Magazine article Geographical

Can Space Mirrors Save the Planet? as It Becomes Ever Clearer That Simply Cutting Back on Carbon Emissions Isn't Going to Save the Poles, a Growing Number of Scientists Are Looking to Increasingly Ambitious Technological Fixes to Halt the Tide of Global Warming

Magazine article Geographical

Can Space Mirrors Save the Planet? as It Becomes Ever Clearer That Simply Cutting Back on Carbon Emissions Isn't Going to Save the Poles, a Growing Number of Scientists Are Looking to Increasingly Ambitious Technological Fixes to Halt the Tide of Global Warming

Article excerpt

Listen to the rhetoric surrounding global climate change and you tend to hear words such as 'mitigation' and phrases such as 'limiting the temperature rises'. What you won't hear is talk of 'solutions' or 'cures'. Such is our dependence on fossil fuels, and such is the volume of carbon dioxide that we have already released into the atmosphere, that climate scientists all agree that significant global warming is now inevitable--the best we can hope to do is keep it at a reasonable level, and even that is going to be an uphill task.

At present, the only serious option on the table for doing this is cutting back on our carbon emissions, but while a few countries are making major strides in this regard, the majority are having great difficulty even stemming the rate of increase, let alone reversing it.

Consequently, an increasing number of scientists are beginning to explore the alternatives. And they're thinking big. From placing giant sunshades in space to pumping sulphates into the atmosphere at high altitudes, the schemes appear limited only by the imagination of the scientists themselves. They all fall under the banner of geoengineering--generally defined as the intentional large-scale manipulation of the environment. According to its proponents, it's the equivalent of a backup generator: if Plan A--weaning the world off its carbon addiction--fails, we require a Plan B, employing grand schemes to slow down or reverse the process of global warming.

Geoengineering has been shown to work, at least on a small, localised scale. For decades, May Day parades in Moscow have taken place under clear blue skies, aircraft having deposited dry ice, silver iodide and cement powder to disperse clouds.

Many of the schemes now suggested look to do the opposite, and reduce the amount of sunlight reaching the planet. The most eye-catching idea of all, suggested by Professor Roger Angel, an astronomer at the University of Arizona, is a proposal to erect a space parasol system. The scheme which in 2006 secured a research grant from NASA--would employ up to 16 trillion minute spacecraft, each weighing about one gram, to form a transparent, sunlight-refracting shade in an orbit 1.S million kilometres above the Earth. The spacecraft would be launched in groups every five minutes for ten years, and could, argues Angel, reduce the amount of light reaching the Earth by two per cent.

The majority of geoengineering projects--which include planting forests in deserts, depositing iron in the ocean to stimulate the growth of algae, or using sea-salt particles to halt rainfall and extend cloud cover--have focused on achieving a general cooling of the Earth. But some look specifically at reversing the melting at the poles, particularly the Arctic, and even more particularly, the Greenland ice sheet. The reasoning is that if you replenish the ice sheets and frozen waters of the high latitudes, more light will be reflected back into space, applying a handbrake to the warming of the oceans and atmosphere.

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The concept of releasing aerosol sprays into the stratosphere above the Arctic has been proposed by several scientists. This would involve using sulphur or hydrogen sulphide aerosols to create clouds of sulphur dioxide, which would, in turn, lead to a global dimming. The idea is modelled on historic volcanic explosions, such as that of Mount Pinatubo in the Philippines in 1991, which led to a short-term cooling of global temperatures by 0.5[degrees]C. The scheme has been given some credence by Dr Paul Crutzen, winner of the 1995 Nobel Prize for chemistry for his work on the ozone layer, who argued in 2006 that the aerosols could be delivered by artillery, high-flying aircraft or balloons.

Other techniques have suggested bolstering the ice cap by spraying it with water. Using pumps to carry water from below the sea ice, the spray would come out as snow or ice particles, producing thicker sea ice with a higher albedo (the ratio of sunlight reflected from a surface) to reflect summer radiation. …

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