CAS People

Kevin Trenberth, Distinguished Senior Scientist

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

Statement on Landsea Affair

"The global warming influence provides a new background level that increases the risk of future enhancements in hurricane activity.", Kevin Trenberth


The vigorous hurricane season in the Atlantic in 2004, where 4 hurricanes hit Florida and flooding occurred along much of the eastern seaboard, attracted widespread media attention. Comments by a few scientists, including Landsea, suggested that there was no relation between these events and global warming. On October 14, 2004, a press conference called by the Harvard Medical School Center for Health and the Global Environment was held by teleconference with about 40 reporters to correct that impression and recognize that global warming is happening and hurricanes cannot be unaffected. Landsea took offense at Trenberth's participation in the news conference and what Trenberth said. Landsea issued a public letter on January 14, 2005 in which Landsea resigned from the IPCC but also made a number of charges that are not correct. There was considerable publicity about Landsea's letter, such as Trenberth and UCAR (Trenberth's employer) disputed Landsea's comments and UCAR posted the news release and NCAR Statement associated with Trenberth's comments online to show that several misquotes had been made.

Chris Landsea was not a Coordinating Lead Author (CLA) or a Lead author of the IPCC report. Landsea was asked by the CLAs to be a contributing author (there are 66 in Chapter 3) who write a half page or so on a particular topics that are assembled into the report by the Lead Authors. Landsea could easily refuse to do so, but to publicly resign the way Landsea did was a very political approach that had nothing to do with any scientific dispute. Actually one can't resign from something that one is not a member of!

Trenberth's response was to publish the scientific basis for the news conference criticized by Landsea in the June 2005 Science. Kerry Emanuel of the Massachusetts Institute of Technology independently published direct observational evidence in Nature only two months later. Emanuel showed that significant increases in cyclone intensity and duration around the world since 1970 have been strongly related to rising SSTs. Challenges from Landsea and other experts to Emanuel's work led to modest revisions in the specific correlations (PDF), Emanuel 2005b, but do not alter the overall conclusion. In September 2005 Peter Webster and his colleagues at the Georgia Institute of Technology published an article in Science that explicitly showed a substantial rise in the number of Category 4 and 5 hurricanes since 1970 and in the percent of total hurricanes that fit that description. Webster and colleagues concluded that the rise was to be expected, given the observed increase in SSTs. Trenberth and Shea subsequently published an analysis of the role of global warming in hurricanes. [Hurricanes News Release]

Landsea's letter was written late in 2004, and subsequently, in addition to the many new published papers, the record breaking 2005 hurricane season occurred, including hurricane Katrina and 3 other category 5 hurricanes.

There is no doubt that there is large natural variability in hurricanes, and also disputes about how reliable the record is, points made by Landsea for example, Landsea 2005, Nature,, and Chan 2006, Science,; but other articles have demonstrated that the changes in the hurricane environment have a human component such as Santer et al 2006, Proceedings of the National Academy of Sciences,

There is a wide range of scientific opinion on the issue, reflecting the genuine scientific uncertainties and developing nature of the science. Subsequently, the IPCC has also weighed in and the attribution of changes to a human role are clearly stated in chapters that were not authored by Trenberth.

As to Trenberth's credentials with regard to the issue, while it was true that Trenberth had not, in 2004, published articles on hurricanes as such, Trenberth had extensively published on changes in water vapor, precipitation, storms, and the hydrological cycle, and there is no doubt that hurricanes are a subset of storms. Subsequently Trenberth has published several articles on hurricanes and, along with other research, there is exceedingly strong support for the comments made in the news conference. On the other hand, there is no basis for Landsea's position.

Related Articles

  • Trenberth, K. E., 2005: Uncertainty in Hurricanes and Global Warming. Science, 308, 1753-1754. [summary] [paper]
  • Trenberth, K. E., and D. J. Shea (2006), Atlantic hurricanes and natural variability in 2005, Geophys. Res. Lttrs., 33, L12704, doi:10.1029/2006GL026894. [paper]
  • Trenberth, K. E., C. A. Davis and J. Fasullo, 2007: Water and energy budgets of hurricanes: Case studies of Ivan and Katrina . J. Geophys. Res., 112, D23106, doi:10.1029/2006JD008303. [paper]
  • Trenberth, K. E., and J. Fasullo, 2007: Water and energy budgets of hurricanes and implications for climate change. J. Geophys. Res., 112, D23107, doi:10.1029/2006JD008304. [paper]
  • Trenberth, K. E., and J. Fasullo, 2008: The energy budgets of Atlantic hurricanes and changes from 1970. Geochemistry, Geophysics, Geosystems, 9, doi:10.1029/2007GC001847. [paper]

CGD People

Kevin Trenberth

CGD Distinguished Senior Scientist

Phone: 303.497.1318
Email: trenbert(at)

04' Hurricane Season

10/14/04: Press Release

10/21/04: News Conference to correct misquotes of10/14/04 Press Release

11/08/04: Trenberth replies

01/14/05: Landsea resigns

01/28/05: UCAR/NCAR Statement

Trenberth publishes "Uncertainty in Hurricanes and Gobal Warming", 2005 Science

Pielke and Landsea publish"Hurricanes and Global Warming",2005, BAMS

Rebuttal of Pielke and Landsea articleby news conference participants

'05 Hurricane Season Record Year

Anthes et al response to Pielke and Landsea article, May 2006, BAMS

Pielke and Landsea, reply to Anthesarticle, May 2006, BAMS

January 2007: AR4 IPPC