Paris/London - Nothing less than "a low-carbon energy revolution" is necessary to reduce greenhouse gas emissions and limit global warming to acceptable levels, the International Energy Agency (IEA) said Tuesday.

A consensus is growing on the need to limit the rise in global temperatures to 2 degrees Celsius, and for that to occur the concentration of greenhouse gases in the atmosphere needs to be stabilized at around 450 parts per million of carbon dioxide.

"This objective can be achieved... through radical and co-ordinated policy action across all regions," the IEA said in its World Energy Outlook, launched Tuesday in London.

However, if governments take no action on global warming and energy use, the result would be "rapidly increasing dependence on fossil fuels, with alarming consequences for climate change," the IEA warned.

Under this pessimistic scenario, energy-related carbon dioxide emissions are projected to increase from 28.8 gigatons (Gt) in 2007 to 34.5 Gt in 2020 and 40.2 Gt in 2030, an average rate of growth of 1.5 per cent per year.

Most of that 11.4 Gt increase over 33 years would come from China (6 Gt), India (2 Gt) and the Middle East (1 Gt), while emissions in the industrialized nations of the Organization for Economic Cooperation and Development (OECD) are projected to fall slightly, the IEA said.

This scenario would result in average global temperatures rising by up to 6 degrees Celsius, which "would lead almost certainly to massive climatic change and irreparable damage to the planet," the IEA warned.

In the alternative scenario, "which depicts a world in which collective policy action is taken to limit the concentration of greenhouse gases in the atmosphere," energy demand grows by only 20 per cent between 2007 and 2030, an average annual growth rate of 0.8 per cent.

In addition, the use of fossil fuels, such as coal and oil, is increasingly replaced by low- or zero-carbon sources, such as nuclear power and renewables, with the share of non-fossil fuels increasing from 19 per cent in 2007 to 32 per cent in 2030.

"Increased energy efficiency in buildings and industry reduces the demand for electricity ... The average emissions intensity of new cars is reduced by more than half, cutting oil needs," the IEA said.

As a result, global energy-related carbon dioxide emissions would peak at 30.9 Gt before 2020, and then actually decline to 26.4 Gt in 2030, 2.4 Gt lower than 2007 levels and 13.8 Gt less than the scenario in which governments simply sat on their hands.

"The time to act has arrived," the IEA said, and urged the leaders who will be meeting in Copenhagen in December for a UN climate change meeting "to negotiate a successor treaty to the Kyoto Protocol - one that puts the world onto a truly sustainable energy path."

The agency added that the speed with which governments act on their climate change commitments will be critical. "Saving the planet cannot wait," the IEA said. (dpa)