Post by havelock on Aug 25, 2010 19:36:27 GMT
Almost all the technologies for geoengineering 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 John Moore of Beijing Normal University in China. "There's too much inertia in the system."
Moore and colleagues modelled the effects of deploying five different geoengineering 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, or cutting 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. 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 centimetres.
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.
Journal reference: Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1008153107
from www.newscientist.com/article/dn19353-geoengineering-wont-undo-sea-levels-rises.html
"You can't slap the brakes on sea levels now," says John Moore of Beijing Normal University in China. "There's too much inertia in the system."
Moore and colleagues modelled the effects of deploying five different geoengineering 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, or cutting 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. 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 centimetres.
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.
Journal reference: Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1008153107
from www.newscientist.com/article/dn19353-geoengineering-wont-undo-sea-levels-rises.html
