John Vidal theguardian.com, Tuesday 25 February 2014 11.41 EST
Geoengineering the planet’s climate: even when applied on a massive scale, the most that could be expected is a temperature drop of about 8%, new research shows. Photograph: Nasa/REUTERS
Large-scale human engineering of the Earth’s climate to prevent catastrophic global warming would not only be ineffective but would have severe unintended side effects and could not be safely stopped, a comparison of five proposed methods has concluded.
Science academies around the world as well as some climate activists have called for more research into geoengineering techniques, such as reflecting sunlight from space, adding vast quantities of lime or iron filings to the oceans, pumping deep cold nutrient-rich waters to the surface of oceans and irrigating vast areas of the north African and Australian deserts to grow millions of trees. Each method has been shown to potentially reduce temperature on a planetary scale.
But researchers at the Helmholtz Centre for Ocean Research Kiel, Germany, modelled these five potential methods and concluded that geoengineering could add chaos to complex and not fully understood weather systems. Even when applied on a massive scale, the most that could be expected, they say, is a temperature drop of about 8%.
The potential side effects would be potentially disastrous, say the scientists, writing in Nature Communications. Ocean upwelling, or the bringing up of deep cold waters, would cool surface water temperatures and reduce sea ice melting, but would unbalance the global heat budget, while adding iron filings or lime would affect the oxygen levels in the oceans. Reflecting the sun’s rays into space would alter rainfall patterns and reforesting the deserts could change wind patterns and could even reduce tree growth in other regions.
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