Comment & Debate
“Earth sunshade would not rewind the climate”. New Scientist. 28 May 2008 – ANYONE clinging to the notion that we can wipe the slate clean of all our climate mistakes by deflecting the sun’s 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’s 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.
Sharon Begley. “The ‘Geo-Engineering’ Scenario”. Newsweek. Nov 23, 2007 – Cooling would be uneven [as a result of solar shielding], with some regions benefiting more than others. (What would Russia, which might benefit from global warming, do if India, which would suffer, decided to cool things down through geo-engineering?)