging the official "consensus."

Now, however, some of those with more apocalyptic views of climate change are challenging the consensus report (even before it was released) complaining that the IPCC is not alarmist enough. In particular, they object to the lowering of worst-case projections of potential sea-level rise in the new report. (See, e.g., here.) There is also a brewing controversy about how the IPCC characterizes the potential link between global warming and hurricane intensity, reported by Roger Pielke Jr. (see also here) and Chris Mooney. Time will tell what effect these disputes have on the IPCC's effort to do climate science by consensus.