High-ambition climate action in all sectors can achieve a 65% greenhouse gas emissions reduction in the United States by 2035

The Paris Agreement seeks to limit warming to 1.5 °C, requiring countries to periodically update near-term NDCs and articulate long-term net-zero strategies. Current 2030 NDCs are insufficient for the long-term goal, making enhanced ambition for 2035 essential. As the world’s largest economy and second-largest GHG emitter, the United States is pivotal to global success. The U.S. NDC pledges a 50–52% reduction below 2005 levels by 2030 and a long-term net-zero by 2050. Recent federal actions, notably the Inflation Reduction Act (IRA) of 2022 and the Bipartisan Infrastructure Law (BIL) of 2021, mobilize over $1 trillion for clean energy, carbon management, and infrastructure and are estimated to reduce emissions by 33–40% by 2030. Subnational actors—states, cities, and others—have also driven ambition via renewable electricity targets and EV sales policies. This study assesses pathways to a maximally ambitious U.S. 2035 NDC using a state-resolved integrated assessment model, evaluating current policies and an Enhanced Ambition scenario spanning all sectors and gases.

The study employs GCAM-USA-CGS, an updated, state-level version of the GCAM integrated assessment model, calibrated to the latest renewable energy costs and U.S. EPA non-CO2 marginal abatement cost curves. GCAM-USA-CGS represents energy supply (coal, gas, oil, renewables, bioenergy), conversion (refining, power generation), and end-use sectors (buildings, transportation, industry), and tracks CO2 and non-CO2 GHGs across energy, agriculture, land use, and other systems. Policies are modeled at national and state levels, with dynamic cross-sector feedbacks, and results are harmonized to the EPA inventory using AR6 100-year GWPs. Two scenarios are analyzed: (1) Current Policies, including existing federal policies (IRA, BIL provisions; existing CAFE/GHG standards) and non-federal actions (state RPS, EV incentives), and (2) Enhanced Ambition, which builds on Current Policies with more stringent federal and state measures. Enhanced Ambition incorporates proposed federal regulations for fossil power plants (Clean Air Act §111(b)/(d)), accelerated ZEV adoption for LDVs, buses, and freight trucks, strengthened zero-emission appliance and efficiency standards in buildings, comprehensive methane abatement (including a methane fee covering all sources), LULUCF enhancements, and extensions/expansions of IRA tax credits beyond legislated sunsets. States are tiered by existing ambition: Tier 1 (e.g., CA, CO, NY) adopt the most ambitious standards (ACC/ACT EV sales, zero-emission appliances); Tier 2 increase ambition on a delayed schedule; Tier 3 implement minimal changes. A sensitivity analysis varies key drivers (GDP, population, oil/gas prices, solar/wind costs, and land sink potential) to quantify a range of emissions outcomes around central scenarios. Detailed sectoral policy representations are summarized in a comparative table and elaborated in Supplementary Notes, with power sector coal phaseout by 2030 under Enhanced Ambition and no new unabated fossil infrastructure in industry. Model inputs are publicly available; outputs are reproducible with GCAM 6.0 release and the provided input set.

• Under Current Policies, U.S. net GHG emissions fall 44% below 2005 levels by 2035 (range: 37%–52%). Under Enhanced Ambition, reductions reach 65% by 2035 (range: 59%–71%). • Enhanced Ambition achieves 53% GHG reductions by 2030 (upper end of the current NDC range) and maintains rapid decarbonization to 2035. • Sectoral contributions to 2030–2035 reductions (Enhanced Ambition): electricity delivers the largest absolute cut (reported as 1370 MtCO2) for 47% of total; transportation contributes 26% (reported 76 MtCO2); buildings, industry, and methane together contribute 29% (reported 207, 132, and 239 MtCO2 respectively); the “other” category (DAC, LULUCF, other gases) contributes the remaining 7%. • Power sector: By 2035, generation mix reaches 57% renewables and 96% clean under Enhanced Ambition (vs 50% renewables, 78% clean under Current Policies). All unabated coal-fired generation is phased out by 2030 under Enhanced Ambition; state RPS targets are enhanced (≥75% by 2035 in Tier 1; 55% in Tier 2; 20% in Tier 3), and federal §111(b)/(d) standards are included. • Transportation: Emissions decline 48% below 2020 by 2035 under Enhanced Ambition (vs 33% under Current Policies). LDV EV sales reach 83% by 2035 (vs 45% Current Policies); freight truck EV sales reach 42% by 2035 (more than double Current Policies). LDV stock is 42% electric nationally by 2035 (state range 25%–57%). VMT grows only 9% from 2020 to 2035 under Enhanced Ambition (vs 28% under Current Policies) due to VMT-reduction policies. • Buildings: Emissions drop 38% from 2020 to 2035 under Enhanced Ambition (207 MtCO2e) vs 16% (85 MtCO2e) under Current Policies, driven by IRA extensions, zero-emission appliance standards, and strengthened efficiency mandates/EERS. • Industry: Emissions fall 12% from 2020 to 2035 (132 MtCO2) under Enhanced Ambition, versus a 4% increase (43 MtCO2) under Current Policies; includes no new coal, high-ambition industrial CCS, with 77 MtCO2 sequestered in cement/ethanol/pulp under Enhanced Ambition (vs 5 MtCO2 under Current Policies). • Methane: With a fee covering all sources (including agriculture and waste) and strengthened policies, methane emissions decrease 30% (239 MtCO2e) from 2020 to 2035 under Enhanced Ambition, versus 5% (41 MtCO2e) under Current Policies. • Carbon removal and land: LULUCF sink reaches −926 MtCO2 in 2035 under Enhanced Ambition (increase of 73 MtCO2 from 2020), versus −882 MtCO2 under Current Policies. DAC reaches 31 MtCO2/y by 2035 under Enhanced Ambition (introduced after 2030). BECCS sequesters over 100 MtCO2/y by 2035 under Enhanced Ambition (vs 4 MtCO2/y under Current Policies).

The 2030–2035 period is a pivotal transition toward U.S. net zero, requiring deepening decarbonization beyond the power and transport sectors into buildings, industry, methane abatement, and land. While continued rapid deployment of low-cost renewables and EVs is central, achieving a 65% reduction by 2035 necessitates accelerated policies across all sectors. Key challenges include scaling EV charging infrastructure (especially for freight and across states), addressing critical mineral supply risks, overcoming building electrification barriers (legacy building stock, higher upfront costs, codes, and consumer perceptions), and managing industrial high-heat applications. Power sector decarbonization faces interconnection backlogs (>1 TW of clean capacity in queues), insufficient transmission, and permitting delays; reforms to siting, permitting, and utility business models are needed to align incentives with climate goals. Demand-side measures (efficiency, VMT reduction, demand response, flexible EV charging) can moderate load growth and enhance grid flexibility. Rapid diffusion of emerging technologies (CCS, DAC, BECCS) will require cost reductions, robust policy support, and social acceptance. Policy durability is a concern: governance, public support, and potential rollbacks create uncertainty, though investment-led policies (e.g., IRA) tend to be more resilient. Embedding ambition at multiple government levels can enhance robustness; federal incentives can advance clean energy even in low-regulation states. Overall, the results indicate a plausible, though challenging, pathway to a 2035 NDC aligned with a 1.5 °C trajectory if implementation is accelerated.

This study charts a plausible high-ambition pathway for the United States to reduce net GHG emissions 65% below 2005 levels by 2035 through coordinated federal and non-federal action across all sectors. Current Policies alone achieve a 44% reduction by 2035, underscoring the need for enhanced measures such as coal phaseout by 2030, accelerated ZEV adoption (LDVs, freight, buses), strengthened building electrification and efficiency standards, comprehensive methane abatement, industrial CCS, and expanded carbon removals (LULUCF, DAC, BECCS). Realizing this pathway requires expedited permitting, transmission build-out, utility regulatory reform, infrastructure investment, and targeted support for disadvantaged communities. The modeling framework and public datasets enable replication and state-level analysis to inform NDC design. Future research should deepen assessment of policy durability, social acceptance, infrastructure constraints (interconnection and transmission), critical minerals supply chains, and subnational implementation pathways, as well as explore alternative technology and behavioral scenarios and their system interactions.

The analysis does not fully capture political, social, and behavioral uncertainties that affect policy enactment, uptake, and durability. Model limitations include simplified representation of transmission and distribution build-out and interconnection constraints, which are critical for power sector decarbonization. Some policy implementations (e.g., IRA tax credits) are assumed to be fully effective, whereas real-world uptake may lag. Technology deployment assumptions for CCS, DAC, and BECCS depend on future cost reductions, regulatory frameworks, and public acceptance. Sensitivity analyses cover only a subset of drivers (macroeconomics, fuel prices, renewable costs, land sink potential), leaving residual uncertainty. Potential policy rollbacks and heterogeneity in state-level implementation introduce additional risks to achieving modeled outcomes.