OPINION/COMMENTARY

New Swedish Study Shows ‘Natural Variability’ in Climate

A new paleoclimatological study, “Highly variable Northern Hemisphere temperatures reconstructed from low and high resolution data,” published as a letter in the February 10 issue of Nature, finds that there has been significant natural variability in the climate over the past 2,000 years. The authors are Anders Moberg, Karin Holmgren, and Wibjorn Karlen of Stockholm University and Dmitry M. Sonechkin and Nina M. Datsenko of the Hydrometeorological Research Center of Russia. The most important point of the study, according to the Swedish Research Council, is that it “shows that natural climate change may be larger than generally thought. “The most widespread picture of climate variability in the last millennium [the ‘hockey stick’] suggests that only small changes occurred before the year 1900, and then a pronounced warming set in. The new results rather show an appreciable temperature swing between the 12th and 20th centuries, with a notable cold period around AD 1600. A large part of the 20th century had approximately the same temperature as the 11th and 12th centuries. Only the last 15 years appear to be warmer than any previous period of similar length....

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