Historical emissions are based on the 1990–2020 National inventory report (US Government, 2022) , which is aligned with the inventory emissions developed by the US Environmental Protection Agency (U.S. Environmental Protection Agency, 2022b).
Emissions in 2021 were estimated on a sector-by-sector basis.
- Total GHG emissions in the energy sector were estimated for 2021 based the energy-related CO2 emissions reported in the May-2022 Energy Information Administration (EIA) monthly energy review, which is subject to higher uncertainty resulting from the impacts of Russia’s invasion of Ukraine (U.S. Energy Information Administration, 2022f), and non-CO2 emissions in the energy sector from the US State-level Non-CO2 Greenhouse Gas Mitigation Potential: 2025–2050 (US Environmental Protection Agency, 2022a). Total GHG emissions in the energy sector in 2021 were harmonised to 2020 using the growth rate of the sum of CO2 and non-CO2 emissions.
- The estimation of emissions in industrial processes was split by type of industry. GHG emissions in the mineral, chemical and metal industries were extended to 2020 using the growth rate of CO2 emissions in the industry sector in 2021 reported in the May-2022 EIA monthly energy review, which includes the impact of the Russian invasion of Ukraine as higher uncertainty (U.S. Energy Information Administration, 2022f). The remaining GHG emissions from industry processes followed the growth of the economy based on the GDP growth rate in 2021 (U.S. Bureau of Economic Analysis, 2022).
- GHG emissions in the agriculture and waste sectors were extended to 2021 using the trend of historical emissions in the last 5 years (2015–2019).
NDC and other targets
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 4th Biennial Report which reported sinks of 0.7–0.86 GtCO2e/year in 2030 (U.S. Department of State, 2021a).
The US submitted its 7th National Communication, the 3rd and 4th Biennial Report combined to the UNFCC on October 30 2021, after the lack of reporting under the previous US administration.
2050 Net-zero target
For the 2050 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, 2021b). 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.
Current policy projections
The current policy projections were done in four steps:
First, we estimate the baseline for 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 (2022–2023) were taken from the May-2022 EIA monthly energy review (U.S. Energy Information Administration, 2022f). These projections are harmonised with long-term projections (2023-–2030) from the EIA’s Annual Energy Outlook 2022(U.S. Energy Information Administration, 2022a), which includes all policies in place until the end of November 2021. 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.
- Non-CO2 emissions in the energy sector from the U.S. State-level Non-CO2 Greenhouse Gas Mitigation Potential: 2025-2050 (US Environmental Protection Agency, 2022b)
- All GHGs emissions in the energy sector result from the sum of the two points above (CO2 and non-CO2). The resulting projections are harmonised to the latest historical year using growth rates.
- Industrial processes GHG emissions: the projection of GHG emissions in industrial processes was split by type of industry
- 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 2022 (U.S. Energy Information Administration, 2022a), to their respective GHG emissions in the base year.
- Projections in the rest of industry processes apply the growth rates from industrial process F-gas emissions from the U.S. State-level Non-CO2 Greenhouse Gas Mitigation Potential: 2025-2050, which includes policies that were implemented until early 2015 (US Environmental Protection Agency, 2022b).
- We did not consider alternative economic growth scenarios for GHG emissions in industry processes.
- GHG emissions in the agriculture and waste sectors follow the growth rates of the respective sector in the U.S. State-level Non-CO2 Greenhouse Gas Mitigation Potential: 2025-2050 (US 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 were 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):
Fourth, the quantification of policies was incorporated in the baseline projections (which were not part of the policies considered in the baseline scenario taken from EIA’s Annual Energy Outlook 2022 and the Global Non-CO2 Greenhouse Gas Emission Projections & Mitigation Potential:
- Stricter fuel economy and GHG emissions standards for passenger vehicles for model years 2023–2026, reaching 52 miles per gallon (mpg) in 2026.
- The annual mitigation potential of greenhouse emissions until 2030 is directly extracted from the official impact assessment of the proposed rule. The rule estimates a reduction in emissions of 77 MtCO2e/yr in 2030 (ICCT, 2017)
- 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 linear interpolation between zero in 2022, year when the rule is expected to take place and 181 MtCO2e in 2036 (reflecting the 85% phase down in 15 years) (U.S. Environmental Protection Agency, 2021a).
Since the last assessment, the CAT has updated its methodology and pathways included for deriving modelled domestic pathways. As a result, there have been changes in the pathways for some countries, particularly for pathways that hold warming below 3°C. For the full CAT methodology click here.