“[T]here is no sound theoretical basis for drawing any conclusions about how anthropogenic change affects hurricane numbers or tracks, and thus how many hit land.” K. Trenberth, Science, 17 June 2005

Last winter, Chris Landsea caused a flap when he resigned from the IPCC claiming that Kevin Trenberth, the lead author of the IPCC chapter that he was contributing to, had made unfounded statements about hurricanes and global warming in a press conference organized by Harvard to allege a connection between the U.S. hurricane damages of 2004 and human-caused climate change. (Disclaimer: As most regular readers know, Landsea is a long-time collaborator of mine.) In this week’s Science, Trenberth has an essay on hurricanes and climate change that should put this issue to rest. Trenberth’s essay clearly vindicates Landsea’s actions, and, in my opinion, it would not be inappropriate for IPCC officials who failed to support Landsea (Rajedra Pachauri and Susan Solomon) to issue him a public apology. But don’t hold your breath.

Let’s take a quick look at Trenberth’s essay and explain why it vindicates Landsea.


Trenberth confirms in his Science essay what Landsea has claimed, that — based on what is known today — “there is no sound theoretical basis for drawing any conclusions about how anthropogenic change affects hurricane numbers or tracks, and thus how many hit land.” None. There is no basis for claiming as Trenberth did that the hurricanes of 2004, much less their damages, could be attributed to human emissions of greenhouse gases/global warming. Earlier this year, Trenberth said that his participation in the Harvard press conference was “to correct misleading impressions that global warming had played no role at all in last year’s hurricane season.” It is good to see this claim corrected.

Trenberth confuses the issue by calling into question the role of hypothesis testing in science (one wonders what this apparently new found perspective on hypothesis testing means for the rest of climate science, but I digress), and some discussion of variables that clearly have some effects on hurricanes (i.e., ENSO), but in the end he concludes “it is not yet possible to say how El Nino and other factors affecting hurricane formation may change as the world warms.”

A more comprehensive review of current understandings of hurricanes and global warming can be found in this peer-reviewed paper, forthcoming in the Bulletin of the American Meteorological Society:

Pielke, Jr., R. A., C. Landsea, K. Emanuel, M. Mayfield, J. Laver and R. Pasch, in press. Hurricanes and global warming, Bulletin of the American Meteorological Society. (PDF)

Bottom line: Landsea and Trenberth are scientifically on the same page, and the perspectives now being espoused by Trenberth are (in my interpretation) entirely consistent with what Landsea argued at the time he stepped down from the IPCC. Because of Trenberth’s change in perspective, Landsea should feel completely vindicated. The IPCC should be big enough to note this and invite Landsea back into the fold.

A final note, NCAR’s press release and those who approved it apparently learned little from the controversy as the press release irresponsibly muddies the issue by making it look like there is in fact a clear global warming-hurricane connection and that there is new information in the Trenberth paper. If the Trenberth paper is cited in the media as supporting a hurricane-global warming connection (and we’d welcome any links to media coverage), then I place full responsibility on the unnecessarily obfuscatory NCAR press release which sets the stage for a further mischaracterization of this issue, on which scientists who once differed, now agree. That is the real story.