Climatic Change

, Volume 132, Issue 4, pp 519–529 | Cite as

Moving targets—cost-effective climate policy under scientific uncertainty

  • Reyer Gerlagh
  • Thomas O. Michielsen


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.


Climate Policy Carbon Price Integrate Assessment Model Cumulative Emission Stabilization Target 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Author contributions

RG wrote the code for the GAMS model and STATA figures. RG and TM both contributed to the final text.

Conflict of interest

The authors declare that they have no competing interests.

Supplementary material

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


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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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