An idea by the father of the H-bomb to slow global warming by sowing the stratosphere with light-reflecting particles could wreck the weather system in the tropics, a study says.
The scheme may benefit northern Europe and parts of Asia. But, around the equator, rainfall patterns would be disrupted, potentially drying up tropical forests in South America and intensifying droughts in Africa and Southeast Asia.
"The risks from this kind of geo-engineering are huge," said Andrew Charlton-Perez, a meteorologist at Britain's University of Reading.
In 1997, US nuclear physicist Edward Teller and other scientists suggested spreading sulphate particles into the upper atmosphere, reflecting some sunlight back into space to attenuate the Earth-warming greenhouse effect from fossil fuels.
This sunscreen - similar to the cooling effect from ash spewed by volcanic eruptions - would be cheaper than switching out of coal, gas and oil which cause the global warming problem, they said.
The idea is a favourite among geo-engineers, who nevertheless concede that manipulating the climate system on a planetary scale should be a last-ditch option.
In a paper published in the journal Environmental Research Letters, the British scientists said it would take a staggering volume of particles, called aerosols, to reverse warming.
"To reduce global temperatures enough to counter effects of global warming would require a massive injection of aerosol," said Angus Ferraro at the University of Exeter, southwestern England.
Each year, it would require the equivalent of five times the volume of ash disgorged by Mount Pinatubo in 1991 - the biggest volcanic eruption in the last quarter of a century.
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