A year ago in Heiligendamm, Group of Eight -leaders agreed to "consider seriously . . . at least a halving of global emissions by 2050". This time they have promised to "consider and adopt a goal of achieving at least 50 per cent reduction of global emissions" by the same date.

In the rarefied world of diplomacy this counts as -significant progress. Gordon Brown, the UK prime minister, went so far as to hail it as a breakthrough.