"If politicians from G8 countries want to take this seriously, they have the chance to act responsibly on this report," Muller said of the third report by the UN Intergovernmental Panel on Climate Change (IPCC) due on Friday.

Germany has set a target to reduce emissions by 40 percent by 2020 and 80 percent by 2050, Muller said, adding that it was achievable through renewable energy and new technologies.

"That is the German goal and we think it is possible in all industrialised nations," he said. Scientists and government officials from more than 100 countries meeting since Monday have yet to reach agreement on the costs of curbing emission of greenhouse gases and stabilising levels of the gases in the atmosphere.

The European Union, which has already set a target of cutting greenhouse gas emissions by at least 20 percent by 2020, says curbing emissions will not cost that much.

But China objects to any language that suggests a cap on emissions or stabilisation levels that could leave it vulnerable to demands in future climate talks to slow its rapid economic growth or spend vast sums on cleaner technology.

"It is very difficult to anchor this target at the conference," Muller said, referring to a bid to stabilise emissions at slightly above current levels.

"The delegation from China tries massively to prevent such a position and there are not a few states that hide behind them," he said.

The previous two IPCC reports painted a grim future, with global warming causing more hunger, droughts, heatwaves and rising seas. The first report in February said it was at least 90 percent certain mankind was to blame for warming to date.

Olav Hohmeyer, a German environmental economics professor and one of the authors of the latest IPCC report, said the rift was not only between Europe and China, which along with India relies heavily on coal to feed its fast-growing economy.

The United States is also reluctant to curb its appetite for fossil fuels, while oil producer Saudi Arabia and coal suppliers South Africa and Australia oppose any moves that would limit their energy sales.

"These positions are almost cast in stone and the negotiations are always about how far our friends can go," he said.

Nevertheless, Hohmeyer expected the final report to be a "fair compromise" that would offer solutions that should be acted upon now before it is too late.

"Without the necessary policy framework and the high commitment of all governments in the world to mitigation, we will lose too much time.