The climate may be less sensitive to carbon dioxide than we thought – and temperature rises this century could be smaller than expected. That's the surprise result of a new analysis of the last ice age. However, the finding comes from considering just one climate model, and unless it can be replicated using other models, researchers are dubious that it is genuine.
As more greenhouse gases enter the atmosphere, more heat is trapped and temperatures go up – but by how much? The best estimates say that if the amount of carbon dioxide in the atmosphere doubles, temperatures will rise by 3 °C. This is the "climate sensitivity".
But the 3 °C figure is only an estimate. In 2007, the Intergovernmental Panel on Climate Change (IPCC) said the climate sensitivity could be anywhere between 2 and 4.5 °C. That means the temperature rise from a given release of carbon dioxide is still uncertain.
To pin down the sensitivity, Andreas Schmittner of Oregon State University, Corvallis, and colleagues took a close look at the Last Glacial Maximum around 20,000 years ago, when the last ice age was at its height.
Read the whole thingCO2 may not warm the planet as much as thought - environment - 24 November 2011 - New Scientist
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