From the BBC:

German Chancellor Angela Merkel, hosting the summit, has set what is seen as an ambitious personal goal of persuading the leading industrialised countries to commit to cutting emissions by 50% by 2050.

She also wants them to increase fuel efficiency by 20% and limit the world's temperature rise to 2C.

However, President George W Bush's senior climate adviser said on Wednesday that a number of countries - including the US - would not sign up to those commitments.

James Connaughton insisted that there had been significant progress and consensus on the issue of climate change. But he made clear the US did not believe the G8 should be the forum for setting targets.

"There is significant agreement that those should be established on a national basis, and the only area of disagreement is that the G8 should dictate the national policies of its members," he said.