CO2 may not warm the planet as much as thought

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".