Failure to deal with climate change now will “haunt humanity” forever, the nation’s top greenhouse adviser has warned as he issued a rallying cry for action.

Professor Ross Garnaut has warmed to the idea of a deep, fast cut to Australia’s emissions in his final report, released on Tuesday.

After infuriating green groups earlier this month by calling for a 10 per cent cut in Australia’s emissions by 2020, he’s now more open to a deeper 25 per cent cut.

Garnaut issued a blunt assessment of the dangers of climate change as he launched the 620-page report.

“If we fail, on a balance of probabilities, the failure of our generation will haunt humanity until the end of time,” he told reporters in Canberra.

“We are entering territory here that humanity has not been in before.

“We will delude ourselves if we think that uncertainty about the climate change science … is a cause for delay.”

And Australia would probably be “the biggest loser” among developed countries from climate change, he said.

Garnaut has recommended Australia push for a strong global climate pact, which would mean a 25 per cent cut in emissions by 2020.

“Strong mitigation, with Australia playing its proportionate part, is in Australia’s interests,” the report says.

This ambitious target would be in the context of a global deal to keep atmospheric carbon concentration to 450 parts per million (ppm).

However, Garnaut is pessimistic about the possibility of the world agreeing to this “strong mitigation” deal.

If his scepticism proves correct, Garnaut wants the nation to push for a global atmospheric carbon concentration of 550 ppm, which means Australia cutting emissions by 10 per cent by 2020.

And if no climate deal is forged out of the United Nations process, Australia should cut emissions by five per cent, Garnaut says.

“There’s no point in hiding from reality,” he said about the possibility of a strong global climate pact.

He wants Australia to start emissions trading in 2010, and warned consumers would pay more.

“Consumers will wear the majority of the cost of an emissions trading scheme, paying more for a range of goods and services as businesses pass on the emissions price,” he said.

Electricity would cop the biggest price rise, rising by 37 per cent by 2020 if a deep emissions cut was made, and by 21 per cent if a more modest cut was made. Other prices would rise too, although the impact would be less than the GST had been.

“Petrol and food prices, general prices, will increase to some extent as a result of the ETS.”

Garnaut thinks half the revenue from emissions trading should go to households, 30 per cent to businesses, and 20 per cent to research. Householders would be able to access a “green credit” arrangement to install energy-smart appliances.

Garnaut said the global financial crisis, which worsened overnight, was no excuse to delay acting on climate change.

“Financial crises are short-term phenomena … climate change is a long-term structural issue.”