ANYONE clinging to the notion that we can wipe the slate clean of all our climate mistakes by deflecting the sun鈥檚 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鈥檚 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 鈥� 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 掳C, while high latitudes would be warmer by 1.5 掳C, leading to less sea ice 鈥� 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.
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The findings could be the final straw, as there are other drawbacks to building a sunshade. 鈥淚t would be expensive, disastrous if the mirrors ever failed and leaves other issues un-addressed such as ocean acidification,鈥� Lunt says.
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