Unless this trend is curbed, he says, the UK will miss its targets on curbing climate change and sulphur pollution.

BBC: Cheap coal 'threatens UK pollution targets'

However, yet another study published this year suggests it is going away as anti-sulphur pollution-control measures kick in.

ECONOMIST: Changing science

Sulphur dioxide pollution in America has been cut by a successful cap-and-trade system.

ECONOMIST: Climate change

The success of pollution taxes in Europe and of emissions-trading systems for sulphur dioxide in America show that these are a far better way of encouraging innovation than technology mandates or direct subsidies.

ECONOMIST: Energy and the environment