Some world leaders at the Copenhagen talks on climate change declared on Friday night that they had reached a “meaningful agreement” but admitted it fell well short of their ambitions for the first truly global treaty on cutting greenhouse gases.

Barack Obama, the US president, said further talks were needed to secure a formal treaty to replace the 1997 Kyoto accord. “What we have achieved in Copenhagen will not be the end but the beginning of a new era of international action,” he said. “This is going to be hard. It's hard within countries, and it's going to be even harder between countries”

Sergio Serra, Brazil's ambassador for climate change issues, described the result of the talks as ”disppointing”. He added: ”There is a big job ahead to avoid climate change through emissions reduction targets, and that was not done here.”