CAS People

Kevin Trenberth, Distinguished Senior Scientist

Statement: Kevin Trenberth on Developments related to Landsea "walking out on IPCC."

Trenberth email response to Landsea, November 8, 2004

Dear all,

I am disappointed that Chris Landsea has decided to politicize this. It is true that there was a conference call press conference on the subject of hurricanes that was set up by Paul Epstein and his colleagues at the Center for Health and the Global Environment in which I participated. Jim McCarthy, Co chair WG II from the IPCC Third Assessment Report (TAR) also participated, and others. I believe there were some 40 to 50 participants from the media. I have seen dozens of news reports resulting from the event. It is hard to know that many of them attended the same event or heard the same material, given how differently it was all reported. So one should NOT base anything on news reports over which I have no control. Here is the statement I released as part of the material distributed.

"Human activities are changing the composition of the atmosphere and global warming is happening as a result", says Kevin Trenberth, Head of the Climate Analysis Section at NCAR and a Convening Lead Author of the 2007 IPCC report for the chapter on observed changes. "Global warming is manifested in unexpected ways. Sea level has risen 1.25 inches in the past 10 years as a result of warming of the oceans and glacier melting. The environment in which hurricanes form is changing. The result was a hurricane in late March 2004 in the South Atlantic, off the coast of Brazil: the first and only such hurricane in that region. Several factors go into forming hurricanes and where they track. But the evidence strongly suggests more intense storms and risk of greater flooding events, so that the North Atlantic hurricane season of 2004 may well be a harbinger of the future."

The news event was spawned, I believe, in large part to correct many very misleading and erroneous reports that global warming had nothing to do with the hurricanes in recent times. Chris Landsea was one person who portrayed them that way, although people like Bill Gray and Jim O'Brien were most quoted. I believe we were cautious in the words we used but at the same time we clearly indicated that the environment in which these storms are forming has been altered by climate change associated with human activities. This follows from the TAR. There are separate reports, such as the one below from the NY Times that are independent [Not enclosed here], based on other relevant literature. Moreover there is plenty of evidence from published literature that rainfall events in the US and elsewhere are becoming more extreme. In Japan, my understanding is that there is widespread acceptance that the hurricanes are related to global warming. However, Chris certainly misquotes some things I did NOT say. I did not say the increase in frequency was related to global warming, on the contrary I explained why this could not be said. I did say that given a tropical storm its intensity is likely to be greater and with greater rainfall given the higher sea surface temperatures and observed increase in surface humidity.

We are keen to get Chris' contribution to the AR4. In fact we seek contributions from disparate scientists who we know do not see eye to eye and the disagreements will be included in the report. Accordingly I urge Chris to send his contribution in: it is already overdue.