claim: Some global warming 'skeptics' argue that the Earth's climate sensitivity is so low that a doubling of atmospheric CO2 will result in a surface temperature change on the order of 1°C or less, and that therefore global warming is nothing to worry about.
evidence: The 1990 IPCC First Assessment Report estimated that equilibrium climate sensitivity to a doubling of CO 2 lay between 1.5 and 4.5 °C ( 2.7 and 8.1 °F ), with a best guess in the light of current knowledge of 2.5 °C ( 4.5 °F ).