Study: Cool Spells Normal in Warming World, By ANDREW C. REVKIN, April 3, 2009, 2:15 PM, www.dotearth.blogs.nytimes.com
A valuable short paper that has been accepted for publication in Geophysical Research Letters (subscription required) shows [that global warming will not proceed in a straight-line fashion, with each successive year warmer than the last], . . . that we can get a 10- or even 15-year period with no real change in globally averaged temperature even though in the end we have strong global warming.
. . . Recent records and projections using computer simulations show how normal it is to have decade-long variation in temperature, up and down, on the way to a warmer world. The paper is titled simply, “Is the climate warming or cooling?” It is written by David R. Easterling of the National Climatic Data Center and Michael F. Wehner of the Lawrence Berkeley National Laboratory.
The bottom line? “We show that the climate over the 21st century can and likely will produce periods of a decade or two where the globally averaged surface air temperature shows no trend or even slight cooling in the presence of longer-term warming,” the paper says, adding that, “It is easy to ‘cherry pick’ a period to reinforce a point of view.”
I asked Dr. Easterling why they pursued this effort, which somewhat replicates findings of the Intergovernmental Panel on Climate Change, but perhaps with a more pointed goal. Here’s his reply:
To show, in a peer-reviewed scientifically defensible way that there is no reason to expect the climate to warm in a monotonic type fashion, that there is natural variability along with anthropogenic forced warming and we shouldn’t expect each year to be warmer than the next or even a run of 10 years always to show warming. That we can get a 10- or even 15-year period with no real change in globally averaged temperature even though in the end we have strong global warming.