tailieunhanh - COSEE-West Lecture

Check out these fast facts for a snapshot of Earth's evolving climate. ∗ There is little doubt that the planet is warming. Over the last century the average temperature has climbed about 1 degree Fahrenheit ( of a degree Celsius) around the world. The spring ice thaw in the Northern Hemisphere occurs 9 days earlier than it did 150 years ago, and the fall freeze now typically starts 10 days later. ∗ The multinational Arctic Climate Impact Assessment (ACIA) report recently concluded that in Alaska, western Canada, and eastern Russia, average temperatures have increased as much as 4 to 7. | C 5tt West COSEE-West Lecture November 16 2005 Glaciers and Global Sea Level Rise Fast Facts Check out these fast facts for a snapshot of Earth s evolving climate. There is little doubt that the planet is warming. Over the last century the average temperature has climbed about 1 degree Fahrenheit of a degree Celsius around the world. The spring ice thaw in the Northern Hemisphere occurs 9 days earlier than it did 150 years ago and the fall freeze now typically starts 10 days later. The multinational Arctic Climate Impact Assessment ACIA report recently concluded that in Alaska western Canada and eastern Russia average temperatures have increased as much as 4 to 7 degrees Fahrenheit 3 to 4 degrees Celsius in the past 50 years. The rise is nearly twice the global average. In Barrow Alaska the . s northernmost city average temperatures are up over 4 degrees Fahrenheit to 3 degrees Celsius in 30 years. The United Nations Intergovernmental Panel on Climate Change IPCC projects that global temperatures will rise an additional 3 to10 degrees Fahrenheit to degrees Celsius by century s end. Over the last million years the Earth has fluctuated between colder and warmer periods. The shifts have occurred in roughly 100 000-year intervals thought to be regulated by sunlight. Earth s sunlight quota depends upon its orbit and celestial orientation. Rising temperatures have a dramatic impact on Arctic ice which serves as a kind of air conditioner at the top of the world. Since 1978 Arctic sea ice area has shrunk by some 9 percent per decade and thinned as well. ACIA projects that at least half of the Arctic s summer sea ice will melt by century s end and that the Arctic region is likely to warm 7 to 13 degrees Fahrenheit 4 to 7 degrees Celsius during the same time. Over the very long term Greenland s massive ice sheet holds enough melt water to raise sea level by about 23 feet about 7 meters . ACIA climate models project significant melting of the sheet .