Read Online With Speed and Violence: Why Scientists Fear Tipping Points in Climate Change by Fred Pearce - Free Book Online Page B
Authors: Fred Pearce
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equilibrium line remaining roughly stationary. Glaciologists have regarded this balance as rather secure, since such huge volumes of ice can change only very slowly. Glacially. This image of stability and longevity is reassuring. If the ice sheets all melted, or slumped into the ocean, they would make a big splash. They contain enough ice to raise sea levels worldwide by 230 feet. That would drown my house, and probably yours, too. Luckily, as glaciologists have been telling us for years, this won't happen. Not even if there is fast global warming. Large ice sheets, they say, tend to maintain their own climate, keeping the air above cold enough to prevent large-scale melting. And even if warming did take hold at the surface, it could penetrate the tightly packed ice only extremely slowly.
The scariest suggestion, made by the IPCC in 2001, was that beyond a warming of about 5°F, Greenland might gradually start to melt, with a wave of warmth moving down through the ice. Once under way, the process might be unstoppable, because as the ice sheet melted, its surface would lower and become exposed to ever-warmer air. But the melting would take place very slowly, "during the next thousand years or more." Now, that is not a nice legacy to leave to future generations, but a thousand years is forty or so generations away. So maybe it is not something to worry us today.
That used to be the scientific consensus. But Hansen is the spokesperson for a growing body of glaciologists who say that things could happen much faster. Because ice sheets, even the biggest and slowest and most stable-looking, have a secret life involving dramatic and dynamic change. And their apparent stability could one day be their undoing. The story is told best in a single picture. Hansen's "slippery slope" caption accompanied a photograph of a river of water flowing across the Greenland ice sheet and pouring down a hole. The photo has an apocalyptic feel, and in the top right-hand corner a couple of researchers look on from a distance, giving an awesome sense of scale.
What is going on here? The water is not entirely new. Small lakes have always formed on the surface of Greenland ice in the summer sun. And sometimes those lakes empty down flaws in the ice-whether crevasses or vertical shafts, which are known to glaciologists as moulins. But what is new is the discovery that as the surface warms, more and more water is pouring into the interior of the ice sheet. Waterfalls as high as 2 miles are taking surface water to the very base of the ice, where it meets the bedrock. "The summer of 2005 broke all records for melting in Greenland," says Hansen. And such melting threatens to destabilize large parts of the ice sheet on timescales measured in years or decades, not millennia.
Jason Box, of Ohio State University, is a young researcher who knows more about this than most. Every year, he visits Swiss Camp, a research station set up in r 990 on Greenland ice. The name was chosen by the camp's founder, Konrad Steffen, of Zurich, so that he felt more at home. The station was originally sited on the equilibrium line, where the ice melt in summer exactly matches the accumulation of new snow in winter. But the equilibrium line has since moved many miles north, as ever-larger chunks of Greenland find themselves in the zone of predominant melting. These days, Box goes boating in an area close to Swiss Camp dubbed the "Greenland Lake District." "Some of these lakes are three or four miles across and have lasted for a decade or more now," he says. "You wouldn't think it was Greenland at all."
The lakes are more than just symptoms of melting. They are also reservoirs for the destruction of the ice sheet. "These lakes keep growing and growing until they find a crevasse, into which they drain,"Box says. "Down there are extensive river systems, between the ice and the hard rock, that eventually emerge at the glacier snout. There may be great lakes, too."
Another regular
The scariest suggestion, made by the IPCC in 2001, was that beyond a warming of about 5°F, Greenland might gradually start to melt, with a wave of warmth moving down through the ice. Once under way, the process might be unstoppable, because as the ice sheet melted, its surface would lower and become exposed to ever-warmer air. But the melting would take place very slowly, "during the next thousand years or more." Now, that is not a nice legacy to leave to future generations, but a thousand years is forty or so generations away. So maybe it is not something to worry us today.
That used to be the scientific consensus. But Hansen is the spokesperson for a growing body of glaciologists who say that things could happen much faster. Because ice sheets, even the biggest and slowest and most stable-looking, have a secret life involving dramatic and dynamic change. And their apparent stability could one day be their undoing. The story is told best in a single picture. Hansen's "slippery slope" caption accompanied a photograph of a river of water flowing across the Greenland ice sheet and pouring down a hole. The photo has an apocalyptic feel, and in the top right-hand corner a couple of researchers look on from a distance, giving an awesome sense of scale.
What is going on here? The water is not entirely new. Small lakes have always formed on the surface of Greenland ice in the summer sun. And sometimes those lakes empty down flaws in the ice-whether crevasses or vertical shafts, which are known to glaciologists as moulins. But what is new is the discovery that as the surface warms, more and more water is pouring into the interior of the ice sheet. Waterfalls as high as 2 miles are taking surface water to the very base of the ice, where it meets the bedrock. "The summer of 2005 broke all records for melting in Greenland," says Hansen. And such melting threatens to destabilize large parts of the ice sheet on timescales measured in years or decades, not millennia.
Jason Box, of Ohio State University, is a young researcher who knows more about this than most. Every year, he visits Swiss Camp, a research station set up in r 990 on Greenland ice. The name was chosen by the camp's founder, Konrad Steffen, of Zurich, so that he felt more at home. The station was originally sited on the equilibrium line, where the ice melt in summer exactly matches the accumulation of new snow in winter. But the equilibrium line has since moved many miles north, as ever-larger chunks of Greenland find themselves in the zone of predominant melting. These days, Box goes boating in an area close to Swiss Camp dubbed the "Greenland Lake District." "Some of these lakes are three or four miles across and have lasted for a decade or more now," he says. "You wouldn't think it was Greenland at all."
The lakes are more than just symptoms of melting. They are also reservoirs for the destruction of the ice sheet. "These lakes keep growing and growing until they find a crevasse, into which they drain,"Box says. "Down there are extensive river systems, between the ice and the hard rock, that eventually emerge at the glacier snout. There may be great lakes, too."
Another regular
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