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Geo-engineering
地球工程
Every silver lining has a cloud
曙光前面总有一片乌云
Jan 29th 2009
From The Economist print edition
Plans to engineer the climate may be less effective than had been hoped
气候控制工程远非预期中那样有效
IF PEOPLE can warm the Earth, they can probably cool it too. That is the idea behind geo-engineering, which holds that besides cutting the rate at which it is turning fossil fuels into climate-changing carbon dioxide, humanity should also consider planet-wide engineering projects intended to reduce the side-effects of this combustion. All sorts of ideas have been proposed, from filling the stratosphere with reflective particles to giant space-borne parasols designed to shade the Earth from the sun. The idea of such a technological last chance, even if it sounds implausible, is a secret comfort to many of those frustrated by the lack of progress around the world in cutting emissions of greenhouse gases. Two papers published this week suggest, though, that those hopes may be misplaced.
如果说地球变暖是由于人类活动造成的，那么人类也应该可以使地球凉下来。这就是地球工程的指导思想，人类在通过降低使用矿物燃料产生导致气候变化的二氧化碳之余，还能够通过一些遍及全球的工程来减轻燃料使用中（对环境）产生的副作用。人们为此想出了各种各样的方案，其中既有在平流层中喷洒反射性微粒，也有通过在空中设置一顶阳伞来遮挡阳光。尽管这些方案听上去难以置信，但对于那些致力于控制全球温室气体排放却仍然毫无进展的人们来说，这些方案无疑是一种神秘的慰藉。然而，本周发表的两篇文章指出，对于地球工程的期望可能只是一种奢望。
The first, by a group of researchers from Britain’s National Oceanography Centre, led by Raymond Pollard, looked at the idea of dumping iron in the oceans to promote huge blooms of phytoplankton—tiny algae that consume carbon dioxide as they grow. This approach has received a lot of interest. Though much of the carbon thus absorbed returns to the atmosphere when the plankton die, around 8-9% ends up locked away beneath the waves for decades or more. Dr Pollard’s paper, which appeared in Nature, outlined the results of an experiment that looked at the effects of iron on the growth of phytoplankton near the Crozet Islands in the Southern Ocean.
在{dy}篇文章中，由Raymond Pollard牵头的一组来自Britain’s National Oceanography Centre的研究者们对一项地球工程方案提出了自己的看法。该方案试图通过向海水中倒入铁来刺激某种浮游生物的生长，这种藻类在生长的过程中可以消耗二氧化碳。这一方案受到了众多的xx，尽管在这种浮游生物死亡后，它所吸收的二氧化碳会重新释放到大气中，但大约有8-9%的二氧化碳能被保留在海洋深处长达十年甚至更长的时间。Pollard博士在《Nature》上发表的文章中描述了他们在位于南海克罗泽群岛附近进行一项实验的结果，该实验目的在于检验铁对浮游生物生长的刺激作用。
Every year, as the days lengthen, the seas near these islands produce an enormous bloom of plankton, roughly the size of Ireland. Erosion of the islands dumps large quantities of iron in the water. The prevailing currents then carry most of this iron north, leaving the waters to the south with less. That makes the seas around the Crozet Islands an ideal natural laboratory. Dr Pollard and his colleagues found, as geo-engineers would hope, that phytoplankton blooms in the waters north of the islands were bigger and longer-lived than those to the south. More plankton means more carbon dioxide sucked from the air.
在每一年日照时间加长的时候，克罗泽群岛附近海洋中会产生大量的浮游生物，其面积甚至与岛屿的总面积相当。（海水）对岛屿的侵蚀使得大量的铁进入海水中。主要的洋流将这其中大部分的铁带往北方的海域，而南方海域中的铁含量则相对较少。这样的条件使得克洛泽群岛地区成为一个理想的自然实验室。Pollard博士和他的同事发现，北面海域中浮游生物的确比南面海域中的体型更加硕大，而且寿命也更长，这与地球工程中的预期一致。更多的浮游生物就意味着空气中更多的二氧化碳被吸收。
The researchers reckon that the extra iron boosted growth rates and carbon-dioxide consumption between two- and threefold. They also found the first evidence of a similar boost in the amount of carbon locked away in the deep ocean. But while the theory of iron fertilisation seems sound, the practice may be tricky: the team’s results suggest that geo-engineers have overestimated the amount of carbon removed per tonne of iron by between 15 and 50 times.
研究人员估算由铁导致的额外生长的浮游生物以及二氧化碳吸收量大约是原水平的2到3倍。他们还首次发现被保留在深海的二氧化碳增长量也大致处于同一水平。虽然研究结果显示由铁来控制二氧化碳理论上行得通，但是在实践中似乎并非行得通：他们指出地球工程师们对每公吨铁导致二氧化碳吸收量的估计过高，高估达15到20倍。
Similarly sobering conclusions are reached in the second paper, by Tim Lenton of the University of East Anglia and Naomi Vaughan of the Tyndall Centre for Climate Change Research, and published in Atmospheric Chemistry and Physics Discussions. This study attempts to rank the likely effectiveness of various geo-engineering proposals.
来自University of East Anglia的Tim Lenton和来自Tyndall Centre for Climate Change Research的Naomi Vaughan，在其发表于《Atmospheric Chemistry and Physics Discussions》的文章中得出了类似的客观结论。在他们的研究中，对几种地球工程方案成效进行了排序。
Because geo-engineering is a new field, the researchers chose to ignore trifles such as cost or practicality, and focused instead on the sheer physical limits on what can be done and how much good the different schemes would do. Top of the list is a solar shade, a gigantic umbrella in space that would shield the Earth from the sun’s rays. This is both the most effective option and the most “scalable”, since a hotter Earth would simply require a bigger or more opaque parasol.
由于地球工程是一个新兴领域，他们并没有将花项目成本、实用性等边缘因素列为考察的重点，他们重点xx这些方案实施时的物理限制因素以及在同一方面其他方案的表现。在他们排名表列xx的是一个太阳能保护伞方案，该方案计划在太空中放置一顶大伞来阻挡太阳射线。但考虑到逐渐升温的地球将会不断需要一顶张得更大伞或阻隔效果更好的伞，这个项目不仅效果{zj0}，而且也{zj1}“伸展性”。
The other ideas suffer from fundamental limits that stop them being scaled up indefinitely. Injecting sulphate particles into the stratosphere, for instance, would cool the Earth by reflecting more sunlight into space. (Nature has already shown that this concept can work, since volcanic eruptions that send sulphur-rich plumes into the stratosphere can temporarily alter the world’s climate.) However, Dr Lenton notes that the method becomes less effective as the atmosphere becomes more saturated with particles. At most, he reckons, the sulphate-injection approach could counteract half of the warming the world is expected to suffer over the next 100 years if carbon-dioxide emissions continue to rise unchecked.
另一项方案也由于一些根本上的限制使得其不可能无限的使用。向平流层喷洒硫酸盐颗粒，可以通过反射阳光达到降低地球温度的作用。（一些自然现象已经证实这一构想的正确，例如在火山喷发的时候，富含大量硫酸盐的烟流被送向平流层，从而暂时的改变全球气候）。但是，Lenton博士指出，随着喷向大气中微粒的逐渐饱和，这一做法的效果将逐渐减弱。根据Lenton博士估算，这一做法最多只能抵消一半的温室效应，而如果二氧化碳排放排放量持续无节制的增加，地球将会在未来的100年内继续遭受温室效应之苦。
Other options seem even less effective. Encouraging cloud formation over the oceans by spraying seawater into the air would be roughly as helpful as pumping the stratosphere full of particles. Its effects, though, would be geographically patchy. And dumping nutrients such as iron into the sea would be only one-sixth as effective as either sulphate injection or promoting the formation of clouds.
其他方案的效果显得更加难以信服。一项方案中将海水喷向控制以促使海洋上方云团的形成，以期望达到向平流层喷洒微粒类似的效果。 这项方案效果的实现在地理上还存在一些漏洞。而向海水中倾倒铁一类的营养物质的效果仅仅是喷洒硫酸盐微粒或促使云团形成效果的六分之一。
Moreover, effectiveness is only one way to rank the ideas. In theory, a solar shade could provide any amount of cooling, but the researchers estimate that it would have to have an area of 4.1m square kilometres (half the size of Brazil) to offset half the warming expected over the next century, assuming no cuts in carbon-dioxide emissions occur. A polite critic of such a plan might describe it as “ambitious”. Sulphate particles, meanwhile, survive only a few years in the atmosphere. For the sulphate-injection method to remain effective they would need to be replenished constantly for centuries—longer than the lifetime of most countries.
更为重要的是，方案的效果只是评价方案的一个指标。理论上讲，一个太阳能护罩可以起到很大的降温作用，但是如果二氧化碳排放量没有减少的话，研究人员预计这将需要一个4100万平方千米（相当于半个巴西）的防护罩才能在下个世纪减弱一半的温室效应。客气的说，这个方案可谓相当的“霸道”。而硫酸盐微粒方案只能在短暂的几年内有效。如果要维持它的效果，则需要在几个世纪的时间里不断补充硫酸盐微粒，这个时间远远长于大多数的国家存在的时间。
Then there are the side-effects. Any geo-engineering project would necessarily be enormous, and would therefore cause plenty of disruption to ecosystems. Plans to suck carbon from the air by growing trees conflict with the need to grow crops. Creating gigantic algal blooms risks using up all the oxygen in large parts of the ocean, killing anything else that lives there. These sorts of things are unlikely to go down well with environmentalists. Indeed, a group of researchers hoping to conduct more experiments on ocean fertilisation was recently ordered to stop by the German government. Ministers were worried that the experiment might have been illegal under international laws designed to protect marine wildlife, although they eventually gave the go-ahead. When it comes to the environment, there are no perfect answers.
除了以上的问题，地球工程还存在一些副作用。任何的地球工程项目必然是巨大的工程，这就必然会破坏一些生态系统。计划用来吸收二氧化碳而种植的树木将会与种植粮食相冲突。海藻大量繁殖将会耗尽大部分海洋中氧气，进而杀死海洋中的生物。这些后果都是不受环境保护主义者欢迎的东西。事实也确实如此，近来一些研究人员希望对被德国政府叫停的海洋肥沃化进行更多的实验研究。英国首相曾担忧这样的研究活动会触犯旨在保护海洋野生生物的国际法律，但他们最终还是得到了批准。当涉及到环境问题时，永远没有一个xx的解决方案。 |
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