Many countries have implemented national climate policies to accomplish pledged Nationally Determined Contributions and to contribute to the temperature objectives of the Paris Agreement on climate change. In 2023, the global stocktake will assess the combined effort of countries. Here, based on a public policy database and a multi-model scenario analysis, we show that implementation of current policies leaves a median emission gap of 22.4 to 28.2 GtCO 2 eq by 2030 with the optimal pathways to implement the well below 2°C and 1.5°C Paris goals. If Nationally Determined Contributions would be fully implemented, this gap would be reduced by a third. Interestingly, the countries evaluated were found to not achieve their pledged contributions with implemented policies (implementation gap), or to have an ambition gap with optimal pathways towards well below 2°C. This shows that all countries would need to accelerate the implementation of policies for renewable technologies, while efficiency improvements are especially important in emerging countries and fossilfuel-dependent countries.

Christopher (2019) A research roadmap for quantifying non-state and subnational climate mitigation action. Nature Climate Change, 9. pp. 11-17.

This article quantifies the net aggregate impact in 2030 of commitments by individual non-state and subnational actors (e.g. regions, cities and businesses, collectively referred to as 'NSAs') to reduce greenhouse gas (GHG) emissions. The analysis was conducted for NSAs operating within ten major emitting economies that together accounted for roughly two-thirds of global GHG emissions in 2016. Our assessment includes 79 regions (e.g. subnational states and provinces), approximately 6,000 cities, and nearly 1,600 companies with a net emissions coverage of 8.1 GtCO 2 e/year, or a quarter of the ten economies' total GHG emissions in 2016. The analysis reflects a proposed methodology to aggregate commitments from different subnational (i.e. regional and city government) and non-state (i.e. business) actors, accounting for overlaps. If individual commitments by NSAs in the ten high-emitting economies studied are fully implemented and do not change the pace of action elsewhere, projected GHG emissions in 2030 for the ten economies would be 1.2-2.0 GtCO 2 e/year or 3.8%-5.5% lower compared to scenario projections for current national policies (31.6-36.8 GtCO 2 e/year). On a country level, we find that the full implementation of these individual commitments alone could result in the European Union and Japan overachieving their nationally determined contributions (NDCs), while India could further overachieve its unconditional NDC target. In the United States, where the national government has rolled back climate policies, NSAs could become a potential driving force for climate action. Key policy insights. Full implementation of reported and quantifiable individual commitments by regions, cities and businesses (NSAs) in ten major economies could reduce emissions by 3.8%-5.5% in 2030 below current national policies scenario projections.. National governments' mitigation targets could be more ambitious if they would take NSA commitments into account. With full implementation of such action, the European Union and Japan would overachieve their NDC targets. For the United States such action could help meeting its original 2025 NDC target in spite of rollbacks in national climate policies.. The full universe of NSA climate action expands far beyond the subset of commitments analysed in this study; NSAs could become a strong driving force for enhanced action towards the Paris climate goals.

In the Paris Agreement under the United Nations Framework Convention on Climate Change (UNFCCC), for the first time, non-state actors were addressed in the international negotiations and were explicitly invited to act on climate change. Indeed, there are many transnational emission reduction initiatives (TERIs) outside the UNFCCC, driven by non-state actors or national governments, which aim at reducing greenhouse gas (GHG) emissions. Using an Integrated Assessment Model (IAM), this study assessed the potential impact of a selection of large TERIs that existed before the Paris Agreement on global greenhouse gas emissions. TERIs could lead to significant emission reductions: the eleven selected initiatives included in the analysis here couldif fully implementeddeliver annual GHG emission reductions of 2.5 GtCO 2 eq by 2020 and of 5.0 GtCO 2 eq by 2030 from a no-policy-baseline emission level of 53.7 GtCO 2 and 61.1 GtCO 2 eq, respectively. Although these reductions are of similar magnitude as those pledged by countries under the umbrella of the UNFCCC, these reductions may significantly overlap with those of pledges and Nationally Determined Contributions. The maximum estimate of overlap is around 70% by 2020 and 80% by 2030. This means that the combined impact on global GHG emissions of TERIs and NDCs, assuming a maximum overlap, would lead to emission levels between 53 and 55 GtCO 2 eq by 2030, compared to a level of 54 to 56 GtCO 2 eq resulting from NDCs alone.

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China has announced its intention to peak CO 2 emissions by 2030 or earlier. The peak in greenhouse gas emissions would reach 35-40% above 2010 levels. Current policies are likely not to be sufficient to meet the announced 2030 target. The expected emission levels reach about 50% above 2010 levels. Our selected enhancement policy measures lead to peaking CO 2 emissions before 2030.

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