Gas emissions 'largely down to the rich'

A study published in the latest edition of the journal found that in 2004 each US citizen accounted for more than two tons of consumer-generated carbon dioxide that was produced somewhere else.

For Europeans, the figure was thought to exceed 3.6 tons per person.

The scientists used published trade data from 2004 to model the flow of products across 57 industry sectors and 113 countries or regions.

By allocating carbon emissions to particular products and sources, they were able to calculate the net emissions "imported" or "exported" by different countries.

Co-author Ken Caldeira explained that instead of looking at carbon dioxide emissions "only in terms of what is released inside our borders, we also looked at the amount of carbon dioxide released during the production of the things that we consume."

Researchers found that most of the "outsourcing" was to developing countries, especially China.

China recently replaced the US as the most highly emitting country.

But 22.5 per cent of China's emissions derive from the production of goods and services destined to be consumed overseas.

Study leader Dr Steven Davis said: "To the extent that constraints on developing countries' emissions are the major impediment to effective international climate policy, allocating responsibility for some portion of these emissions to final consumers elsewhere may represent an opportunity for compromise."