18th Conference on Applied Climatology


Blame it on climate change!

Robert E. Livezey, NWS Retired, Self-Employed Consultant, Bethesda, MD

The intense political and popular interest in climate change and the availability of research dollars has fostered explosive growth in interdisciplinary studies on current and future impacts of climate change. It is difficult to pick up more than a few successive issues of a wide variety of periodicals, including newspapers, popular magazines, and many organizational news letters/magazines, without encountering a popular account of such a study. In the overwhelming majority of these accounts it is clear that the authors of the impacts studies either did not consult appropriate climate expertise or the advice they received lacked objectivity or critical reasoning.

In the case of future impacts studies, these failures most often take the form of missing, insufficient, or non-critical validation of the models producing climate scenarios for the impacts, at time and space scales relevant to the impacts. There seems to be little understanding of the fact that climate models credibly reproduce weather-making processes at only the grossest of time and space scales, namely seasonal and continental respectively. Consequently, only a special sub-set of such studies have any practical value. I have previously called for a greater emphasis on climate model validation and more transparent assessments of model limitations, so this discussion will focus on studies of current impacts of climate change.

It is quite rare today to encounter an account of an interdisciplinary climate change impacts study that does not conclude that climate change is a major contributing factor to some harmful trend. It is reminiscent of the Winter of 1997-98 when both professionals and non-professionals seemed to blame every high-impact weather event on El Nino. In reviewing these accounts I have encountered three different basic errors, all of which most competent State Climatologists, for example, could have prevented:

(1) Presuming the existence of a warming trend when one does not exist or is inconsequential. Warming to date is unevenly distributed geographically and seasonally and is expected to continue to be so in the future. It is a commonly-held fallacy that summer heat waves are a widespread, growing problem because of climate change.

(2) Presuming cause-effect because of the presence of a warming trend, without supporting evidence of a link and even an instance when relevant evidence suggested otherwise.

(3) Incompetently (specifically over-) estimating the rate of climate change over the last several decades. The most common error is trend fitting in much of the eastern two-thirds of the United States from the mid- to late-1970s, the coldest period in the entire 20th Century for the region. The Southeast and Northeast have underwent inconsequential warming compared to the West.

I will present examples of these errors from articles in diverse publications, including The Washington Post, National Geographic, and The Long Trail News.

Session 9, Topics in Applied Climatology III
Wednesday, 20 January 2010, 1:30 PM-2:30 PM, B211

Previous paper  

Browse or search entire meeting

AMS Home Page