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

Current intended nationally determined contributions (INDCs) are insufficient to meet the Paris Agreement goal of limiting temperature change to between 1.5 and 2.0 °C above pre-industrial levels, 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.