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An experimental investigation into ‘pledge and review’ in climate negotiations


A novelty of the new Paris Agreement is the inclusion of a process for assessment and review of countries’ nationally determined pledges and contributions. The intent is to reveal whether similar countries are making comparable pledges, whether the totality of such pledges will achieve the global goal, and whether, over the coming years, the contributions actually made by countries will equal or exceed their pledges. The intent is also to provide an opportunity for countries to express their approval, or disapproval, of the pledges and contributions made by individual countries. Here we report the results of a lab experiment on the effects of such a process in a game in which players choose a group target, declare their individual pledges, and then make voluntary contributions to supply a public good. Our results show that a review process is more likely to affect targets and pledges than actual contributions. Even when a review process increases average contributions, the effect is relatively small. As the window for achieving the 2 °C goal will close soon, our results suggest that, rather than merely implement the Paris Agreement, negotiators should begin now to develop complementary approaches to limiting emissions, including the adoption of agreements that are designed differently than the one adopted in Paris.

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  1. 1.

    We refer specifically to the 12 February 2015 text of the Ad Hoc Working Group on the Durban Platform for Enhanced Action, available at

  2. 2.

    The game-theoretic model underlying our experiment is a specific representation of a more general theoretical model (Barrett 2013), and has been used in previous experimental investigations (Barrett and Dannenberg 2012, 2014). For details, see our electronic supplementary materials. For different but related experiments on “dangerous” climate change, see Milinski et al. (2008), Tavoni et al. (2011), and Dannenberg et al. (2015).

  3. 3.

    The first five groups played the game with an endowment fund of €15. However, payoffs turned out to be lower than we expected, and so we increased the endowment fund to €19 for the remaining groups. Statistical tests show that this change did not affect the participants’ behavior in the game (Whitney-Wilcoxon rank-sum test, P > .10 for the chosen targets, pledges, and contributions).

  4. 4.

    We aimed to have 10 groups per treatment, but due to no-shows in one session, only nine groups played the Mid-Point-Review treatment.

  5. 5.

    Contributions relative to the monetary endowment (in our experiment, the value of all chips given to a player at the start of the game), ranges from 46 % (No-Review) to 60 % (Ex-Post-Review), which is close to what has been observed previously in one-shot public goods games (Ledyard 1995).

  6. 6.

    As one of our reviewers pointed out, the difference in contributions between No-Review and Ex-Post-Review is weakly significant according to a one-sided t-test (P = 0.086). The results for all other comparisons remain qualitatively unchanged using either a two-sided or one-sided t-test instead of the non-parametric MWW test.


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We thank Alessandro Tavoni and two anonymous reviewers for comments and James Rising for developing the software for our spinning wheel. We are also grateful to the Magdeburg Experimental Laboratory for Economic Research team at Magdeburg University for support in conducting the experiment. This work was supported by the Princeton Institute for International and Regional Studies research community on Communicating Uncertainty: Science, Institutions, and Ethics in the Politics of Global Climate Change and the European Research Council (ERC) Starting Grant “Human Cooperation to Protect the Global Commons” (HUCO, Project Number: 636746).

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Correspondence to Scott Barrett.

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Barrett, S., Dannenberg, A. An experimental investigation into ‘pledge and review’ in climate negotiations. Climatic Change 138, 339–351 (2016).

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  • Payoff
  • Review Process
  • Free Rider
  • Paris Agreement
  • Review Mechanism