段落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. 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. 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. 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. 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.

我们对化石燃料的依赖如此之深，大气中已经释放出的二氧化碳量如此之大，以至于许多专家都同意，全球变暖不可避免。他们认为，我们所能做的最好办法就是将其控制在一个合理的水平，目前唯一严肃的选择就是减少碳排放。然而，虽然一些国家在这方面取得了重大进展，但大多数国家在减缓增长速度，更不用说逆转它了，都遇到了很大困难。因此，越来越多的科学家开始探索地球工程的替代方案，地球工程一词通常指的是有意地对环境进行大规模操纵。根据其支持者的说法，地球工程相当于备用发电机：如果A计划——减少对化石燃料的依赖——失败了，我们需要B计划，采用宏大的方案来减缓或逆转全球变暖进程。

段落B

Geo-engineering has been shown to work, at least on a small localised scale. 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. Many of the schemes now suggested look to do the opposite, and reduce the amount of sunlight reaching the planet. The most eye-catching idea of all is suggested by Professor Roger Angel of the University of Arizona. 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. This could, argues Angel, reduce the amount of light reaching the Earth by two per cent.

地球工程已经被证明在小范围内是有效的。几十年来，莫斯科的五一游行一直在晴朗的蓝天下举行，飞机向云层中喷洒干冰、碘化银和水泥粉末以驱散云团。现在提出的许多方案的目标正好相反，即减少到达地球的阳光量。其中最引人注目的想法是亚利桑那大学的罗杰·安吉尔教授提出的。他的方案将利用多达16万亿个质量约为一克的微型航天器，在距离地球150万公里的轨道上形成一个透明的、折射阳光的遮阳板。安吉尔认为，这可以减少到达地球的光线量达百分之二。

段落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. But some look specifically at reversing the melting at the poles, particularly the Arctic. 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.

到目前为止，大多数地球工程项目都集中在实现地球的普遍降温上，其中包括在沙漠中种植森林和在海洋中投放铁来促进藻类生长。但有的则专门研究逆转极地的融化，尤其是北极。他们的理论是，如果你重新补充高纬度地区的冰盖和冻结水域，就会有更多的光线反射回太空，从而减少海洋和大气的变暖。

段落D

The concept of releasing aerosol sprays into the stratosphere above the Arctic has been proposed by several scientists. 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. 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℃. 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. Meanwhile in the Russian Arctic, geo-engineering plans include the planting of millions of birch trees. 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. 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.

一些科学家提出了在北极上层大气层释放气溶胶喷雾的概念。这将涉及使用硫或硫化氢气溶胶，使二氧化硫形成云团，进而导致全球变暗。这个想法是以历史性的火山爆发为模板，比如1991年菲律宾的皮纳图博火山喷发，这导致全球气温短期内降低了0.5℃。科学家还研究了使用加固的高张力缆绳来保护格陵兰冰盖，防止冰山进入海洋的可能性。与此同时，在俄罗斯北极地区的地球工程计划中，包括种植数百万棵桦树。该地区的本土常绿松树为雪提供了阴影和吸收了辐射，而桦树冬天会脱叶，从而使辐射能够被雪反射。一些气候科学家还提出改道俄罗斯河流，增加冷水流入形成冰的区域，以减缓变暖。

段落E

But will such schemes ever be implemented? Generally speaking, those who are most cautious about geo-engineering are the scientists involved in the research. Angel says that his plan is ‘no substitute for developing renewable energy: the only permanent solution’. 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. That’s certainly something to worry about.’

但是，这些方案是否会被实施呢？总体上说，对地球工程最谨慎的是从事研究的科学家们。安吉尔表示，他的计划“不能替代可再生能源的开发：唯一的永久解决方案”。美国太平洋西北国家实验室的菲尔·拉什博士对地球工程的作用也持谨慎态度：“我认为我们都同意，如果我们某天停止地球工程，那么地球将迅速恢复到工程之前的状态，可能在十到二十年内。这确实是令人担忧的。”

段落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. ‘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. ‘But all the models suggest some impact on the distribution of precipitation.’

美国大气研究中心已经提出，将硫注入大气层可能会影响热带和南大洋的降雨模式。“地球工程计划注入平流层气溶胶或播种云团将导致地球冷却，增加海冰的范围，”拉什说，“但所有模型都表明会对降水分布产生一定影响。”

段落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. ‘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.’ 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.

布里斯托尔大学地球物理科学学院的丹·伦特博士对遮阳板和气溶胶方案对气候的可能影响进行了研究，他说：“地球工程项目的另一个风险是可能‘超调’。你可能会将全球温度恢复到工业化前的水平，但风险是极地仍然比应有的温暖，而热带地区将比工业化前更凉。”为了避免这种情况，伦特表示，安吉尔的项目必须以一半的强度运行；所有这一切都加强了他的观点，即最好的选择是避免完全需要地球工程。

段落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. Even leading conservation organisations see the value of investigating the potential of geo-engineering. 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.’