By Joseph Milton, FT science intern
Simulations run by a team at the University of Bristol suggest that the melting of the Greenland ice sheet could be prevented by reflecting sunlight from the earth’s surface, a geoengineering technique.
Geoengineering offers radical solutions to climate change, involving large-scale alterations to the environment, directly affecting the climate. Discussion of these potentially risky procedures is increasingly common as many scientists reach the conclusion that CO2 emission reduction targets are not being met, and are unlikely to be. The Royal Society recently invited a panel of scientists to look into the subject and produce a report: Geoengineering the climate: science, governance and uncertainty.
The research at Bristol, led by Peter Irvine and published today in Environmental Research Letters, found that the temperature of the planet could be reduced to pre-industrial levels, saving the ice sheet, by reflecting 4.2 per cent of incident sunlight back into space.
But reflecting such a high percentage of sunlight, while doing nothing to reduce atmospheric CO2 levels, could reduce rainfall and change weather patterns, so the team also investigated reflecting 2.5 per cent of sunlight. They found this reduced the undesired side effects, but still cooled the planet enough to avoid the collapse of the ice sheet.
The Bristol team suggest sunlight could be deflected using geoengineering techniques known as solar radiation management. One option is the use of space reflectors – trillions of tiny reflective particles at the Lagrange point, the point in space at which the Earth and the Sun’s gravitational fields cancel each other out.
Professor Peter Cox at the University of Reading, who worked on the Royal Society report, says it might work: “It would be like just turning the sun down a bit.” But obviously there are technical considerations. As Professor Joanna Haigh of Imperial College, another of the report’s authors, points out: “The costs and the timescales involved would be absolutely enormous.” Neither thinks this technique is feasible in the near future.
Another option suggested by the Bristol team involves the addition of sulphate particles to the atmosphere, where they would reflect solar radiation. Prof. Cox says this is more difficult to rule out than he had imagined before the report was written, but Prof. Haigh is less convinced: “Who knows what the knock-on effects would be?” she says.
Solar radiation management is one of two broad categories of geoengineering techniques. The second is carbon dioxide removal, recently suggested as a possible complement to mitigation actions by Rajendra Pachauri, head of the Intergovernmental Panel on Climate Change.
Removing CO2 from the atmosphere would be a better long-term solution to global warming, as it would tackle not just global temperatures but other problems associated with high levels of greenhouse gases too, such as ocean acidification. But it would be very slow to affect the climate. On the other hand, the effects of reflecting sunlight could be seen within a few years.
Peter Irvine stressed that geoengineering should only be regarded as an emergency response: “It is no substitute for reductions in the emission of CO2,” he said.