New Swedish Study Shows ‘Natural Variability’ in Climate

New Swedish Study Shows ‘Natural Variability’ in Climate

Murray Op-ed in EU Reporter Online
March 13, 2005

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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 <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" />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...”The Research Council also points to another recent reconstruction that finds similar results and states:


“The fact that these two climate evolutions, which have been obtained completely independently of each other, are very similar supports the case that climate shows an appreciable natural variability—and that changes in the sun’s output and volcanic eruptions on the earth may be the cause.


“This means that it is difficult to distinguish the human influence on climate from natural variability, even though the past 15 warm years are best explained if one includes human influence in the simulations.


“The new study underscores the importance of including natural climate variability in future scenarios. It is not only the humans that can cause appreciable climate changes—nature does it all the time by itself.”