Comparing emission mitigation pledges: Metrics and institutions

Abstract

A key element in the emerging international architecture will be practical mechanisms to compare domestic efforts to mitigate global climate change. How do countries decide whether and to what degree pledges by their peers – often expressed in different forms that stymie obvious apples-to-apples comparison – are sufficient to justify their own actions now and more ambitious actions in the future? We describe a number of desirable features of metrics that might be used for ex ante comparisons of proposed pledges and ex post assessments of subsequent actions delivering on those pledges. Such metrics should be comprehensive, measurable, and universal. In practice, however, no single metric has all these features. We suggest using a collection of metrics to characterise and compare mitigation efforts, akin to employing a suite of economic statistics to illustrate the health of the macroeconomy. We illustrate the application of a suite of metrics to several countries’ mitigation pledges (their intended nationally determined contributions in the UN climate talks). In the pledge and review model emerging in the climate change negotiations, participation, compliance, and ambition can be enhanced if this collection of metrics can illustrate comparable actions among peers, both prospectively and retrospectively. The latter, in particular, highlights the need for a well-functioning policy surveillance regime.