GREENHOUSE gas emissions are escalating so rapidly they will double between 2005 and 2030 if nothing is done to stem their growth.
Government climate adviser Ross Garnaut's latest update to his 2008 review found the economic shift towards developing countries was so great they would be responsible for 70 per cent of global emissions by 2030, up from about half today.
The expansion of China and India was more than offsetting the dip in emissions growth in North America and Europe due to the financial crisis.
Australia was in a category of its own - a developed country with emissions expected to soar at an even faster rate than earlier predictions due to surging demand for fossil fuel exports. A climate change department analysis this week estimated Australia's emissions would be 24 per cent higher than 2000 levels by 2020 under current policies.
Professor Garnaut said it showed it would be hard for Australia to meet an ambitious 2020 target without a carbon price linked to international markets selling offsets, or carbon credits.
The economist said he supported the introduction of a fixed carbon tax that could later become an emissions trading scheme - a model also favoured by key members of the multi-party climate committee of Labor, Greens and independent MPs, which he advises. Professor Garnaut said a fixed tax was preferable to a market-based scheme while a carbon price did not have bipartisan support.
''The price would fluctuate with every change in the opinion polls if the opposition had promised to get rid of it,'' he said.
The latest Garnaut report came as some business leaders warned the government could face a public battle similar to that over the mining tax if new carbon legislation did not match the billions in compensation offered under Kevin Rudd's abandoned emissions trading scheme. They fear the influence of the Greens, who oppose compensation for coal power plants.
But Professor Garnaut said the cost of cutting emissions was likely to be modest unless businesses were unnecessarily protected by the government.
He opposes compensation for coal plants, but believes some is justified for trade-exposed industries.