J. Nevertheless, there is some cause for nervousness. As the ACIA researchers document, there are signs that the massive Greenland ice sheet might be melting more rapidly than was thought a few years ago. Cracks in the sheet appear to be allowing melt water to trickle to its base, explains Michael Oppenheimer, a climatologist at Princeton University who was not one of the reports authors. That water may act as a lubricant, speeding up the sheets movement into the sea. If the entire sheet melted, the sea might rise by 6-7 meters. But when will this kind of disastrous ice disintegration really happen? While acknowledging it this century is still an unlikely outcome, Dr. Oppenheimer argues that the evidence of the past few years suggests it is more likely to happen over the next few centuries if the world does not reduce emissions of greenhouse gases. He worries that an accelerating Arctic warming trend may yet push the ice melt beyond an irreversible on / off switch.
K. That is scary stuff, but some scientists remain unimpressed. Patrick Michaels, a climatologist at the University of Virginia, complains about the ACIAs data selection, which he believes may have produced evidence of spurious warming. He also points out, in a new book, that even if Arctic temperatures are rising, that need not lead directly to the ice melting. As he puts it, Under global warming, Greenlands ice indeed might grow, especially if the warming occurs mostly in winter. After all, warming the air ten degrees when the temperature is dozens of degrees below freezing is likely to increase snowfall, since warmer air is generally moister and precipitates more water.
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