北极冰川融化速度比预期快

As government officials from eight Arctic nations - the United States, Russia, Canada, Sweden, Finland, Denmark, Norway and Iceland -  prepare to meet in Greenland next week to discuss the challenges of climate change, a report released May 4, 2011 underscores the urgency of the Arctic Council meeting.  The study finds the Arctic's polar ice is melting at a much faster rate than previously thought.

The report was released by the Arctic Monitoring and Assessment Program, the scientific arm of the 8-nation Arctic Council. It finds that the past six years - between 2005 and 2010 - were the warmest years recorded in the Arctic since measurements began in 1880.

Gordon Hamilton is a leading glaciologist and professor at the University of Maine Climate Change Institute. He says the new assessment updates the U.N.’s Climate Change Panel’s 2007 report with data on Arctic conditions over the past five years. 

"And so with our new understanding on how ice sheets are behaving and how they are responding to climate change we can say that the IPCC [UN Intergovernmental Panel on Climate Change] estimate for sea level rise from 18 to 59 centimeters is a very large underestimate and we are looking at something probably double the upper end of the estimate. So we are expecting one meter of sea level rise by 2100," said Gordon Hamilton.

Melting from Arctic glaciers, ocean ice and the Greenland ice sheet will make substantial contributions to that sea level rise, the report finds.  Hamilton says while the year 2100 may seem like a long way off, the new estimates can help policy makers address changes in coastal areas where more than half the world’s population lives.    

"If you’re building coastal structures or if you are planning development in coastal zones, these are the types of human activity that take place over the course of decades and so we need to be making these decisions with the best sea level estimates in hand," he said.

Hamilton is amazed at the rate of change he’s witnessed in polar regions.

"In my field, glaciology, six years ago we didn’t think that ice sheets responded to climate change on a time scale any shorter than a few thousand years, whereas now we are seeing the big ice sheets in Greenland and west Antarctica respond in just a few months to triggers that are coming from the climate systems," said Hamilton.

The extent and duration of snow cover have decreased throughout the Arctic, falling by 18 percent since 1966. Other accelerated changes, Hamilton says, include the rapid decline of sea ice.

"A few years ago the projection was that the Arctic Ocean would be ice-free in the summers by the year 2080," he said. "Well, in the first few years of this decade there were some extraordinarily fast declines in Arctic sea ice."

The report finds that the Arctic Ocean could become nearly ice-free in the summers within the next thirty to forty years. Hamilton says there is still time to act to slow down these changes by drastically reducing climate-changing carbon emissions, initiatives that he hopes the Arctic country ministers adopt when they meet next week in Greenland.