claim: Fourth Assessment Report ( AR4 ), in which the likely range is given as 2.0°C to 4.5°C, with a best estimate of 3.0°C ( Pat Michaels )
evidence: Surface air warming in the 21st century : Best estimate for a low scenario is 1.8 °C with a likely range of 1.1 to 2.9 °C ( 3.2 °F with a likely range of 2.0 to 5.2 °F ) Best estimate for a high scenario is 4.0 °C with a likely range of 2.4 to 6.4 °C ( 7.2 °F with a likely range of 4.3 to 11.5 °F ) A temperature rise of about 0.1 °C per decade would be expected for the next two decades, even if greenhouse gas and aerosol concentrations were kept at year 2000 levels.