Making sense of palaeoclimate sensitivity

Abstract

Many palaeoclimate studies have quantified pre-anthropogenic climate change to calculate climate sensitivity (equilibrium temperature change in response to radiative forcing change), but a lack of consistent methodologies produces a wide range of estimates and hinders comparability of results. Here we present a stricter approach, to improve intercomparison of palaeoclimate sensitivity estimates in a manner compatible with equilibrium projections for future climatechange.Over the past65millionyears, this reveals a climate sensitivity (inKW21m2) of 0.3–1.9 or 0.6–1.3 at95%or 68% probability, respectively. The latter implies a warming of 2.2–4.8K per doubling of atmospheric CO2, which agrees with IPCC estimates.