From The Guardian UK
By George Monbiot

Challenging a Nobel laureate over a matter of science is not something you do lightly. I have hesitated and backed off, read and reread his paper, but now I believe I can state with confidence that Paul Crutzen, winner of the 1995 prize for chemistry, has overlooked a critical scientific issue.

Crutzen is, as you would expect, a brilliant man. He was one of the atmospheric chemists who worked out how high-level ozone is formed and destroyed. He knows more than almost anyone about the impacts of pollutants in the atmosphere. This is what makes his omission so odd.

This month, he published an essay in the journal Climatic Change. He argues that the world’s response to climate change has so far been “grossly disappointing”. Stabilising carbon dioxide concentrations in the atmosphere, he asserts, requires a global reduction in emissions of between 60% and 80%. But at the moment “this looks like a pious wish”. So, he proposes, we must start considering the alternatives, by which he means re-engineering the atmosphere in order to cool the earth.

He suggests we use either giant guns or balloons to inject sulphur into the stratosphere, 10km or more above the surface of the earth. Sulphur dioxide at that height turns into tiny particles – or aerosols – of sulphate. These reflect sunlight back into space, counteracting the warming caused by manmade climate change.

One of the crueller paradoxes of climate change is that it is being accelerated by reducing certain kinds of pollution. Filthy factories cause acid rain and ill health, but they also help to shield us from the sun, by filling the air with particles. As we have started to clean some of them up, we have exposed ourselves to more solar radiation. One model suggests that a complete removal of these pollutants from the atmosphere could increase the world’s temperature by 0.8C.

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