MOSCOW, November 24 — RIA Novosti. Analysis of Arctic climate over the last 1.5 thousand years shows that the current reduction in sea ice, unprecedented in scale, due to human activities, according to the authors of an article published in the journal Nature.
Lonnie Thompson (Lonnie Thompson) from the Center named after Byrd Polar Research (USA) and his colleagues first used a model for the Arctic, which is widely used by climate scientists to reconstruct the surface temperature of the Earth for a period of several thousand years.
According to the National Information Center for Snow and Ice (NSIDC) USA, for the period of regular observations, which are conducted in 1979, the summer ice cover has shrunk by about a third. The absolute minimum was reached in September 2007 — about 4 million square kilometers, nearly 3 million square kilometers less than the average for the period from 1979 to 2000.
According to the authors, until now it was impossible to give a reasonable answer to the question whether these anomalous fluctuations in ice area, since all calculations were based on too short a period of significant observations — 40-50 years.
Based on the fact that the same climatic processes influence the area of ice in the Arctic and on the nature of the Arctic coast, Thompson and his colleagues selected 69 key indicators for which information is available. A comparison of these parameters within a single model has made it possible to calculate the algorithms of their relationship, and "rewind" climate history back to simulate the changes in the area of ice cover.
Among the authors of the selected set of 52 indicators point data of the limits of distribution of ice, 11 retrospective series of temperatures, reduced the thickness of tree rings, four studies of sediments in Arctic lakes, as well as two series of continuous observations of the characteristics of the ice.
"While there is considerable uncertainty, especially in the period up to the 16th century, as the duration and extent of the current trend of decreasing ice cover seems to have no parallel in the last 1450 years … These results support the fact that the ice cover — active component of climate variability in the Arctic, and its decline in recent years due to anthropogenic warming, "- says the article.