Boosting energy-efficiency and the use of renewables not only helps secure energy supplies and cuts local pollution, but also helps keep carbon emissions in check too.

ECONOMIST: China, India and climate change

Heavy pollution cuts into the usable water supply, but treatment equipment is expensive.

ECONOMIST: China

But US emissions cuts look much more impressive if you count cuts in agricultural pollution, the contributions to preserving forests in developing nations and buying emissions allowances from poor countries.

BBC: Climate chief's pledge on energy

The World Resources Institute estimate that if all the credits were translated into genuine pollution cuts it would lead to the equivalent of perhaps 23% American reductions on 1990 levels, which is very much in line with Europe's 20% offer.

BBC: Climate chief's pledge on energy

Since Mr Bush took office, the number of days when Texan cities have exceeded federal ozone standards has doubled, and Houston and Dallas currently face federal deadlines to make sharp cuts in air pollution or risk losing federal money for their roads.

ECONOMIST: The Lone Smog State | The