U.S. Department of Energy Office of Biological and Environmental Research

BER Research Highlights

Is the Climate Warming or Cooling?
Published: April 27, 2009
Posted: May 18, 2009

The debate surrounding climate change and concerns for global warming are complicated by publications, websites, and blogs that often cite decade-long climate trends (e.g., from 1998-2008) in which the earth's average temperature dropped slightly as evidence that the global climate has stopped warming and begun to cool. In a forthcoming paper accepted for publication in Geophysical Review Letters, David R. Easterling of the National Climatic Data Center and Michael Wehner of the Lawrence Berkeley National Laboratory note that due to natural climate variability it is likely to have periods as long as a decade or two of cooling superimposed on the longer-term warming trend.  The authors studied the occurrence of decade-long trends in globally averaged surface air temperature using observed climate data from 1901-2008 and the CMIP3 archive of climate model simulations of the 20th century and found short periods of global cooling.  Similarly, computer simulations of 21st century climate showed that negative decadal trends are possible although the likelihood of such occurrences decreases into the future.  Easterling and Wehner conclude that selectively analyzing climate records to highlight short periods of either global cooling or exaggerated warming can be misleading in the context of the longer, sustained warming caused by human induced emissions of greenhouse gases.

Reference: Easterling, D. R., and M. F. Wehner. 2009. "Is the Climate Warming or Cooling?" Geophysical Review Letters 36, L08706. DOI: 10.1029/2009GL037810. (Reference link)

Contact: Anjuli Bamzai, SC-23.1, (301) 903-0294
Topic Areas:

  • Research Area: Earth and Environmental Systems Modeling

Division: SC-23.1 Climate and Environmental Sciences Division, BER


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