Rapidly escalating levels of atmospheric carbon dioxide may produce a slower rate of global warming than some scientists have feared, according to a new study in the prestigious journal Science.

The authors of the study stressed that man-made global warming was real and warned that increase in atmospheric carbon dioxide was likely to cause serious damage.

But, analysing paleoclimate data, they found the rate of warming was likely to be at the lower end of the projections of the United Nations' Intergovernmental Panel on Climate Change (IPCC).

The IPCC found there was a 66 per cent probability that doubling the carbon dioxide in the atmosphere would lead to a temperature rise of between 2 and 4.5 degrees.

The new study funded by the US National Science Foundation estimated the warming at this level of emissions was most likely to be 2.3 degrees, with a 66 per cent probability it would be between 1.7 and 2.6 degrees.