【经济学人】该如何拯救地球？ | 2016.11.12 | 总第728期

A feast in the air

大气的二氧化碳“盛宴 ”

IN 1972, on their way to the Moon, the crew of Apollo 17 snapped what would become one of the most famous photographs ever taken. The “Blue Marble” shows Earth as it looks from space: a blue sphere overlaid by large brown swatches of land, with wisps of white cloud floating above.

1972年，在飞往月球的路上，阿波罗17号的宇航员们拍下了一张照片（后来被命名为“蓝色大理石”），其后成为摄影界最著名的照片之一。 “蓝色大理石”展示了太空中的地球全景：一个蓝色球体，被大片棕色的土地覆盖，一缕缕白云在上空漂浮。

• wisps of white cloud:一缕缕白云

“蓝色大理石”

But times change, and modern pictures of Earth look different. A wash of greenery is spreading over the globe, from central Africa to Europe and South East Asia. One measurement found that between 1982 and 2009 about 18m square kilometres of new vegetation had sprouted on Earth’s surface, an area roughly twice the size of the United States.

但随着时代的变化，现代地球的图片看起来跟以前不一样了。从非洲中部到欧洲和东南亚地区，绿色植物遍布。在一次测量中人们发现，从1982年到2009年，地球的表面萌生了约1800万平方公里的新植被，面积约为美国的两倍。

• measurement:n.测量

• sprout:v.萌芽

The growth in greenery is a consequence of climate change. As the planet heats up, places that were once too chilly for most plants to grow have become steadily more hospitable . That extra vegetation, in turn, exerts its own effects on the climate. According to a team led by Trevor Keenan of the Lawrence Berkeley National Laboratory, in California, who have just published their findings in Nature Communications , the plant growth caused by climate change may also be helping to slow it—at least for now.

气候变化导致了绿色植物的生长。随着地球的升温，曾经那些太过寒冷不适合生长植被的地方，如今已经是植被的乐土了。因气候变化而多长的植被反过来也对气候产生了影响。在加利福尼亚，Lawrence Berkeley国家实验室，由Trevor Keenan领导的一个小组刚刚公布了他们的发现，并发布在在《自然通信》一杂志中：由气候变化所引起的植物生长也许可以缓解全球变暖―至少是可以缓解当前的变暖现象。

• chilly:adj.寒冷的

• hospitable:adj.好客的

• nature communication:自然通信

In 2014 humans pumped about 35.7bn tonnes of carbon dioxide into the air. That figure has been climbing sharply since the middle of the 20th century, when only about 6bn tonnes a year were emitted . As a consequence, the concentration of CO2 in the atmosphere has been rising too, from about 311 parts per million (ppm) in 1950 to just over 400 in 2015. Yet the rate at which it is rising seems to have slowed since the turn of the century. According to Dr Keenan, between 1959 and 1989 the rate at which CO2 levels were growing rose from 0.75ppm per year to 1.86. Since 2002, though, it has barely budged . In other words, although humans are pumping out more CO2 than ever, less of it than you might expect is lingering in the air.

2014年，全球二氧化碳的排放量达到了35.7bn吨。在二十世纪中叶时期每年只有60亿的二氧化碳排放量，但是从那之后，这一数字开始大幅攀升。结果大气中的二氧化碳浓度不断上升，从1950年的约百万分之311（ppm）到2015年超过百万分之400。然而，在二十到二十一世纪之交，上升速度似乎放缓了。据Keenan博士所说，从1959年到1989年，二氧化碳的增长速率从0.75ppm 上升到1.86。然而自2002以来，增长率就几乎没什么变化了。换句话说，尽管人类排放的二氧化碳量更大了，但空气中二氧化碳的含量却比人们想象中的要少。

• climbing sharply：大幅度地上升

• emit:v.排放

• budge:v.移动

• linger:v.徘徊

Filling the atmosphere with CO2 is a bit like filling a bath without a plug: the level will rise only if more water is coming out of the taps than is escaping down the drain. Climate scientists call the processes which remove CO2 from the air “sinks”. The oceans are one such sink. Photosynthesis by plants is another: carbon dioxide is converted , with the help of water and light energy from the sun, into sugars, which are used to make more plant matter, locking the carbon away in wood and leaves. Towards the end of the 20th century around 50% of the CO2 emitted by humans each year was removed from the atmosphere this way. Now that number seems closer to 60%. Earth’s carbon sinks seem to have become more effective, but the precise details are still unclear.

在大气中排放二氧化碳有点像在一个没有塞子的浴缸中注水：只有当进水比排水量水多的时候，水位才会上升。气候学家将空气中的二氧化碳去除过程称之为“吸存”。海洋是其中之一。植物的光合作用是其二：在水和太阳光能的帮助下，二氧化碳转化成能量，产生更多的植物物质，从而将碳储存在树木和叶子中。到二十世纪末，人类每年排放的约50%的二氧化碳通过该途径被吸收。现在这个数字将近到达60%。 碳汇 似乎变得更有效了，但具体细节尚未明确。

• 碳汇：碳汇，一般是指从空气中清除二氧化碳的过程、活动、机制。主要是指森林吸收并储存二氧化碳的多少，或者说是森林吸收并储存二氧化碳的能力。

• tap：n.水龙头

• convert:v.转化

• precise:adj.精确

Using a mix of ground and atmospheric observations, satellite measurements and computer modelling, Dr Keenan and his colleagues have concluded that faster-growing land plants are the chief reason. That makes sense: as CO2 concentrations rise, photosynthesis speeds up. Studies conducted in greenhouses have found that plants can photosynthesise up to 40% faster when concentrations of CO2 are between 475 and 600ppm.

Keenan博士和他的同事综合地质和大气的观察数据、结合卫星测量和电脑模型得出结论：快速生长的植物是碳汇效果增加的主要的原因，这一结论很合理：随着二氧化碳浓度的增长，光合作用也在加速。在温室实验室中进行的研究发现，当二氧化碳的浓度在475到600ppm时，植物光合作用的速度提高了40％。

• concentration: n.  浓度

For delegates at the latest round of UN climate talks, in Marrakech, that sounds like good news. But more vigorous photosynthesis is only slowing climate change. The effect is too small to reverse it. And it will not last, says Dr Keenan. Besides, there is more to growing plants than carbon dioxide. Take water: in a changing climate, wet bits of the world will probably become wetter while drier parts become drier. Extreme events— droughts and deluges —will intensify. Rainfall patterns may change, which could make some places less friendly to plants that now thrive there. And although plants benefit in the short term from extra CO2, they suffer when temperatures get too high.

对于刚刚召开的马拉喀什联合国气候谈判大会的各个代表来说，这项发现是个好消息。但是增加的光合作用只会减缓气候变化，效果过于微弱并不能彻底反转温室效应。Keenan博士表示，光合作用增加所带来的积极影响不会持久，除了植被的变化还有其他的副作用，以水为例:在变化的气候中，地球上潮湿的地区会更潮湿，干旱的地方干旱也会加剧。极端气候现象诸如干旱和洪水会变得更加频繁。降雨模式可能会发生改变，这可能导致某些地区原本生长旺盛的植物失去生机。尽管短期内植物可以吸收过量的二氧化碳，但是当气温过高时，植物也会因其受害。

• delegate:n. 代表

• deluge:n. 淹没

• intensify:v. 使增强

• thrive:v. 兴盛

There will be more complicated effects, too. Much of the greening has occurred in cold spots (see map). Yet while ice and snow reflect sunlight, vegetation soaks it up, so more greenery in the north will eventually lead to yet more warming. That, in turn, could release large quantities of methane —a potent but short-lived greenhouse gas—from thawing tundra . Elsewhere, higher temperatures could kill tropical forests. According to one estimate, for every degree of warming, tropical forests may release greenhouse gases equivalent to five years’ worth of human emissions.

这可能还会带来更复杂的影响。大部分的植被增加发生在寒冷的地方（如图所示）。当冰雪反射阳光时，植物会吸收光，所以北方绿地增加终将会导致更严重的气候变暖。这反而会使冻土带融化，释放更多的沼气―一种强烈不稳定的温室气体。 期待您的翻译，您可以将翻译留言到文章底部，第二天会有详细解析哦 。

• methane:n.沼气

• potent:adj. 有效的

• thawing tundra:融化的冻土带

• tropical:adj. 热带的

• emission:n. 排放物

Indeed, some researchers think the effects of global greening may already be fizzling out . Every few years a climatic phenomenon called El Niño sees the tropical Pacific Ocean warm substantially, which tends to raise temperatures around the world. The most recent Niño, in 2015-16, was a whopper . Corinne Le Quéré, a climate researcher at the University of East Anglia in Britain says that means the world’s plants may have, therefore, become a less potent carbon sink than they were in the period studied by Dr Keenan’s team. Global greening, then, offers only a little breathing space. Kicking the fossil-fuel habit remains the only option.

的确，一些研究人员认为全球植被增加带来的积极影响或许已经被抵消了。每隔几年，厄尔尼诺现象就会发生，这就可以有力表明太平洋的变暖，并导致了世界气候变暖。最近一次的厄尔尼诺现象发生在2025年到2016年间，规模巨大。英国东盎格利亚大学的一位气候研究员Corinne Le Quéré认为这意味着地球上的植物不再会像Keenan博士团队曾经研究的那样，碳汇效果不再明显。全球植被增加只是让我们缓了口气，想要扭转温室现象，彻底摆脱化石燃料供能才是我们唯一的出路。