US urges scientists to block out sun

THE US wants the world's scientists to develop technology to block sunlight as a last-ditch way to halt global warming.

It says research into techniques such as giant mirrors in space or reflective dust pumped into the atmosphere would be "important insurance" against rising emissions, and has lobbied for such a strategy to be recommended by a UN report on climate change, the first part of which is due out on Friday).

The US has also attempted to steer the UN report, prepared by the Intergovernmental Panel on Climate Change (IPCC), away from conclusions that would support a new worldwide climate treaty based on binding targets to reduce emissions. It has demanded a draft of the report be changed to emphasise the benefits of voluntary agreements and to include criticisms of the Kyoto Protocol, which the US opposes.

The final report, written by experts from across the world, will underpin international negotiations to devise an emissions treaty to succeed Kyoto, the first phase of which expires in 2012. World governments were given a draft of the report last year and invited to comment.

The US response says the idea of interfering with sunlight should be included in the summary for policymakers, the prominent chapter at the front of each panel report. It says: "Modifying solar radiance may be an important strategy if mitigation of emissions fails. Doing the R&D to estimate the consequences of applying such a strategy is important insurance that should be taken out. This is a very important possibility that should be considered."

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Possible techniques include putting a giant screen into orbit, thousands of tiny, shiny balloons, or microscopic sulfate droplets pumped into the high atmosphere to mimic the cooling effects of a volcanic eruption. The IPCC draft said such ideas were "speculative, uncosted and with potential unknown side-effects".

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It also complains that overall "the report tends to overstate or focus on the negative effects of climate change". It also wants more emphasis on responsibilities of the developing world.

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Professor Schneider said he was concerned the increase was more likely to be three degrees or higher, with a 10 per cent chance of a six-degree rise by the end of the century.

"Hell, we buy fire insurance based on a 1 per cent chance," he said. "If we're going to be risk averse … we cannot dismiss the possibility of potentially catastrophic outliers and that includes Greenland and West Antarctica [ice sheets breaking up], massive species extinctions, intensified hurricanes and all those things. "There's at least a 10 per cent chance of that. And that to me for a society is too high a risk … My value judgement when you're talking about planetary life support systems is that 10 per cent, my God, that's Russian roulette with a Luger."

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