CLIMATE change adviser Ross Garnaut has lambasted Australian executives for destroying shareholder funds in the blind belief China's demand for Australia's big three mining exports would continue to climb.

While they had splurged on ''wasteful over-investment'', China had been making good on its promise to cut its emissions intensity and had been sourcing iron ore from elsewhere.

''It happens that the Chinese structural change has had its most severe effect precisely on the three commodities which have been at the centre of the Australian resources boom - iron ore, metallurgical coal and thermal coal,'' he told a Melbourne Institute conference. ''The awful reality is that parts of corporate Australia have dissipated shareholders's funds by underestimating the seriousness of Chinese commitments to reduce the emissions intensity of economic growth.''

Speaking at the same conference, the Treasurer, Wayne Swan, warned of a ''savage blow'' to the global recovery unless Republicans and Democrats in the US could agree on a way to prevent a crisis in December when large numbers of tax cuts will automatically expire.

Professor Garnaut said China had exceeded its ambitious emissions targets, cutting coal-fired generation by more than 7 per cent in the past year. A rapid expansion in hydroelectricity, and wind, biomass, solar and nuclear power, had pushed down coal's share of energy production from 85 to 73 per cent.

Australia's iron ore exporters would soon have to compete with massive new Chinese-funded mines in West Africa created in part by Australia's decision to block Chinese investment at home.

The forecasts for iron ore and coal exports in the government's Asian Century white paper were barely believable, their credibility protected only by the presence of ''low'' projections along with so-called medium and high projections.

Gas and uranium would be far more important to Australia's prosperity than the ''diminished prospects for the staples of the early 21st century''.

Mr Swan built on his September attack on the ''cranks and crazies'' he said had taken over parts of the Republican Party, saying the ''looming fiscal cliff'' in the US could plunge it back into recession.

The legislated unwinding of a decade's worth of tax cuts and spending programs on December 31 would, ''left unattended, see the the US economy suffer a crushing annualised contraction of 2.9 per cent in the first half of next year''.

''Whoever wins the presidential election in less than a week's time and whoever controls the Congress will have choices to urgently make,'' Mr Swan said.

He will fly to Mexico for the G20 finance ministers meeting at the weekend and then to Washington for meetings with the head of the International Monetary Fund, Christine Lagarde, and the head of the US Federal Reserve, Ben Bernanke.

Professor Garnaut said had been blessed to have a mining boom following the largest consumption and housing boom on record. The challenge was to ''come down from our hump in incomes and expenditure without precipitating recession''.