Orbiting giant sunshade gets thumbs down from climate scientists

Unconventional schemes for tackling global warming by installing a giant sunshade in orbit, sowing the seas with iron and scattering sulphur into the upper atmosphere are set to be bluntly rejected by UN experts this week.
The oddball initiatives are being fostered by "geo-engineers" - scientists who say headway to reduce the fossil-fuel pollution which drives global warming is so ludicrously slow that bold new ideas are needed to avert climate catastrophe.
Among solutions they sketch is a giant network of tilted mirrors, deployed in orbit, that would deflect some of the sunlight Earth receives.
Another idea is to sow particles of sulphur dioxide (SO2) particles in the upper atmosphere to reflect sunlight back into space. Another is to "fertilise" the seas with iron so that surface algae sucks up carbon dioxide (CO2) from the air.
The goal of these and other schemes is to offset the warming effect of greenhouse gases and, at the very least, buy time for an effective deal for slashing carbon pollution.
The world's leading climate scientists are to meet in Bangkok from Monday to set out ways of minimising the damage caused by climate change.
Their report on ways of reining in the greenhouse gases that trap heat and fuel climate change will be released on Friday.
A draft of the Intergovernmental Panel on Climate Change (IPCC) document shows that the meeting will agree that the window of opportunity is narrowing.
What happens over the next two to three decades "will determine to a large extent the long-term global mean temperature increase and the corresponding climate-change impacts that can be avoided," according to the draft.
But it pours scorn on geo-engineering as a means of tackling the problem, branding its approaches as hypothetical, tarred with risk and carrying unknown economic costs.
"Geo-engineering options ... remain largely speculative and with the risk of unknown side effects," it says.
"Reliable cost estimates for these options have not been published."
-AFP
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