No man-made solution to sea-level rise
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COMMENTS 
Even the most extreme geo-engineering approach will not stop sea levels from rising because of climate change, a study suggests
New research says that as many as 150 million people could be affected the world over as ocean levels increase by 30 cm to 70 cm by the end of this century. This could result in flooding of low-lying coastal areas, including some of the world’s largest cities.
Scientists led by John Moore from Beijing Normal University, China, write that to combat global warming people need to concentrate on sharply curbing greenhouse gas emissions and not rely too much on proposed geo-engineering methods.
Geo-engineering has been talked about to counter some of the effects of climate change for the past several years, with some figures like the billionaire Bill Gates ploughing millions of dollars into research.
But there are opponents of geo-engineering techniques who argue that almost all technologies for geo-engineering our way out of climate change fail a key test: they can’t stop the sea from rising and swamping low-lying countries.
“You can’t slap the brakes on sea levels now,” says Moore. “There’s too much inertia in the system.” Moore and his colleagues modelled the effects of deploying five different geo-engineering techniques during the 21st century and combined each one with three scenarios for greenhouse gas emissions: continuing to grow at current rates, cutting back dramatically, and cutting back only slightly.
Injecting sulphate aerosols into the stratosphere -- which reduces the amount of sunlight reaching the surface of the earth -- had little effect. If emissions are allowed to grow at current rates, the model showed sea levels rising by 1.1 metres by 2100. Aerosols could reduce that to 0.8 metres by 2100, but with the rate of rise showing no sign of slowing down at the end of the century, this would simply delay greater rises, not prevent them.
Blocking sunlight with space mirrors did make sea levels start to drop by the end of the century, but only when coupled with stringent emissions cuts. The results were marginally better for a world in which biofuels were rapidly developed and the resulting carbon dioxide was locked underground. This also reversed the rise in sea level by 2100, assuming strict emissions cuts elsewhere -- though even in this scenario, the oceans still rose by 30 cm.
“Substituting geo-engineering for greenhouse emissions control would be to burden future generations with enormous risk,” said Svetlana Jevrejeva of the UK’s National Oceanography Centre, a co-author of the study.
Tim Lenton of the University of East Anglia, UK, says the study underlines the fact that what matters most is how much CO2 is in the atmosphere. As a result, he says, the priority should be to reduce emissions and create carbon sinks.
Source: BBC, August 24, 2010
http://www.newscientist.com, August 2010
http://www.nature.com, August 2010