"Copenhagen climate change talks are last chance", Gordon Brown

There are now fewer than 50 days to set course of next 50 years and more, PM tells environment ministers from 17 countries responsible for 80% of greenhouse gas emissions.

Gordon Brown today warned that the world is on the brink of a "catastrophic" future of killer heatwaves, floods and droughts unless governments speed up negotiations on climate change before vital talks in Copenhagen in December. This applies to the US as much as anyone, he said, adding that "there is no plan B", and that agreement cannot be deferred beyond the UN-sponsored Copenhagen conference.

There are fears that Barack Obama does not have the political capital to reach a deal in Copenhagen and will instead use a visit to China next month to reach a bilateral deal that circumvents the UN. Downing Street is also concerned that there is no agreement on how to finance a climate change package in developing countries.

The prime minister delivered his warning to a meeting of environment ministers brought together under the umbrella of the Major Economies Forum. The 17 countries in the forum are responsible for 80% of greenhouse gas emissions. Brown told them: "In every era there are only one or two moments when nations come together and reach agreements that make history, because they change the course of history. Copenhagen must be such a time. There are now fewer than 50 days to set the course of the next 50 years and more.

"If we do not reach a deal at this time, let us be in no doubt: once the damage from unchecked emissions growth is done, no retrospective global agreement in some future period can undo that choice. By then it will be irretrievably too late."

Brown said that, according to estimates from the intergovernmental panel on climate change, an extra 1.8bn people – a quarter of the world's population – could be short of water by 2080 as a result of climate change. And the threat was not confined to people in the developing world, Brown said.

"The extraordinary summer heatwave of 2003 in Europe resulted in over 35,000 extra deaths. On current trends, such an event could become quite routine in Britain in just a few decades' time," he said.

"And within the lifetime of our children and grandchildren the intense temperatures of 2003 could become the average temperature experienced throughout much of Europe. In Britain we face the prospect of more frequent droughts and a rising wave of floods."

Brown said that he thought a deal at Copenhagen was possible. But negotiators were "not getting to agreement quickly enough", Brown went on, which was why he was appealing for leaders to get involved personally. "We cannot compromise with the earth, we cannot compromise with the catastrophe of unchecked climate change, so we must compromise with one another," he said.

"I urge my fellow leaders to work together to reach agreement amongst us, recognising both our common and our differentiated responsibilities – and the dire consequences of failure."

Ed Miliband, the climate change secretary, yesterday highlighted signs of movement, pointing out that last month India said it was ready to set itself non-binding targets for cutting carbon emissions, while China said it would curb the growth of its emissions by a "notable margin" by 2020, although it did not specify further.

The US special envoy for climate change, Todd Stern, said developing economies must boost their efforts to curb emissions, warning it was "certainly possible" that no deal would be agreed in Copenhagen. "What we need to have happen is for China and India and Brazil and South Africa and others to be willing to take what they're doing, boost it up some, and then be willing to put it into an international agreement," he said.