Clearing the air

Emissions trading

The Kyoto Protocol on Climate Change has suffered some significant setbacks since it was first agreed seven years ago. The US, the world's largest producer of carbon dioxide, has steadfastly refused to ratify the treaty, which aims to curb the emission of greenhouse gases blamed for global warming. More than 140 countries have ratified the accord, but without the buy-in of the US, these account for just 55% of greenhouse gas emissions.

But there have been successes too, among them the start of