A research roadmap for quantifying non-state and subnational climate mitigation action


Non-state and subnational climate actors have become central to global climate change governance. Quantitatively assessing climate mitigation undertaken by these entities is critical to understand the credibility of this trend. In this Perspective, we make recommendations regarding five main areas of research and methodological development related to evaluating non-state and subnational climate actions: defining clear boundaries and terminology; use of common methodologies to aggregate and assess non-state and subnational contributions; systematically dealing with issues of overlap; estimating the likelihood of implementation; and addressing data gaps.

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Fig. 1: Different ways of comparing city non-state climate action with state targets.
Fig. 2: Overview of key data missing for selected actors participating in transnational climate initiatives or reporting to city climate action platforms.

Data availability

The data and R script to produce Fig. 2 are available upon request from the authors of this study.


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We thank participants at an April 2017 workshop held at University College London in London, UK, as well as a November 2017 workshop in Bonn, Germany, who provided feedback on early thinking and drafts of this paper. This work was funded by ClimateWorks Foundation grant no. 17-1101.

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A.H., N.H., T.K., M.R., A.W., Y.X. and K.L. conceived the concept and led the analysis and writing. All other authors substantially contributed suggestions, ideas and writing.

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Correspondence to Angel Hsu.

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Hsu, A., Höhne, N., Kuramochi, T. et al. A research roadmap for quantifying non-state and subnational climate mitigation action. Nature Clim Change 9, 11–17 (2019). https://doi.org/10.1038/s41558-018-0338-z

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