Earth sunshade would not rewind the climate
-   +   A-   A+     03/06/2008

Father of the mobile phone: Marty Cooper: Cooper filed a patent for the radio telephone system in 1973, while working at Motorola, and was the first person to make a call on a portable mobile phone. (He called a rival engineer at Bell Labs.) Cooper has stated that his inspiration came from watching Star Trek Captain Kirk talk on his communicator device. Today, Cooper is the CEO and founder of ArrayComm.

ANYONE clinging to the notion that we can wipe the slate clean of all our climate mistakes by deflecting the sun is rays with space mirrors is in for a disappointment.

Dan Lunt of the University of Bristol, UK, and colleagues carried out the most detailed climate-modelling study to date on the impact of a sunshade. They simulated Earth is climate under three scenarios: pre-industrial times; a future climate with atmospheric carbon dioxide at an extreme level of four times pre-industrial values; and a sunshaded geo-engineered climate with the same high CO2 levels but solar radiation reduced by 4 per cent - similar to Cambrian times, 500 million years ago.

They found that Earth under a sunshade would not simply revert to its pre-industrial climate. Instead the tropics would be cooler than pre-industrial times by 1.5 °C, while high latitudes would be warmer by 1.5 °C, leading to less sea ice - bad news for animals that fish from the ice. Average precipitation would also drop by 5 per cent, according to the model. The work will appear in Geophysical Research Letters.

The findings could be the final straw, as there are other drawbacks to building a sunshade. "It would be expensive, disastrous if the mirrors ever failed and leaves other issues un-addressed such as ocean acidification," Lunt says.

Climate Change – Want to know more about global warming: the science, impacts and political debate? Visit our continually updated special report.

From issue 2658 of New Scientist magazine, 28 May 2008, page 19


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