The October issue of the Bulletin of the American Meteorological Society (BAMS) has an exchange of letters on trends in climate impacts and the attribution of those trends to human-caused climate change. Our letter was prepared in response to a December paper in BAMS by Paul Epstein and John McCarthy (EM04). EM have a reply (PDF) to our letter which I will discuss in detail in a subsequent post. Here is a list of the authors of our letter.

-ROGER A. PIELKE JR. University of Colorado/CIRES, Boulder, Colorado
-SHARDUL AGRAWALA OECD Environmental Directorate, Paris, France
-LAURENS M. BOUWER Institute for Environmental Studies (IVM), Faculty of Earth and Life Sciences, Vrije Universiteit, Amsterdam, Netherlands
-IAN BURTON University of Toronto, Toronto, Ontario, Canada
-STANLEY CHANGNON University of Illinois, Champaign, Illinois
-MICHAEL H. GLANTZ Environmental and Societal Impacts Group, NCAR, Boulder, Colorado
-WILLIAM H. HOOKE Atmospheric Policy Program, AMS, Washington, D.C.
-RICHARD J. T. KLEIN Potsdam Institute for Climate Impact Research (PIK), Potsdam, Germany
-KENNETH KUNKEL Center for Atmospheric Science, Illinois State Water Survey, Champaign, Illinois
-DENNIS MILETI Department of Sociology, University of Colorado, Boulder, Colorado
-DANIEL SAREWITZ Arizona State University, Tempe, Arizona
-EMMA L. TOMPKINS Tyndall Centre for Climate Change Research, School of Environmental Sciences, University of East Anglia, Norwich, United Kingdom
-NICO STEHR Zeppelin University, Friedrichshafen, Germany
-HANS VON STORCH Institute for Coastal Research, GKSS Research Center, Geesthacht, Germany

Here is the opening paragraph of our letter (PDF):

“The December 2004 issue of BAMS contains an article warning of the threats of abrupt climate change (Epstein and McCarthy 2004, hereafter EM04). The article seeks to raise awareness of the risks of an abrupt change in climate related to human influences on the climate system, but, in doing so it repeats a common factual error. Specifically, it identifies the recent growth in economic damages associated with weather and climate events, such as Hurricanes Mitch and Jeanne and tornadoes in the United States, as evidence of trends in extreme events, arguing “the rising costs associated with weather volatility provide another derived indicator of the state of the climate system . . . the economic costs related to more severe and volatile weather deserves mention as an integral indicator of volatility.” Although the attribution of increasing damages to climate changes is but one of many assertions made by EM04, the repetition of this erroneous claim is worth correcting because it is not consistent with current scientific understandings.”

Our concluding paragraph is as follows:

“Concern about the possibility of abrupt climate change, whether human caused or not, is well justified (Alley et al. 2003). However, to connect the economic and other human impacts of disasters that have occurred in recent years and decades to climate changes (human caused or not) is not supported by the robust peer-reviewed literature in this area. Advancing such unsupported connections not only can create inefficiencies in disaster policy (Sarewitz and Pielke 2005), but can also open the door to an “overselling” of climate science and a resulting criticism of advocacy efforts regarding climate change (e.g., von Storch and Stehr 2005). Both science and policy will be better served by aligning the justifications advanced for action with current scientific understandings. Future research may yet reveal a connection between climate change and trends in disaster costs, but at present it is premature to attribute trends in disaster costs to anything other than characteristics of and changes in societal vulnerability.”

Please read the whole letter here (PDF).