考研阅读精选：气候变化--终于传来了好消息
『研究发现，空气中的二氧化碳含量并不会对气候造成太大的影响，这一发现出乎我们的意料。』Climate change: Good news at last?
气候变化：终于传来了好消息
Nov 26, 2011 | from The Economist
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CLIMATE science is famously complicated, but one useful number to keepin mind is “climate sensitivity”. This measures the amount of warmingthat can eventually be expected to follow a doubling in the atmosphericconcentration of carbon dioxide. The Intergovernmental Panel on ClimateChange, in its most recent summary of the science behind itspredictions, published in 2007, estimated that, in present conditions, adoubling of CO2 would cause warming of about 3°C, with uncertainty ofabout a degree and a half in either direction. But it also says there isa small probability that the true number is much higher. Some recentstudies have suggested that it could be as high as 10°C.
If thatwere true, disaster beckons. But a paper published in this week’sScience, by Andreas Schmittner of Oregon State University, suggests itis not. In Dr Schmittner’s analysis, the climate is less sensitive tocarbon dioxide than was feared.
Existing studies of climatesensitivity mostly rely on data gathered from weather stations, which goback to roughly 1850. Dr Schmittner takes a different approach. Hisdata come from the peak of the most recent ice age, between 19,000 and23,000 years ago. His group is not the first to use such data (icecores, fossils, marine sediments and the like) to probe the climate’ssensitivity to carbon dioxide. But their paper is the most thorough.Previous attempts had considered only small regions of the globe. He hascompiled enough information to make a credible stab at recreating theclimate of the entire planet.
The result offers that rarest ofthings in climate science—a bit of good news. The group’s most likelyfigure for climate sensitivity is 2.3°C, which is more than half adegree lower than the consensus figure, with a 66% probability that itlies between 1.7° and 2.6°C. More importantly, these results suggest anupper limit for climate sensitivity of around 3.2°C.
Before youtake the SUV out for a celebratory spin, though, it is worth bearing inmind that this is only one study, and, like all such, it has its flaws.The computer model used is of only middling sophistication, DrSchmittner admits. That may be one reason for the narrow range of histeam’s results. And although the study’s geographical coverage is themost comprehensive so far for work of this type, there are still blankareas—notably in Australia, Central Asia, South America and the northernPacific Ocean. Moreover, some sceptics complain about the way ancientdata of this type were used to construct a different but related pieceof climate science: the so-called hockey-stick model, which suggeststhat temperatures have risen suddenly since the beginning of theindustrial revolution. It will be interesting to see if such scepticsare willing to be equally sceptical about ancient data when they supporttheir point of view. (476 words)
文章地址: http://www.economist.com/node/21540224
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