20th century data has shown a warming trend of as much as 5° C over extensive land areas in the region; since the 1950s there has been a significant decrease in summer sea ice extent; and new areas of extensive permafrost thawing have developed.

The polar environment is highly sensitive to changes in temperature and precipitation patterns with significant implications for Arctic plants, animals, and inhabitants. Impacts can occur on many scales: from Arctic ice algae and other micro-organisms, to walrus and polar bear populations and to Arctic human inhabitants, such as the Inuit.

Sea ice is critical to energy exchange between ocean and atmosphere limiting the exchange of carbon dioxide between water and air as well as the penetration of light into the water. Thus, changes in sea ice would affect the productivity of algae and plankton impacting vital marine systems. Thawing permafrost could have adverse effects on terrestrial environments. Changes in migration routes, food chains, wildlife interactions, and changes in species composition could result. Arctic peoples directly dependent on climate for access to game animals, fishing and hunting grounds, and suitable places for settlement would also be affected.

• The ice thickness of Alaskan glaciers has decreased by around 30 feet over the last forty years.
• Large areas of open water, called "leads", have opened in the Arctic sea ice with increasing regularity.
• Current atmospheric models project a pronounced warming over the Arctic as melting snow and ice lead to accelerated absorption of sunlight.
• While the Arctic warming of the recent decades may have multiple causes, long-term temperature records from tree rings, ice cores, lake bed pollen samples, and sediment analysis indicate that the Arctic is warmer now than any time during
  the previous 10,000 years.