Science and technology.Climate change.Good news at last?The climate may not be as sensitive to carbon dioxide as previously believed.CLIMATE science is famously complicated, but one useful number to keep in mind is "climate sensitivity".This measures the amount of warming that can eventually be expected to follow a doubling in the atmospheric concentration of carbon dioxide.The Intergovernmental Panel on Climate Change, in its most recent summary of the science behind its predictions, published in 2007, estimated that, in present conditions, a doubling of CO2 would cause warming of about 3°C, with uncertainty of about a degree and a half in either direction.But it also says there is a small probability that the true number is much higher.Some recent studies have suggested that it could be as high as 10°C.If that were true, disaster beckons.But a paper published in this week's Science, by Andreas Schmittner of Oregon State University, suggests it is not.In Dr Schmittner's analysis, the climate is less sensitive to carbon dioxide than was feared.Existing studies of climate sensitivity mostly rely on data gathered from weather stations, which go back to roughly 1850.Dr Schmittner takes a different approach.His data come from the peak of the most recent ice age, between 19,000 and 23,000 years ago.His group is not the first to use such data (ice cores, fossils, marine sediments and the like) to probe the climate's sensitivity to carbon dioxide.
科技。气候变化。终于来了好消息？气候对二氧化碳的敏感性可能低于先前的预期。气候科学的复杂程度众所周知，但把一个指标记在脑中非常好用，那就是"气候敏感性"。该指标表示预计大气中二氧化碳浓度翻倍所能引致的升温量。政府间气候变化专门委员会（IPCC）在其最近一次关于其预测背后的科学性的概要中（发布于2007年）估计，在如今的情况下，二氧化碳浓度翻倍将造成3°C左右的升温，上下误差在1.5度左右。但该概要也声称，真实数据有少许可能还要高得多。一些近期的研究也猜测气温上升可能达到10°C之高。如果这种猜测属实，灾难说来就来了。但美国俄勒冈州立大学的安德烈亚斯-施密特纳在本周《科学》杂志上刊登的一篇报告认为，情况并非如此。在施密特纳博士的分析中，气候并不像先前人们所担忧的那样对二氧化碳那么敏感。现有的关于气候敏感性的研究主要基于气象站收集的数据，可以追溯到公元1850年左右。施密特纳博士采用了另外一种方法。他的数据来源于最近一次冰河时期的顶峰（介于一万九千到两万三千年前之间）。他的团队不是第一个使用这些数据（冰芯，化石，海洋沉积物诸如此类）来探测气候对二氧化碳的敏感性的团队。
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