Date:7/29/2010

ne in 2002. The reconstructed summer temperatures of the last four centuries from Lapland and the Kola and Taimyr Peninsulas are similar in that all three data series display a temperature peak in the middle of the twentieth century, followed by a cooling of one or two degrees. Only the data series from the Yamal Peninsula differed, reaching its peak later, around 1990. What stands out in the data from the Kola Peninsula is that the highest temperatures were found in the period around 1935 and 1955, and that by 1990 the curve had fallen to the 1870 level, which corresponds to the start of the Industrial Age. Since 1990, however, temperatures have increased again evidently. What is conspicuous about the new data is that the reconstructed minimum temperatures coincide exactly with times of low solar activity. The researchers therefore assume that in the past, solar activity was a significant factor contributing to summer temperature fluctuations in the Arctic. However, this correlation is only visible until 1970, after which time other possibly regional factors gain the upper hand. "One thing is certain: this part of the Arctic warmed up after the end of the Little Ice Age around 250 years ago, cooled down from the middle of the last century and has been warming up again since 1990," says Dr Tatjana Bttger, a paleoclimatologist at the UFZ.

In September 2009, another international team presented model calculations showing that the Arctic had gradually cooled down by around 0.2 C per thousand years over the last two millennia to the start of the Industrial Age. They attributed this to a gradual decline in solar radiation in the summer. However, the last decade was the warmest of the Common Era and was 1.4 C above the forecasts, report Darrell S. Kaufman and his colleagues in Science. The new data produced by Kononov, Friedrich and Bttger support the thesis that solar activity seems to be a significant factor influencing summer temperatures in the Arctic, but that
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Contact: Tilo Arnhold presse@ufz.de 49-341-235-1635 Helmholtz Association of German Research Centres Source:Eurekalert

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