Scientists Link Thaw to Global Warming, Not Regional Weather
Greenland's massive ice sheet could begin to melt this century and may disappear completely within the next thousand years if global warming continues at its present rate.
Greenland has melted more in recent summers than at any time in at least 50 years, a finding that supports the link between global warming, the melting of the Arctic and Greenland and sea level rise.
According to a new climate change study, the melting of Greenland's ice sheet would raise the oceans by seven meters (23 feet), threatening to submerge cities located at sea level, from London to Los Angeles.
The international research team was led by Edward Hanna of the University of Sheffield, and the study published the results of their climate and glacier data analysis in the Journal of Climate Jan 15.
Whereas melting in the 1960s through the early 1990s corresponded with regional variations in temperature, the melting since then has corresponded with global changes in temperatures, the scientists wrote.
Three recent summers – 2003, 2005 and 2007 – have topped the list of seasons that caused the most melting. Arctic sea ice also hit new record-lows during those years, though the records were set in different years – 2003 for Greenland and 2007 for the Arctic.
Scientists have previously calculated that if the annual average temperature in Greenland increases by almost 3° Celsius (5.4° Fahrenheit), its ice sheet will begin to melt.
Many experts believe the concentration of carbon dioxide in the atmosphere will have reached levels around the year 2100 that would cause the temperature to rise that much.
"We're not saying how long it will take to get to the three degrees or how long it will take to lose the ice sheet," Gregory said. "We're saying there's a high likelihood of passing this threshold of viability with the carbon dioxide levels that are currently being considered."
Some of the world's top experts and institutions worked on this study: the Free University of Brussels, the University of Colorado, the Danish Meteorological Institute and the NASA Goddard Earth Science and Technology Center, the University of Maryland Baltimore County.
"Our work shows that global warming is beginning to take its toll on the Greenland Ice Sheet which, as a relict feature of the last Ice Age, has already been living on borrowed time and seems now to be in inexorable decline," Hanna said. "The question is can we reduce greenhouse-gas emissions in time to make enough of a difference to curb this decay?"
At stake is the level of sea levels around the world, and the rapidity with which they will increase. The melting of the Greenland ice sheet is a key factor in sea levels. It could take centuries, but the melting of Greenland could increase sea levels more than 20 feet – enough to swamp coastal cities like Los Angeles, New York and New Orleans.
Also, replacing snow and ice in Greenland and the Arctic would allow water and land to absorb more sunlight, leading to increasingly warm temperatures that could have a major influence on world weather patterns. Turn off the air conditioner, and a hot day seems hotter.
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