claim: Elementary radiative-transfer calculations demonstrate that a natural surface global brightening amounting to ~1.9 Wm–2 over the 18-year period of study would be expected – using the IPCC’s own methodology – to have caused a transient warming of 1 K ( 1.8 F° ).
evidence: The global temperature increase since the beginning of the industrial period ( taken as 1750 ) is about 0.8 °C ( 1.4 °F ), and the radiative forcing due to CO 2 and other long-lived greenhouse gases – mainly methane, nitrous oxide, and chlorofluorocarbons – emitted since that time is about 2.6 W / m2.