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Is there a Plan B?

THE WORLD may have to fall back on little-understood and potentially dangerous "geoengineering" techniques to stem global warming if December's climate-change talks fail, says the UK's Royal Society (RS). An RS study, Geoengineering the climate: Science, governance and uncertainty, says unless future measures to cut greenhouse-gas emissions are much more successful than those taken so far, some little-tested forms of more radical intervention may be needed in the longer term. The most promising of these are Carbon Dioxide Removal (CDR) and Solar Radiation Management (SRM).

CDR could take three main forms: capturing CO2 from the ambient air; enhanced weathering, which uses chemical reactions involved in rock weathering to reduce CO2 levels in the air; and increased afforestation to enable more CO2 to be absorbed by vegetation. However, the society says, the first two techniques have yet to be shown to be practical or cost effective, while afforestation would create land-use conflicts.

While removing CO2 from the air would be the preferred method of tackling global warning, as it deals directly with the root cause of the problem, more drastic measures, such as SRM, may be required, according to the report. It concluded that the use of stratospheric aerosols to reflect some of the sun's energy away from the earth, therefore lowering temperatures, would be feasible and that studies of the effects of past volcanic eruptions, which have thrown dust into the atmosphere, have suggested it could be effective.

But while this could be a relatively low cost and rapidly deployed technique, the society said the effects of using aerosols could produce unwelcome side effects, such as the depletion of stratospheric ozone. It would also fail to address the underlying issue of increasing CO2 levels and ocean acidification. The society also investigated ideas such as shields in space to deflect the sun's rays, but said they would be prohibitively expensive at the moment.

Despite the difficulties, John Shepherd, chair of the RS team that complied the report, wants to see more funding for these and other possible measures, calling on the UK government to invest £10m a year in geoengineering research.

"It is an unpalatable truth that unless we can succeed in greatly reducing CO2 emissions we are headed for a very uncomfortable and challenging climate future, and geoengineering will be the only option left to limit further temperature increases," he said on launching the report. "Our research found that some geoengineering techniques could have serious unintended and detrimental effects on many people and ecosystems – yet we are still failing to take the only action that will prevent us from having to rely on them."

Continued uncertainty over the potential for success at the UN-backed climate talks, which start in Copenhagen in November, adds piquancy to his remarks. UN officials have been working hard to convince Western nations, especially the US, that tougher emissions regulations in a Copenhagen agreement would not simply result in more of their industries relocating to parts of the world where emissions requirements remain less onerous. But China and other developing nations remain reluctant to agree to pay for big cuts in their own emissions to deal with a problem they regard as having been caused mainly by the West.

Shepherd put the chances of emissions cuts being able to keep global warming below 2?C at no more than 50%. "It is essential that we strive to cut emissions now, but we must also face the very real possibility that we will fail," he said. If that happens then there may be little choice but to implement some of those Plan B technologies about which so little is known.

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