Background research of global warming

Earth's average temperature is becoming warmer. Because atmospheric warming will be most readily apparent in the melting of perennial and permanent ice, and because most glaciers are small relative to vast ice sheets and expansive sea ice, glaciers are important indicators of climate change.

• Over the past 100 years, global mean (average) sea level has been rising at an average rate of 1 to 2 millimeters per year. A possible contributor to sea-level rise is increased meltwater from the snow and ice of glaciers, ice sheets, ice caps, icebergs, and sea ice.



• Glaciers in Alaska and neighboring Canada, with a combined area of approximately 90,000 square kilometers (roughly 35,000 square miles), and accounting for about 13 percent of mountain glaciers on Earth, have thinned substantially. Over the last 40 years, thinning has been on the order of 50 to 100 meters (several hundred feet) at lower elevations of glacier occurrence, and about 18 meters (60 feet) at higher elevations.



• Many glaciers in South America's Andes are melting so fast that, if the current rate continues, they could disappear by 2020. The Quelccava glacier in Peru retreated 32 times faster during the period 1983–2000 than in the 20 years from 1963 to 1983. In the Patagonian ice fields of Argentina, glaciers have receded 1.5 kilometers since 1990.



• In Africa, Mount Kilamanjaro's ice fields have shrunk by a least 80 percent since 1912. Mount Kenya's ice cap has shrunk by 40 percent since the 1960s.



• The 15,000 glaciers of the Himalayas, which collectively constitute the largest body of ice outside the polar caps, are reported to be receding faster than anywhere on Earth. Some 2,000 have melted since the 1950s. Instead of snow accumulation in winter, Himalayan glaciers are being hit by summer monsoon rains. The Dokriani Barnak glacier has receded about 0.8 kilometer since 1990. If Himalayan glaciers recede at this rapid rate, they will be gone by 2035.

In the European Alps, several glaciers have disappeared entirely since the 1960s.

Permanent sea-ice cover in the Arctic Ocean is shrinking by an area the size of the Netherlands each year. The Arctic ice cap thinned from 3 meters (10 feet) in 1970 to 2 meters (nearly 7 feet) in 2000.

• In the Antarctic, rising temperatures have resulted in the collapse of massive ice shelves, some of which have been there for 20,000 years.*



• In Glacier National Park in Montana, the number of glaciers has dropped from an estimated 150 in 1850 to only 50 in 2000. At this rate of decline, all of the glaciers in the park will be gone by 2030.