The IPCC report is the third of four this year in a review that will guide government policymakers. The IPCC draws on the work of 2,500 scientists from more than 130 countries and last issued reports in 2001.

EMISSIONS

"Global greenhouse gas emissions have grown since pre-industrial times, with an increase of 70 percent between 1970 and 2004," it says. Emissions are set to grow by between 25 and 90 percent between 2000 and 2030.

Developed countries accounted for 46 percent of all emissions in 2000 but just a fifth of the world population. Up to about 75 percent of the projected growth in emissions of carbon dioxide, the main greenhouse gas, from energy use will come from developing nations.

POTENTIAL

"There is substantial economic potential for the mitigation of global greenhouse gas emissions over the coming decades, that could offset the projected growth of global emissions or reduce emissions below current levels," it says.

Potential savings of greenhouse gases by major sectors in 2030, assuming a penalty for emitting carbon dioxide of less than $100 a tonne (world 2004 emissions were 49 billion tonnes):

COSTS

Costs of cutting greenhouse gases range between less than 3 percent of world gross domestic product in 2030, with the stiffest curbs, to a small 0.2 percent boost to growth with an easier goal.

The economic impact is spread over many years. The strictest goal, limiting concentrations of greenhouse gases to 445 parts per million of the atmosphere, would brake annual GDP growth rates by less than 0.12 percent a year.