Temperatures are on course to rise at least 4 degrees by the end of the century, according to research that finds earlier climate models projecting smaller increases are likely to be wrong.

The research, by a team led by the University of NSW, says a 4-degree rise in temperature would be potentially catastrophic for agriculture in warm regions of the world, including Australia.

New research suggests temperatures will rise between 3-5 degrees for a doubling of C02. Credit:Michael Clayton-Jones

Forecasts in many climate models for lower temperature rises were based on assumptions that clouds might help limit temperature increases.

But the team claims to have found the key to predicting cloud behaviour, and forecasts that clouds will not be nearly as helpful as thought in many models.