Climatic Change

, Volume 132, Issue 4, pp 519–529

Moving targets—cost-effective climate policy under scientific uncertainty


DOI: 10.1007/s10584-015-1447-6

Cite this article as:
Gerlagh, R. & Michielsen, T.O. Climatic Change (2015) 132: 519. doi:10.1007/s10584-015-1447-6


The IPCC’s fifth assessment report of Working Group III has just come out. It pays special attention to the 2 °C temperature target and tells us that the window of opportunity to prevent such climate change is rapidly closing. Yet, the report also presents a portfolio of stabilization targets, reflecting a fundamental ambiguity: there is no unique “dangerous” climate threshold. Here, we describe a framework for the evaluation of optimal climate policy given an uncertain formal climate threshold. We find that uncertainty leads to moving targets: even when the available information does not change, future regulators will tend to relax current climate plans.

We develop a reduced form integrated assessment model to assess the quantitative significance of our findings. We calibrate preferences such that in 2000 a stabilization target of 450 ppmv maintains the optimal balance between climate risks and abatement costs. The naïve equilibrium ultimately reaches a peak of 570 ppmv, missing the 2000 stabilizations targets by a wide margin. Our results offer an explanation for the inertia in mitigation efforts over the past decades: policies often delay the majority of abatement efforts. Yet, believing that subsequent regulators will uphold the planned future efforts is self-defeating.

Supplementary material

10584_2015_1447_MOESM1_ESM.docx (60 kb)
ESM 1(DOCX 59 kb)

Copyright information

© Springer Science+Business Media Dordrecht 2015

Authors and Affiliations

  1. 1.Department of Economics, CentERTSC Tilburg UniversityTilburgNetherlands
  2. 2.New CollegeUniversity of Oxford and CPB Netherlands Bureau for Economic Policy AnalysisThe HagueNetherlands

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