New research has sharply narrowed the likely estimate of how much the Earth will warm with a doubling of carbon dioxide in the atmosphere, potentially honing estimates that have stood for a quarter century.
The long-standing estimate for the so-called equilibrium climate sensitivity used by the Intergovernmental Panel on Climate Change had been that surface temperatures would rise between 1.5 and 4.5 degrees for each doubling of CO2 or equivalent greenhouse gases.
The new study by UK scientists, published today in Nature journal, used year-on-year global mean temperature fluctuations rather than trends to discount the extreme ends of that range.
"Our study all but rules out very low or very high climate sensitivities, so we now know much better what we need to [do]," said Peter Cox, a professor of climate system dynamics from the University of Exeter, and the lead author of the paper.
"Climate sensitivity is high enough to demand action, but not so high that it is too late to avoid dangerous global climate change".
The researchers calculated the range to be between 2.2 and 3.4 degrees with each CO2 doubling, including a central estimate of 2.8 degrees. The IPCC's mid-range estimate was similar at 3 degrees.