The first thorough assessment of the impact climate change is having on the Arctic concludes that the region is warming rapidly and that environmental effects are already starkly visible.

"Over the past 30 years, the average annual temperature in the Arctic has risen more rapidly than anywhere on Earth," Robert W. Corell, who chaired the study, told a symposium in Washington, D.C., last month. In some regions, "temperatures rose five to 10 times the global average," he explained. Corell is a senior fellow at the American Meteorological Society.

The report, commissioned by eight nations with Arctic territory, including the U.S., was prepared over four years by about 300 scientists and representatives of Arctic indigenous people. The full report will be officially released on Nov. 9 at a conference in Reykjavík, Iceland, where researchers will discuss the findings.

During the 21st century, the study says, warming in the Arctic is expected to be even more severe unless greenhouse gas emissions are cut dramatically. The extent of Arctic summer sea ice, which has already declined 15 to 20%, could dwindle to zero by 2040, according to one model.

The retreat of sea ice, the study notes, is already harming polar bears and seals, which depend on sea ice near land in the breeding season. The changes are also depleting the food supply of the indigenous people who rely on these animals.

The warming trend in the Arctic will have global impacts, the report notes. The most damaging effect will be sea-level rise, as melting of the 2-mile-thick Greenland Ice Sheet accelerates. "Recent research suggests a sea-level rise of up to 1 to 2 meters during this century," unless large cuts are made in CO₂ emissions, Corell said.