The threat of devastating climate change is now so great that some scientists say it is time to investigate a Plan B — geo-engineering on a planetary scale. Such methods of altering the world's climate may become necessary, they say, unless emissions of greenhouse gases fall within five years.
Ideas that were once the realm of science fiction — such as creating artificial trees to absorb carbon dioxide, or reflecting sunlight away from the Earth — are coming under serious scrutiny as temperatures and CO² emissions continue to rise. The issue has become so pressing that the Royal Society, Britain's national academy of science, is preparing a report on the feasibility of geo-engineering. Brian Launder, one of its contributors, said that without CO² reductions or geo-engineering, "civilisation as we know it will end within our grandchildren's lifetime".
Launder, a professor of mechanical engineering at Manchester University, reckons that extracting carbon from the atmosphere would be too slow a process to prevent significant warming. In his view "the only rational scheme is to reduce the amount of sunlight reaching earth and to reflect back more of it".
One method is to make clouds brighter — especially in the Pacific where the ocean temperature has great influence on world climate. "If these clouds can be brightened so you increase the sunlight reflected, it looks as though that could be enough ... to prevent most of the effects of global warming," said Launder.
Stephen Salter of Edinburgh University is probing how ships could spray sea water droplets into the atmosphere where they would evaporate, leaving tiny salt crystals to rise into the clouds. The crystals would act as "nuclei" around which water vapour could condense and thus raise the clouds' reflective power, bouncing more of the sun's energy back into space. Critics warn that although such schemes might lower temperatures swiftly, they must be maintained for long periods and the side-effects are unknown.
