The strongest effect is in the Arctic, where temperatures have warmed by over 3.5 degrees Fahrenheit in the last 40 years. Summer minimum sea ice coverage in the Arctic was the second-lowest on record in 2008, behind 2007, which broke the previous record low by more than 20 percent. The sea ice losses in the Arctic contribute to warmer land temperatures in the area, which in turn can lead to increased permafrost melting and the release of additional greenhouse gases, Monaghan said. The Antarctic shows a smaller but still significant overall warming trend. While some parts of the continent appear to be cooling, such as over the South Pole, warming is pronounced over West Antarctica and the Antarctic Peninsula. Warming in these coastal regions may lead to collapse into the ocean of ice sheets -- including the 2002 loss of the larger-than-Rhode-Island Larsen B ice sheet -- which contribute to sea level rise. Measuring trends in the Antarctic is more difficult because there are fewer than 20 data stations, and they have been operating for fewer years than in the Arctic. "In my mind, the most important issue is the potential implication of polar ice sheet melt on sea level rise," Monaghan said, "At the same time we have this increased sense of urgency to gain a better understanding of the various factors that influence polar climate variability and especially whether humans are playing a role. So that's why this study is so important. It formally demonstrates the human contribution for the first time." Related Links: National Snow and Ice Data Center Slide Show: Arctic Sea Ice Approaches Record Low Treehugger: Arctic Just Witnessed Fastest August Ice Retreat in History |
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