Understanding the potential of international agreements to mitigate cross-border environmental pollution is crucial to guide policymakers towards designing instruments that make a real difference. However, evaluating the effectiveness of international agreements on reducing emissions is difficult, principally because it is challenging to establish how emissions would have evolved in the absence of countries’ participation.

This paper examines the 1979 Convention on Long-Range Transboundary Air Pollution (LRTAP) and three subsequent protocols with the aim of identifying their effects on emissions. By combining a new global dataset on emissions with a methodology to construct counterfactual scenarios – how emissions would have evolved had the protocols not been ratified – the author provides new and arguably more credible evidence than before on the effects of the protocols.

Results from the analysis suggest that the international protocols in question have directly led to sizeable reductions in pollutants. The findings suggest that protocols of this kind can be an effective tool to induce countries to reduce their emissions.

Key points for decision-makers

  • The analysis examines the 1985 Helsinki protocol on sulphur dioxide (SO2) emissions, the 1988 Sofia protocol on nitrous oxides (NOx), and the 1991 Geneva protocol on volatile organic compounds (VOCs).
  • Previous examinations of these found no effect of the Helsinki protocol on SO2 emissions, and significant but small reductions in NOx emissions induced by the Sofia protocol. The Geneva protocol had not been examined prior to this study.
  • The results from this study suggest that for ratifying countries of the Helsinki protocol, SO2 emissions were on average 22% lower than in the synthetic control group 10 years after the intervention.
  • Emissions of NOx were 18% lower for countries that ratified the Sofia protocol after 10 years, compared with the control group.
  • For VOCs, emissions were 20% lower for ratifying countries of the Geneva protocol after 10 years, compared with the control group.
  • These positive results contrast with the often negative predictions made by the game theory literature, which say that free-riding incentives will render such agreements ineffective where enforcement mechanisms are lacking. (In other words, self-interested countries will have an incentive to rely on the emissions reductions of others without playing their part, and in this way enjoy the trans-border benefits without incurring associated costs.)
  • The author also discusses methodological challenges that can lead to biased estimates, and ways to overcome these, and shows that previous empirical studies on the Helsinki protocol have tended to underestimate its favourable effects on reducing SO2.
  • The author highlights further challenges in estimating the impacts of international protocols within a complex, globalised economy. These include emissions leakage: where countries reduce their emissions within their own borders, this could lead to increased emissions, via trade flows, in countries that have not ratified a protocol.
  • At the same time, greater adoption of technology by ratifying countries might stimulate technological development and diffusion, potentially leading to emissions reductions in non-ratifying countries too.
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