Climate negotiations under scientific uncertainty

Abstract

How does uncertainty about "dangerous" climate change affect the prospects for international cooperation? Climate negotiations usually are depicted as a prisoners' dilemma game; collectively, countries are better off reducing their emissions, but self-interest impels them to keep on emitting. We provide experimental evidence, grounded in an analytical framework, showing that the fear of crossing a dangerous threshold can turn climate negotiations into a coordination game, making collective action to avoid a dangerous threshold virtually assured. These results are robust to uncertainty about the impact of crossing a threshold, but uncertainty about the location of the threshold turns the game back into a prisoners' dilemma, causing cooperation to collapse. Our research explains the paradox of why countries would agree to a collective goal, aimed at reducing the risk of catastrophe, but act as if they were blind to this risk.

Fig. 1.

Certainty model. Red area shows values for X and for which countries are collectively better off not avoiding catastrophe; here, . In the green area, catastrophe avoidance is a coordination game; here, . In the white area, avoiding catastrophe is a prisoners’ dilemma; here, if all other countries play , each country prefers to abate 0. With certainty, a prisoners’ dilemma arises only if b > 0.

Fig. 2.

Probability of catastrophe by treatment. Catastrophe was avoided 8 of 10 times in the Certainty treatment and 10 of 10 times under Impact Uncertainty (I-Uncertainty). In contrast, the probability of catastrophe was reduced below 100% (to 93%) by only 1 of 10 groups under Threshold Uncertainty (T-Uncertainty) and by only 3 of 10 groups (to 91, 86, and 80%, respectively) under Impact-and-Threshold Uncertainty (IT-Uncertainty). In the four cases where the probability of catastrophe was reduced below 100%, the spinning wheel determined that the threshold was crossed every time.

Fig. 3.

Pledges and actual contributions by treatment. In the Certainty and Impact Uncertainty treatments, pledges and contributions are tightly bunched, with contributions usually exceeding pledges. In the Threshold and Impact-and-Threshold Uncertainty treatments, values vary widely, with contributions usually falling far short of pledges. A small noise (3%) has been inserted to make all data points visible.