The document summarizes recent changes observed in the Arctic climate that exceed expectations from climate models. These changes include a record low September sea ice extent in 2007 that was 23% below the previous record, younger and thinner Arctic sea ice, and rising permafrost temperatures across the Arctic. While natural variability and factors like the North Atlantic Oscillation contributed to changes in the past, many scientists are now convinced that greenhouse gas emissions are playing a role in driving changes in the Arctic that are faster than predicted by earlier climate models.