Reengineering Earth to stop climate change

The Economist has a great feature on geo-engineering, approaches to tweak the environment on a planetary scale to help stop human-induced climate change. The article is a survey of the Royal Society's special journal edition on "Geoscale engineering to avert dangerous climate change." Some of the proposed approaches to scrub carbon dioxide from the atmosphere or block some of the sunlight hitting Earth sound straight out of the pages of science fiction. Extreme times might call for extreme tech though. From The Economist:

Reflecting sunlight back into outer space (increasing the Earth's albedo, as it is known) would also cool the planet, and the Royal Society's authors consider two ways of doing so.

One, which has been widely touted in the past is, perversely, to increase the amount of pollution in the atmosphere. Governments have spent the past half-century trying to reduce the amount of sulphur compounds in the air. These compounds are the main cause of acid rain. They also, however, have a tendency to form tiny particles that reflect sunlight back into space. That effect is most noticeable when a volcano erupts explosively, as Mount Pinatubo did in 1991, or Tambora did in 1815. Those eruptions put sulphate particles into the stratosphere, and because that is above the part of the atmosphere where weather occurs, these particles tended to stay there rather than being washed out by rain. That cooled the whole climate. The year after Tambora's explosion was known for a long time as the "year without a summer".

The reverse is also true. When civilian flights over the United States stopped in the wake of the terrorist attacks of September 2001, the lack of sulphur-laden contrails led to a perceptible rise in temperature. Philip Rasch, of the National Centre for Atmospheric Research, in Boulder, Colorado, and his colleagues are therefore exploring the idea of deliberately polluting the stratosphere with sulphate in order to reflect solar heat back into space….

Besides polluting the stratosphere, there is another way of changing the atmosphere to make it more reflective. This is to tinker with cloud cover. One person working on this idea is Stephen Salter, a marine engineer at the University of Edinburgh best known for seeking to replace fossil fuels with Salter's duck, a device for turning ocean waves into electricity.

"A Changing Climate of Opinion?" (The Economist, thanks Timo Hannay!)