麻豆传媒

Save the planet vs Look after future generations

The pressure is on. If we want to save the planet from the worst effects of climate change, we need to get our greenhouse gas emissions to zero by 2070 鈥� a target that requires immediate and drastic action. But our unbreakable addiction to fossil fuels makes this goal seem more and more unreachable. So what if there were another solution, some quick techno-fix that could let us burn our fuel but not our planet?

Enter geoengineering: large-scale manipulations of the planet designed to clean up our mess. The ideas range from sucking carbon dioxide out of the atmosphere to deploying a stratospheric parasol that would bounce the sun鈥檚 warming rays back out into space. Some have been field-tested, or soon will be. But while most climate researchers agree geoengineering makes sense as a last resort, we need to ask: do we have the right to interfere with the planet on this scale?

The answer might seem obvious: we鈥檝e already done it. By chucking billions of tonnes of greenhouse gases into the atmosphere, humanity has put the planet鈥檚 thermostat on turbo-boost, melted the Arctic, and altered the seasons, large-scale weather systems and the ocean鈥檚 acidity. Why should reversing that be any different?

Opinions vary. 鈥淎 strict consequentialist would argue that there is no ethical difference because what is right is determined solely by the outcome,鈥� says Steve Rayner, a climate policy researcher at the University of Oxford. 鈥淗owever for most other ethical viewpoints, motives matter. They certainly matter in law.鈥�

To John Shepherd of the University of Southampton, UK, who led a Royal Society working group on geoengineering, the risks need to be put in context: 鈥淚 find it hard to see that attempting to ameliorate climate change deliberately should be unacceptable in principle, so long as it was done carefully and cautiously, and with an exit strategy in place鈥�.

The various proposals carry different risks for different people. One contender involves covering vast areas with vegetation in order to suck CO₂ out of the skies and then be burned as fuel 鈥� with the resulting emissions buried deep underground. It may sound promising, but the new forests would have to compete for land with food crops, probably in tropical countries that have contributed least to global warming and will suffer most from it.

Sunshades also come with risks. Kevin Trenberth and Aiguo Dai of the US National Center for Atmospheric Research in Colorado looked at past mega-volcano eruptions, which release particles that reflect light in a similar way to proposed sunshades. They found that these events caused a marked decrease in precipitation, particularly in the tropics. Computer models have since confirmed that artificial sunshades would rapidly lower regional temperatures but also change rainfall patterns, resulting in poor harvests and the risk of drought.

Legacy is another major ethical concern. What goes up must come down and sunshades, like volcanic dust, will eventually be rained out. In the meantime, our continued appetite for fossil fuels would cause greenhouse gases to pile up in the atmosphere. If a future generation decided to stop maintaining the sunshade, the world would be hit with the full force of the resulting climate change. In the space of a few years, global temperatures would shoot up to where they should have been all along. The consequences for humanity could be disastrous.

Silver bullet, then, or Russian roulette? It may be that the only real solution is to find another one.

This article appeared in print under the headline 鈥淪hould we鈥� Engineer earth?鈥�