Sydney - Australia would be foolish to act alone on global warming, the government's top climate change adviser said Wednesday.

Economist Ross Garnaut, who has recommended Canberra set itself a 10-per-cent reduction target for 2020, said those pushing for more ambitious targets would be mugged by reality at next year's climate change conference in Copenhagen.

"The very worst outcome would be a lot of high sounding principles being agreed upon at the end of next year at Copenhagen but there being no substance behind them," he said. "The world can't afford to have that happen again. It happened, more or less, at Kyoto."

He warned Prime Minister Kevin Rudd that it would be economic suicide for Australia to adopt ambitious targets that were not shared by other big carbon emitters.

Australia is among the world's biggest per capita emitters.

"Let's face the reality - the only solution will be a global solution," Garnaut told national broadcaster ABC.

"Australia could cut emissions to zero, could do it tomorrow - it couldn't actually do it, but if it did do it - it would have almost no effect on global warming."

Garnaut said the best outcome at the UN conference in Copenhagen was agreement on cutting carbon emissions by 25 per cent by 2020, and by 90 per cent by 2050.

"If we had an international agreement that was actually working around a reasonably ambitious outcome but not the ideal one, then you would build confidence that the world could actually deal with that problem without bringing prosperity to an end," he said. (dpa)