Slim chance of dimming sun

OSLO: The idea of spraying a haze of sun-dimming chemicals high above Earth as a quick way to slow global warming faces so many obstacles it may not be feasible, a leaked draft UN report says.

The UN review of a planetary sunshade, mimicking how a big volcanic eruption can cool the planet with a veil of debris, is part of a broad study of climate technologies ordered by almost 200 nations in the 2015 Paris Agreement.

Proposals by scientists to spray chemicals high in the atmosphere from planes have attracted more attention since Paris as a relatively cheap fix, costing perhaps $1 billion (R12bn) to $10bn a year.

But such geo- engineering might be “economically, socially and institutionally infeasible”, according to the draft on the risks of droughts, floods, heat waves and storms.

The draft, by the Intergovernmental Panel on Climate Change (IPCC) about ways to limit warming to 1.5°C above pre-industrial times, is due for publication in October.

It could still change sub- stantially, the IPCC said.

Problems with “solar radiation management” include testing and working out rules for a technology that could be deployed by a single nation, or even a company, and might disrupt global weather patterns.

It “would result in an ‘addiction problem’; once started, it’s hard to stop”, the draft says. A halt after several years could lead to a jump in temperatures because greenhouse gases would continue to build up.

David Keith, faculty director of Harvard University’s solar geo-engineering research programme, which is working for a tiny outdoor experiment to dim sunshine, said there was a misguided “taboo” against examining the technology.

“We need a serious research effort to understand its risks and potential benefits. Then we will be able to write informed assessments,” he said.

But many scientists are sceptical. “To deploy it safely would take many decades,” said Myles Allen, a professor of geosystem science at Oxford University. – Reuters

PICTURE: REUTERS A plan to weaken the sun’s impact on earth, to combat climate change, might never see the light of day.