Can we use technology to halt climate change? (Image: Gaetan Charbonneau / Workbook Stock / Getty)

The effects of geoengineering could be worse than climate change, so we need to do our homework rather than assume it can stave off disaster.

OUR profligate greenhouse emissions are creating problems of planetary proportions for our descendants. Even in the best-case scenario, if we make drastic cuts in emissions soon, sea levels will rise by anything from 10 metres to 25 metres over the next few thousand years.

Faced by the loss of so much precious coastal land, it seems quite plausible that our descendants will resort to some kind of mega-project to cool the planet and stop the ice sheets melting. If so, why not do it sooner rather than later? It might save countless lives, not to mention the myriad species otherwise doomed to extinction.

There is no shortage of grand ideas for geoengineering. We could pump cooling sulphur into the atmosphere to disperse incoming sunlight, or generate reflective clouds by spraying seawater heavenwards from special ships. We might even launch an almighty flotilla of parasols into space to shade our planet from the sun.

The problem with all of these schemes is that we have little clue whether they would work. Some of the best evidence so far comes from the cataclysmic eruption of Mount Pinatubo in 1991, which obligingly conducted a large-scale experiment for us on the effect of injecting sulphur into the upper atmosphere. From a global cooling perspective, the results were encouraging: temperatures sank temporarily by up to 0.5 °C. It remains unclear, however, whether the …