Carbon-Neutral Pathways for the United States

The Intergovernmental Panel on Climate Change (IPCC) Special Report on Global Warming of 1.5 degrees C points to the need for carbon neutrality by mid-century. Achieving this in the United States in only 30 years will be challenging, and practical pathways detailing the technologies, infrastructure, costs, and tradeoffs involved are needed. Modeling the entire U.S. energy and industrial system with new analysis tools that capture synergies not represented in sector-specific or integrated assessment models, we created multiple pathways to net zero and net negative CO2 emissions by 2050. They met all forecast U.S. energy needs at a net cost of 0.2-1.2% of GDP in 2050, using only commercial or near-commercial technologies, and requiring no early retirement of existing infrastructure. Pathways with constraints on consumer behavior, land use, biomass use, and technology choices (e.g., no nuclear) met the target but at higher cost. All pathways employed four basic strategies: energy efficiency, decarbonized electricity, electrification, and carbon capture. Least-cost pathways were based on >80% wind and solar electricity plus thermal generation for reliability. A 100% renewable primary energy system was feasible but had higher cost and land use. We found multiple feasible options for supplying low-carbon fuels for non-electrifiable end uses in industry, freight, and aviation, which were not required in bulk until after 2035. In the next decade, the actions required in all pathways were similar: expand renewable capacity 3.5 fold, retire coal, maintain existing gas generating capacity, and increase electric vehicle and heat pump sales to >50% of market share. This study provides a playbook for carbon neutrality policy with concrete near-term priorities.