Good news on global warming is thin on the ground(稀少，寥寥无几). But there may be some up in the air(悬而未决；在空中). Operation Blue Skies, announced on August 18th, is a scientific study being undertaken by Britain’s air-traffic-control service, NATS, and various organisations where people study the effects on climate of the streaks(条纹，条痕) of cloud created by aircraft—known as contrails(凝结尾迹（飞机尾迹）).
关于全球变暖的好消息少之又少。但空中或许有一些。8月18日宣布的“蓝天行动”是一项科学研究，由英国空中交通管制服务机构NATS以及多个研究飞机产生的云带（即尾迹）对气候影响的组织开展。
Over the next two winters the consortium aims to see if it is possible to reduce the number of persistent contrails—the class with the largest such effects—over a swathe of the North Atlantic, thereby measurably reducing the climate impact of civil aviation.(在接下来的两个冬天，该联盟旨在检验是否有可能减少北大西洋大片区域上空的持续性尾迹，从而显著降低民航的气候影响。) If this experiment works, a worldwide application of the same techniques might cut the climate effects of air travel by as much as(多达，和……一样多) half.
在接下来的两个冬天，该联盟旨在检验是否有可能减少北大西洋大片区域上空的持续性尾迹（这类尾迹的气候效应最大），从而显著降低民航的气候影响。如果这项实验奏效，全球应用同样的技术可能会将航空旅行的气候影响削减多达一半。
On a sunny day the wispy(纤细的，飘渺的) cirrus(卷云) clouds into which some contrails are transformed can look as if they might be cooling the planet in the manner of(以……的方式) a delicate parasol(阳伞). And some contrails do indeed cool things down beneath them a bit. But they also warm things up by trapping some of the upwelling(上涌的，上升的) infrared(红外线的) radiation that would otherwise(否则，要不然) escape into space. On average, that warming effect, found in all contrails (and the cirrus clouds they turn into), handsomely(相当大地，慷慨地) outweighs(超过，重于) the cooling provided by some. In the climate scheme of things, contrails are a liability(负担，累赘).
在晴朗的日子里，一些尾迹转化而成的缕缕卷云看起来就像精致的阳伞一样，可能正在给地球降温。有些尾迹确实会让其下方的东西稍微凉快一些。但它们也会通过捕获一些原本会逃逸到太空的上涌红外辐射而使东西变暖。平均而言，这种在所有尾迹（以及它们变成的卷云）中都能发现的增温效应，大大超过了某些尾迹提供的降温效应。从气候的角度来看，尾迹是一种负担。