Two years ago John Latham, an atmospheric scientist from the U.S. National Center for Atmospheric Research in Boulder, Colorado, and his colleagues put forward a plan to whisk up seawater to encourage cloud formation in the lower atmosphere, thereby reflecting radiation back into space.
"All of us recognize that geo-engineering seems increasingly likely to be the only route to staving off a cataclysm in the short term before new, clean energy sources are developed sufficiently," Latham said.
He thinks that Crutzen's idea is feasible, but he says further investigation is needed.
"This idea could help to hold the temperature constant, but we need to examine some of the potential adverse ramifications," Latham said.
Crutzen admits that there is a risk of the sulfur becoming a health hazard if it rained back down on Earth.
In addition there could be an increase in damage to the ozone layer and a whitening of the sky.
"If things go wrong during the experiment, then [we would] stop," he said. "In a few years the atmosphere [will] return back to its earlier condition."
On the upside, sunsets and sunrises would become more spectacular.
Crutzen calculates that launching enough sulfate to have an effect for two years would cost between 25 billion and 50 billion U.S. dollars, about $25 to $50 per head in the developed world.
There may still be time for nations to reduce greenhouse emissions enough to make such extreme measures unnecessary, Crutzen concludes, but no one can know for certain.
"We don't know the future, so this question is impossible to answer," he said.
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