The relationship between the measure of climate forcing and the magnitude of the climate change; see Tomassini et al. (2007) J. Climate 20, 7 and Cash (2007) Tellus A 59, 2 on the origin of climate sensitivity differences, defined by Denby et al. (2002) Tellus A 54, 5 as the change in climate brought about by increasing radiative forcing (radiation). See Voigt et al. (2007) Glob. Change Biol. 13, 8 on trophic climate sensitivity.