经济学人259:平流层的变化能引发讨人厌的寒流

 　　Climate and the solar cycle

　　气候和太阳圈
　　Chilling out in the winter sun
　　在冬日的阳光中发冷
　　Stratospheric changes can lead to nasty cold snaps
　　平流层的变化能引发讨人厌的寒流
　　THOSE unconvinced—and those seeking to unconvince others—of the reality of man-made global warming often point to the changeable behaviour of the sun as an alternative hypothesis. A new study showing how the severity of winters in Europe, and warming in the Arctic, might be linked to changes in solar activity might seem to add to this case. In itself, it does not, for the heat (or, rather, the cold) in question is being redistributed, not retained. But it does point to two other lessons about climate change: that hard data on the factors which affect it are sometimes difficult to come by; and that computer models of the climate can be quite impressive tools for working out what is going on.
　　不相信全球变暖是人为因素造成的和那些企图让别人不相信的人常常会将太阳的易变表现作为假设进行选择。一项新的研究正在致力于研究欧洲的严冬和日渐变暖的北极圈与太阳的变化活动可能的关联，似乎是为了证明此观点。实则不然，因为受人质疑的太阳热能（或者说冷能）一直在重新分布，而不是保持不变的。但这项研究却让人们从气候变化中学到了其他两点：影响因子的数据有时候很难得到；气候的电脑模型能够模拟出现在的气候状况，让人印象深刻。
　　The sun’s activity waxes and wanes 1 on an 11-year cycle, and over this cycle the amount of ultraviolet (UV) light the sun emits changes a lot more than does the total amount of energy. The stratosphere, the part of the Earth’s atmosphere which does most to absorb UV, might thus be expected to be particularly sensitive to the cycle.
　　太阳的活动周期是11年，在此周期内太阳散发出的紫外线总量的变化比太阳能总量的变化要大的多。吸收大部分紫外线的平流层?——地球大气圈的一部分，在此周期内可能会变得异常敏感。
　　In a paper just published in Nature Geoscience, Sarah Ineson of Britain’s Meteorological Office and her colleagues compared the way that the Met Office’s new and putatively 2 improved climate model dealt with winters at times of high UV and at times of low UV, using data on the amount of ultraviolet the sun gives off that were collected by a satellite called SORCE.
　　刚刚在《自然-地球科学》杂志上发表的一篇论文中，英国气象办公室的沙哈.伊内森和她的同事用该气象办公室公认的新型气候改进模型，对其在冬天纪录的高紫外线和低紫外线数据进行比较，这些数据是由一架名叫SORCE的卫星收集太阳散发的紫外线量获得的。
　　Dr Ineson found that at low UV levels the stratosphere in the tropics was cooler, because there was less UV for it to absorb, which meant the difference in temperature between the tropical stratosphere and the polar stratosphere shrank. That changed the way the atmosphere circulated, and as those changes spread down into the lower atmosphere they made it easier for cold surface air from the Arctic to come south in winter, freezing chunks 3 of northern Europe. These conditions looked similar to those seen in the past two cold European winters—which occurred at a time of low solar activity. The Arctic itself, in models and in real life, was warmer than usual, as were parts of Canada. In contrast, northern Europe, swathes of Russia and bits of America were colder.
　　伊内森博士发现热带地区平流层中的紫外线含量低，因而就更凉爽，因为那里没有足够的紫外线可以吸收，也就意味着热带地区平流层的气温和极地地区平流层的气温差异很大。这种情况改变了大气环流的方式。冬天，当大气环流变化散布到低一点的大气中时，自北极圈表层而来的冷空气很容易就能传播到南方，让北欧的大部分国家处于冰冻之中。这些状况和过去的两次发生在欧洲的严冬很相似——那两次严冬都发生在太阳活动频率很低的时候。而北极圈本身，无论是作为模型还是实际情况，都比平常要温暖，加拿大部分地区也是如此。临近俄罗斯和美国的北欧则相反，显得比平时更冰冷。
　　Why had this solar effect not been seen before? To some extent it had. Earlier modelling of a period of prolonged low solar activity in the 17th and 18th centuries showed similar patterns. That models of today’s climate had not was, in part, because they used much lower estimates of the amount of UV variation over the solar cycle than those derived 4 from the SORCE data, the most precise to be taken from a satellite looking at the sun. It may just be that working with more realistic data made the model work better.
　　为什么我们之前没有看出这种日光影响呢？某种程度上，我们看到过。更早以前，对17、18世纪时太阳活动持续不活跃的那段时期所做的模型也体现了同样的结构。但如今的气候模型却没有体现出来。部分原因是因为对太阳圈内紫外线变化量的估计比直接从SORCE中得来的要低的多。SORCE观察太阳所得出的数据，比其他的卫星更为精准。那么用更为接近实际的数据做模型或许更为可靠。
　　This does not mean the question is settled. Some scientists suspect the SORCE data may be exaggerating the sun’s variability, and if they were revised the link might go away. There are other theories around seeking to explain the recent cold winters, too. Improving predictions of future cold winters on the basis of this work, as the researchers say they would like to do, may thus prove hard.
　　这并不意味着问题解决了。一些科学家怀疑SORCE的数据可能夸大了太阳的变化性，如果数据一经修改，两者的关联可能也不复存在了。还有其他一些理论也正寻求解释最近冷冬的原因。研究员们说，他们想通过这些理论模型来改进预测未来冷冬的准确性，但看来并不那么容易。
　　But though global warming has made people look to models as predictors of the future, that is not their strongest suit. Something they can do much better is look at what happens when a variable such as UV is altered, compare that with the data, and thus gain insight into the mechanisms 6 by which climate works. This new research provides a good example of what such an approach can achieve.
　　尽管全球变暖让人们将模型视为未来的预言者，这却不是模型的最大作用。它们还有更大的作用，它们能观察当一个变量改变时（如紫外线）会发生什么，并与数据作比较，从而洞察出气候变化的机制。这项新的研究为这种方法所能取得的结果提供了好的例子。
　　stratospheric adj. 同温层的, 平流层的 alternative adj. 非此即彼的; 供选择的 stratosphere n.同温层 putatively adv. 推定地 circulate v. 循环 exaggerate v. 夸张, 夸大 mechanism 5 n. 机械