Campaigners have responded with caution after steps were taken to halt climate change on Thursday at the G8 summit in Heilegendamm, Germany.

The final communiqué followed 24 hours of negotiations and months of behind-the-scenes bargaining.

The G8 leaders committed themselves to making 'substantial cuts' in CO2 emissions. They said that a framework for this would be worked out through the UN by 2009. This means that the US administration cannot pursue its own separate set of meetings as it had posited last week.

EU leaders, with Japan and Canada, also backed global cuts in carbon emissions of at least 50 per cent by 2050.

The Prime Minister Tony Blair said that he was 'surprised and pleased' at the progress made. 'The possibility is here that for the first time, we are getting a global deal on climate change with a substantial cut in emissions. The situation is transformed from two years ago'.

Finalising a long-term deal would need to involve both America and China he said. But there was a 'commitment to substantial cuts' and reducing global emissions by half by 2050.

Andy Atkins, Advocacy Director for Tearfund said the G8's communiqué represented "a significant achievement". He said, "They have jumped a couple of really important hurdles, but there are many, many more to jump. The good news is that Japan and Canada have joined the EU. Rather than fudging the issue, they have been clear about who's on board and who isn't.

"America has been pushed a bit further than they wanted to be. We are disappointed that they have not agreed altogether as the G8 to keep climate change beneath 2C, but at least some of the countries are showing what needs to be done. If globally, we could cut emissions by at least 50 per cent by 2050, that would reduce the risk of runaway climate change.'

He warned that action had to be taken to help developing countries cope with the climate change that they are already experiencing. "People are dying right now because of climate change in many developing countries," he said. "The G8 needs to take leadership on this as we are responsible for the pollution affecting developing countries now."

A spokesman for Christian Aid said, "It is disappointing that the US and Russia have not signed up to global cuts in emissions of at least 50 per cent by 2050, but important that Canada and Japan as well as the European G8 countries have."

But Bono condemned G8's leaders for "breaking their promises" to the poor. They had made a "really dumb mistake" he said in not making even further commitments on climate change.