Mr de Boer suggested that a deal in Copenhagen would involve rich countries accepting big cuts and helping poor ones to curb the growth of their emissions with handouts of cash and technology. Agreeing on exact numbers, however, will be difficult. Many climate pundits assume the meat of a deal will be reached in other, smaller groupings. Mr Obama plans to reconvene Mr Bush’s much-reviled club of countries responsible for most of the world’s emissions, now renamed the Major Economies Forum. He has also sent Mr Stern and Hillary Clinton, his secretary of state, to talk to China about climate.

The slowness of negotiations is stirring anxiety in some quarters. As green activists moaned, the G20 summit in London risked neglecting climate at the expense of economics. But not entirely: Prince Charles, heir to the British throne, used the moment to call in senior types from Brazil, Indonesia and America, among other places, to discuss short-term efforts to protect tropical forests before a UN-backed plan kicks in. With the leaders of Japan, France, Germany and Italy in attendance, it may have been the highest-level talk about trees ever held. Participants listened with approval to their host’s idea that new ways be found for rich states, and investors, to send cash-swiftly but conditionally-to poor, forested countries.

As the UN talks inched on, news came that an “ice bridge” yoking the Wilkins ice shelf to the Antarctic Peninsula had snapped. That may set adrift an iceberg as big as Jamaica, and speed the flow of hitherto pent-up glaciers into the sea. Whether it will energise diplomats is less clear.

... contd.