Warming World Has No Greenland Ice, Less California Rain
LONDON, UK, April 8, 2004 (ENS) - Global warming that continues for several hundred years could cause the Greenland ice sheet to disappear, with a related seven meter (23 foot) rise in sea level that would inundate sea coasts around the world, warns a new study by an international team of scientists.
The paper concludes that the "removal of the Greenland ice sheet due to prolonged climatic warming would not be reversible."
Originally published in the "Journal of Climate" earlier this year, and republished today in the in the British science journal "Nature," the study is based on an advanced computer model of future climate trends.
They are joined for this study by glaciologist Dr. Philippe Huybrechts of the Alfred Wegener Institute, Germany's leading institute for polar and marine research.
The scientists used the HadCM3 - a coupled atmosphere-ocean general circulation model developed at the Hadley Centre - to simulate the global and regional climate with preindustrial atmospheric greenhouse gas composition and also with the Greenland ice sheet removed.
They forecast how the world's second largest ice sheet, after Antarctica, behaves as various levels of carbon dioxide (CO2) are emitted by the combustion of fossil fuels - oil, coal and natural gas.
The authors report that the lowest CO2 concentration used in the model, of 450 parts per million (ppm), is almost certain to be exceeded by 2050.
"This would mean a global average sea-level rise of seven metres during the next 1,000 years or more," they conclude.
Even if carbon dioxide concentrations in the atmosphere returned to pre-industrial levels, the ice sheet would not regenerate, the study finds, because the bare land will have lost its white covering and thus its ability to cool the planet by reflecting sunlight away from the surface.
A separate climate study published today in the "New Scientist" warns that by 2050, cities and towns along the west coast of the United States could be experiencing a serious water shortage, due to global warming.
Using a different climate model, Jacob Sewall and Lisa Cirbus Sloan from the University of California at Santa Cruz found that as Arctic sea ice melts, annual rainfall may drop by as much as 30 percent from Seattle to Los Angeles, and inland as far as the Rocky Mountains.
As temperatures rise over the next 50 years, the area of Arctic sea ice is predicted to shrink by as much as 50 percent in some areas during the summer.
They found that the effects on Europe were not severe, but the model showed that the sea ice changes are likely to mean significantly fewer storms will pass over the west coast of the United States.
"Winter sea ice acts like an insulating lid," explains Sewall. "When the lid is reduced, more heat can escape from the ocean to warm the atmosphere."
Towers of warm air form above areas where sea ice has been lost, and that disturbs the flow of air in the atmosphere around them, "like the supports under a bridge alter the flow of water in a river," they write.
Such towers formed between Norway and Greenland, deflecting winter storms that would otherwise have passed over the west coast of the United States towards northern British Columbia and southern Alaska. These areas received six percent more rain, while southern British Columbia down to southern California suffered a 30 percent drop in precipitation.
The researchers will publish their results in a future issue of "Geophysical Research Letters."
The United Nations' Kyoto Protocol is the only international agreement in place which requires industrial countries to limit greenhouse gas emissions by an average of 5.2 percent during the first commitment period 2008 to 2012.
While the protocol has been ratified by the European Union, Canada and Japan, which are already taking steps to limit their emissions, it will not become legally binding until Russia ratifies, and Russia has still not committed to ratification of the agreement.
Early in his term, President George W. Bush pulled the United States, the world's biggest emitter of greenhouse gases, out of the protocol process, saying the economic consequences were not worth the climate gains.