USA

Historical emissions are based on the 1990–2022 inventory emissions developed by the US Environmental Protection Agency (EPA) (U.S. Environmental Protection Agency, 2024k). The national inventory was reported in AR5 Global Warming Potential (GWP) values. We converted all values to AR4 GWP.

2030 NDC target

For the 2030 NDC target, we apply the indicated target of 50%–52% reduction to the 2005 base year including LULUCF, and then subtract the projected emissions for the LULUCF sector. The LULUCF emission projections in 2030 were taken from the 5th Biennial Report which reported sinks of 0.6–0.8 GtCO₂e/year in 2030 (U.S. Department of State, 2022).

2050 net zero target

For the net zero target, we assume total GHG emissions in 2050 are balanced by projected sinks in 2050. The LULUCF sinks in 2050 were taken from the US long-term strategy (LTS) submitted to the UNFCCC in November 2021 (U.S. Department of State, 2021). Since the document does not provide exact figures, we have extracted the approximated figures from the graphs in the report. The reading of the graphs results in an approximation of minus 0.6-1.4 GtCO₂e/year for LULUCF sinks in 2050, we add this sink to the residual estimate in 2050 to get 0.6-1.5 GtCO₂e/year in 2050. We include also estimates for 2040 in our pathway using a similar approach.

The current policy projections were generated in five steps:

• First, we estimate the total emissions projections under current policies as the aggregation of the energy, industry, agriculture, and waste sectors:
  • GHG emissions in the energy sector:
    • Energy-related CO₂ emissions projections: short-term projections (2023–2025) were taken from the US Energy Information Agency’s (EIA) Short-term Outlook from August 2024 (U.S. Energy Information Administration, 2024e). These projections are harmonised with long-term projections (2024–2035) taken from a model comparison study by the US Environmental Protection Agency (EPA) (U.S. Environmental Protection Agency, 2023d) . The modelling comparison study includes the implementation of the Inflation Reduction Act (IRA). It represents the upper range of emissions projections.
    • Non-CO₂ emissions in the energy sector from EPA’s U.S. State-level Non-CO₂ Greenhouse Gas Mitigation Potential: 2025–2050 (U.S. Environmental Protection Agency, 2022b).
    • All GHGs emissions in the energy sector result from the sum of the CO₂ and non-CO₂ estimates as described above. The resulting projections are harmonised to the latest historical year using growth rates.
  • GHG emissions from industrial processes: the projection of GHG emissions in industrial processes was calculated by type of industry and then aggregated.
    • GHG emissions in the mineral, chemical, and metal industries were projected by applying projected production growth of each industry in terms of value of shipments taken from EIA’s Annual Energy Outlook 2023 (U.S. Energy Information Administration, 2023f), to their respective GHG emissions in the base year. We use two scenarios from the Annual Energy Outlook—the reference scenario and the low economic growth scenario—to create a range of emissions projections.
    • To project the rest of industry processes, we apply the growth rates from industrial process F-gas emissions from the EPA’s U.S. State-level Non-CO₂ Greenhouse Gas Mitigation Potential: 2025–2050, which includes policies that were implemented until early 2015 (U.S. Environmental Protection Agency, 2022b).
  • GHG emissions in the agriculture and waste sectors follow the growth rates of the respective sector in the EPA’s U.S. State-level Non-CO₂ Greenhouse Gas Mitigation Potential: 2025–2050 (U.S. Environmental Protection Agency, 2022b). We did not consider alternative economic growth scenarios for GHG emissions in the agriculture and waste sectors.
• Second, each of the above emissions categories was harmonised to historical data for each sector by applying the estimated annual percentage change from the projected dataset to the base year. The projections for all sectors were then aggregated to obtain total GHG emissions, excluding LULUCF. These projections are the baseline scenarios.
• Third, the quantification of the Inflation Reduction Act (IRA) in non-CO₂ emissions and in non-energy sectors:
  • Non-CO₂ emissions: The IRA has the potential to reduce non-CO₂ GHG emissions. The quantification of such impact is based on the assessment of this policy on total GHG emissions (Zero Lab, 2024). We use the mitigation potential range of the current policy scenario (including the IRA) compared to the frozen policy scenario (not including the IRA) on non-CO₂ emissions reported for years 2030 and 2035 and made a linear interpolation for the years in between and zero for 2022. The mitigation potential is subtracted from the baseline scenario emissions, whereby the mitigation effect is 90–100 MtCO₂e in 2030 and 80–90 MtCO₂e in 2035.
  • Non-energy CO₂ emissions: The IRA also has the potential to reduce CO₂ emissions in non-energy sectors, mainly in Industry Processes and Product Use (IPPU), which are not quantified in the baseline scenarios. We assume that such emissions reductions will be achieved mainly through Carbon Capture, Utilisation, and Storage (CCUS). The quantification of such impact is based on the assessment of IRA on mitigation potential of CCUS in the study conducted by King, Gaffney, et al. (2024). We assume a range of mitigation potential between zero, to capture the uncertainty around the deployment of CCUS, and the mitigation potential reported in 2030 and 2035, assuming a start of emissions reduction in 2025. We carried out a linear interpolation for the years in between. The resulting mitigation potential for each year is subtracted from the baseline scenarios emissions, resulting in a reduction of the emissions level of up to 77 MtCO₂e in 2030 and 85 MtCO₂e in 2035.
• Fourth, the quantification of the AIM Act, which was not part of the policies considered in the baseline scenario taken from Global Non-CO₂ Greenhouse Gas Emission Projections & Mitigation Potential:
  • Phase down of the production and consumption of hydrofluorocarbons (HFCs) by 85% over the next 15 years. The annual mitigation potential is calculated as a range of between two mitigation potential trajectories for HFC emissions:
    • The first mitigation potential trajectory is based on the HFC emissions projection reported in the 5th Biennial Report in 2020, 2030, 2035, and 2040 (U.S. Department of State, 2022), which considers the implementation of the AIM Act, although does not achieve the proposed target. After harmonising the projections with the latest historical year, we interpolated the years in between and calculated the annual mitigation potential against the baseline scenario.
    • The second is based directly on the annual HFCs consumption caps defined in the AIM Act (U.S. Environmental Protection Agency, 2021a). We then calculated the mitigation potential against the baseline scenario.
  • The resulting mitigation potential range for each year is subtracted from the baseline scenario emissions, resulting in a reduced emission levels of 50–150 MtCO₂e in 2030 and 100–200 MtCO₂e in 2035.
• Fifth, economy wide emission projections from a 2024 study by the Rhodium Group (King, Kolus, et al., 2024) were included in the analysis as well, after deducting LULUCF sinks based on the 5th BUR. The study includes additional policies, including the impact of the EPA's emissions standards for vehicles beginning in model year 2027 (U.S. Environmental Protection Agency, 2024i) and the EPA's pollution standards for fossil fuel power plants (U.S. Environmental Protection Agency, 2024m). This study represents the lower end of the current policy projections range.