A Such is our dependence on fossil fuels, and such is the volume of carbon dioxide already released into the atmosphere, that many experts agree that significant global warming is now inevitable. A. 人类对于化学燃料的过度依赖，以及空气中二氧化碳排放量的剧增，让专家们一致认为，大规模的全球变暖已在所难免。 They believe that the best we can do is keep it at a reasonable level, and at present the only serious option for doing this is cutting back on our carbon emissions. 专家们的意思是，我们最好能将碳排放量保持在一个合理的水平，而目前我们唯一需要认真做到的就是减少碳排放。 But while a few countries are making major strides in this regard, the majority are having great difficulty even stemming the rate of increase, let alone reversing it. 虽然一些国家在这一方面取得了显著的成果，但大多数国家仍然做不到降低碳排放的增长率，更别说减排了。 Consequently, an increasing number of scientists are beginning to explore the alternative of geo-engineering - a term which generally refers to the intentional large-scale manipulation of the environment. 因此越来越多的科学家开始寻找第二个方案，地球工程—— 一个用来整体描述全球范围内环境管理的术语。 According to its proponents, geo-engineering is the equivalent of a backup generator: if Plan A - reducing our dependency on fossil fuels - fails, we require a Plan B, employing grand schemes to slow down or reverse the process of global warming. 支持者们声称，地球工程就等同于一个后备选项，如果减排的A计划失败了，我们就启动B计划，采取全球性措施来减缓或扭转全球变暖的趋势。

B Geo-engineering has been shown to work, at least on a small localised scale. B.地球工程在小范围内已经卓有成效。 For decades, May Day parades in Moscow have taken place under clear blue skies, aircraft having deposited dry ice, silver iodide and cement powder to disperse clouds. 几十年以来，蓝天白云笼罩下的莫斯科的五一游行每年都在进行，飞机已经在到处播撒干冰、碘化银和水泥粉来驱散云层。 Many of the schemes now suggested look to do the opposite, and reduce the amount of sunlight reaching the planet. 现行的很多规划都是要反其道而行之，减少到达地球的太阳光 The most eye-catching idea of all is suggested by Professor Roger Angel of the University of Arizona. 。来自亚利桑那大学的罗杰·安吉尔教授提出了目前最吸睛的观点。 His scheme would employ up to 16 trillion minute spacecraft, each weighing about one gram, to form a transparent, sunlight-refracting sunshade in an orbit 1.5 million km above the Earth. 他计划使用16万亿、重约1克的微型飞船，在距离地球150万千米的轨道上运行，形成一个透明的可以反射阳光的天棚。 This could, argues Angel, reduce the amount of light reaching the Earth by two per cent. 安吉尔认为这样一来，就可以将到达地球的太阳光减少2%。

C The majority of geo-engineering projects so far carried out - which include planting forests in deserts and depositing iron in the ocean to stimulate the growth of algae - have focused on achieving a general cooling of the Earth. C.& 目前开展的主要的地球工程项目包括在沙漠中种植绿树以及在大海里投放铁块以促进藻类生长，这些努力都集中于让地球降温。 But some look specifically at reversing the melting at the poles, particularly the Arctic. 但是有些项目却着眼于扭转极地地区尤其是北极冰盖的融化。 The reasoning is that if you replenish the ice sheets and frozen waters of the high latitudes, more light will be reflected back into space, so reducing the warming of the oceans and atmosphere. 这是因为如果能留住高纬度地区的冰层和冻水，更多的阳光就会被反射回太空，因而也就降低了海洋和大气的气温。

D The concept of releasing aerosol sprays into the stratosphere above the Arctic has been proposed by several scientists. D.有科学家曾提出将气雾剂喷到北极上方的空气中的办法。 This would involve using sulphur or hydrogen sulphide aerosols so that sulphur dioxide would form clouds, which would, in turn, lead to a global dimming. 气雾剂的成分主要是硫或氢化硫，这样一来二氧化硫就会形成云层，因而就会实现全球变暗。 The idea is modelled on historic volcanic explosions, such as that of Mount Pinatubo in the Philippines in 1991, which led to a short-term cooling of global temperatures by 0.5℃. 这个点子来源于历史上火山爆发的案例，例如，1991年位于菲律宾群岛的皮纳图博火山突然爆发，导致全球温度短期内降低了0.5度。 Scientists have also scrutinised whether it's possible to preserve the ice sheets of Greenland with reinforced high-tension cables, preventing icebergs from moving into the sea. 同时，科学家们也在思考是否有可能使用高压电缆来保护格林兰岛岛冰层，不让冰山融化到海水中。 Meanwhile in the Russian Arctic, geo-engineering plans include the planting of millions of birch trees. 而在俄罗斯的北极地区，地球工程计划在此种植成千上万的桦树。 Whereas the region's native evergreen pines shade the snow and absorb radiation, birches would shed their leaves in winter, thus enabling radiation to be reflected by the snow. 尽管这一地区的常青树松树也会给雪山带来阴凉，吸收阳光辐射，但桦树在冬天才落叶，因而能让雪地来反射光辐射。 Re-routing Russian rivers to increase cold water flow to ice-forming areas could also be used to slow down warming, say some climate scientists. 另外，一些气候学家还提出一个缓解全球变暖的办法，就是改变俄罗斯境内河流的路径，增加冷水朝向结冰地区的流量。

E But will such schemes ever be implemented? E. 但是这些想法会不会真正实施呢？ Generally speaking, those who are most cautious about geo-engineering are the scientists involved in the research. 整体说来，对于地球工程持谨慎态度的都是正在做科研的科学家。 Angel says that his plan is 'no substitute for developing renewable energy: the only permanent solution'. 安吉尔认为他的计划“不能取代对可再生能源的开发，人家才是唯一的永久的解决方案”。 And Dr Phil Rasch of the US-based Pacific Northwest National Laboratory is equally guarded about the role of geo- engineering: 'I think all of us agree that if we were to end geo-engineering on a given day, then the planet would return to its pre-engineered condition very rapidly, and probably within ten to twenty years. 美国太平洋西北国家实验室的菲尔·拉希博士同样看重地球工程的作用，他说：我认为我们都认可的一点是如果我们注定在某一天要终止地球工程，那么也许十到二十年的时间里，地球将很快倒退到前工程时代， That's certainly something to worry about.' 这才是我们应当真正担心的问题啊！”

F The US National Center for Atmospheric Research has already suggested that the proposal to inject sulphur into the atmosphere might affect rainfall patterns across the tropics and the Southern Ocean. F. 美国太空研究中心已经暗示，将硫喷射到大气层的计划可能会影响热带地区和南海的降雨模式。 'Geo-engineering plans to inject stratospheric aerosols or to seed clouds would act to cool the planet, and act to increase the extent of sea ice,' says Rasch. ' 拉希指出，“地球工程的这一在平流层喷射气雾或者人造云层的计划会让地球降温，也会让海面冰层增长。 But all the models suggest some impact on the distribution of precipitation.' 但是所有的这些举动都会对降雨对分布产生一定的影响。”

G 'A further risk with geo-engineering projects is that you can "overshoot",' says Dr Dan Lunt, from the University of Bristol's School of Geophysical Sciences, who has studied the likely impacts of the sunshade and aerosol schemes on the climate. G. “另一个地球工程的潜在风险就是过犹不及，”来自布里斯托大学地球物理学院的丹·伦特博士如是说，伦特博士专注于阴凉和喷雾剂计划对气候的影响研究。 'You may bring global temperatures back to pre-industrial levels, but the risk is that the poles will still be warmer than they should be and the tropics will be cooler than before industrialisation.' “我们可能会让全球的气温回归到前工业时代的水平，但是风险却在于极地地区会比平常气温更高，而热带地区则会比工业化之前的气温更低。” To avoid such a scenario, Lunt says Angel's project would have to operate at half strength; all of which reinforces his view that the best option is to avoid the need for geo-engineering altogether. 为了避免这样的情况出现，伦特博士指出，安吉尔的项目可能只能执行一半，而其实他的观点就是最好不要实施地球工程了吧。

H The main reason why geo-engineering is supported by many in the scientific community is that most researchers have little faith in the ability of politicians to agree - and then bring in - the necessary carbon cuts. H. 科学界对地球工程投赞成票的依然不计其数，其主要原因还是大多数科研人员其实对政治家们对减排的认可和实践信心不足。 Even leading conservation organisations see the value of investigating the potential of geo-engineering. 即使是领头的环保组织都能预见地球工程的潜在价值。 According to Dr Martin Sommerkorn, climate change advisor for the World Wildlife Fund's International Arctic Programme, 'Human-induced climate change has brought humanity to a position where we shouldn't exclude thinking thoroughly about this topic and its possibilities.' 世界野生动物基金会旗下的国际北极项目的气候变化顾问马丁·索玛科恩博士认为，“人为导致的气候变化已将人性放置到一个我们不得不全面思考这个问题以及它有可能导致的后果的局面。”