The 1990 IPCC First Assessment Report estimated that equilibrium climate sensitivity to doubling lay between 1.5 and 4.5 °C, with a "best guess in the light of current knowledge" of 2.5 °C [REF].
The TAR uses the word "likely" in a qualitative sense to describe the likelihood of the 1.5 to 4.5 °C range being correct [REF].