Beliefs, evidence, and climate action
by Mark Freeman, Ben Groom, Frikk Nesje, and Gernot Wagner
Abstract:
We assess how changes in the scientific consensus around equilibrium climate sensitivity (ECS), as captured by the IPCC’s Fifth (AR5) and Sixth (AR6) Assessment Reports, impact policymakers’ willingness to take climate action. Taking the IPCC’s reports at face value, the ECS estimates in AR6 would have lowered a policymaker’s willingness to act on climate relative to AR5 due to a narrower "likely" range. However, Bayesian updating may reverse this conclusion. An accuracy-motivated policymaker who was not convinced to take greater climate action by the evidence in AR5 may be more likely to increase their investment in clean energy by the evidence in AR6.
Keywords: Climate policy, Energy policy, Climate risk, Equilibrium climate sensitivity, Bayesian updating
JEL: D83, H51, Q48, Q54
Full paper: "Beliefs, evidence, and climate action" (13 May 2026); CESifo Working Paper No. 11668, forthcoming in Energy Economics (as of 17 May 2026).
Presented at: EARE Conference 16-19 June 2025, Bergen, Norway [by co-author Frikk Nesje]; Knightian Uncertainty Workshop on Climate Finance, Columbia (10 March 2026).
