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Assessment of the climate commitments and additional mitigation policies of the United States


Current intended nationally determined contributions (INDCs) are insufficient1 to meet the Paris Agreement goal of limiting temperature change to between 1.5 and 2.0 °C above pre-industrial levels2, so the effectiveness of existing INDCs will be crucial to further progress. Here we assess the likely range of US greenhouse gas (GHG) emissions in 2025 and whether the US’s INDC can be met, on the basis of updated historical and projected estimates. We group US INDC policies into three categories reflecting potential future policies, and model 17 policies across these categories. With all modelled policies included, the upper end of the uncertainty range overlaps with the 2025 INDC target, but the required reductions are not achieved using reference values. Even if all modelled policies are implemented, additional GHG reduction is probably required; we discuss several potential policies.

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Figure 1: Baseline 2005 and 2025 greenhouse gas (GHG) emissions with uncertainties shown for each category of emissions.
Figure 2: Rank-ordered greenhouse gas (GHG) reduction estimates in 2025 by policy.
Figure 3: Estimated remaining 2025 greenhouse gas (GHG) emissions, target and emissions gaps by policy category.

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The authors thank D. Cullenward for early feedback on our approach, S. M. Donovan for research assistance on CH4 and N2O mitigation options, L. K. Price and J. Lin for guidance and feedback, and M. L. Fischer for comments on the manuscript. Work was supported by the Energy Foundation under US Department of Energy Contract No. DE-AC02-05CH11231.

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M.W. performed HFC policy analysis and comparison to prior studies; J.B.G. performed all other calculations and analysis. J.B.G. and M.W. wrote the manuscript and addressed reviewer concerns.

Corresponding author

Correspondence to Jeffery B. Greenblatt.

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The authors declare no competing financial interests.

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Greenblatt, J., Wei, M. Assessment of the climate commitments and additional mitigation policies of the United States. Nature Clim Change 6, 1090–1093 (2016).

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