Environment & energy — United States · Synthesis

The world's second-largest emitter. The United States emits on the order of 5,500 to 6,000 MtCO2e per year (EPA/EIA), the second-largest volume in the world after China, but about half as much as it. Relative to population, US emissions (≈ 17-18 tonnes per capita) are among the highest of the large countries.

Emissions on a downward trend. Emissions have fallen back from their mid-2000s peak, mainly thanks to the replacement of coal with gas (shale gas revolution) then by renewables in electricity generation. This decline has been driven largely by the market, without a unified and durable federal climate policy.

An electricity mix in transition. Coal has fallen sharply in favour of natural gas (the leading item) and renewables (wind, solar), whose share is rising quickly (≈ 21-23% of electricity). Nuclear remains a stable component. The carbon intensity of electricity is falling but remains higher than that of heavily decarbonized countries.

The Inflation Reduction Act, an industrial turning point. The Inflation Reduction Act (2022) triggered massive investment in low-carbon technologies (batteries, solar, hydrogen, electric vehicles) via tax credits. It is the main federal climate policy, whose effects on emissions will materialize gradually.

Other environmental issues. Beyond climate, the United States tracks air quality (improving over the long term), water, and is exposed to costly extreme weather events (hurricanes, wildfires, droughts) whose frequency and cost are rising (NOAA).

A climate policy subject to political swings. The absence of a structuring and stable climate law makes the US trajectory very sensitive to political cycles (joining or withdrawing from the Paris Agreement, EPA regulations contested in court). This is the main uncertainty in the outlook.

The dynamics of the IRA. The investments triggered by the Inflation Reduction Act, largely carried by the private sector and concentrated in certain states, have their own inertia. Their scale conditions the continued decline of emissions, independently of federal political vagaries.

Electrification and renewables. Continued decarbonization runs through the electrification of uses (transport, heating, industry) and the rise of renewables, which runs up against grid connection delays and permitting constraints.

Adaptation to climate extremes. The rising cost of natural disasters (insurance, infrastructure) makes adaptation a growing economic issue, managed largely at the level of states and local authorities.

The open questions. Three issues will shape the decade: (1) stabilizing a climate policy subject to political swings; (2) accelerating renewables and the grid; (3) reducing per-capita emissions, among the highest of the large countries.

Placed in their environment, the United States is a major emitter, high per capita, whose emissions are falling but remain far from the path to neutrality, within an unstable political framework.

Three takeaways. (1) Volume: second in the world. At ≈ 5,500-6,000 Mt, the United States emits about half as much as China (≈ 12,000+ Mt) but far more than the European Union (≈ 3,000 Mt) or India as a whole.

(2) Per capita: among the highest. US per-capita emissions are markedly higher than those of the European Union, Germany, the United Kingdom and especially France (low-carbon thanks to nuclear) — an effect of lifestyle, the vehicle fleet and the energy mix.

(3) A market-driven decline. Unlike the European Union, which reduces its emissions via a binding regulatory framework, the United States has mainly reduced them through market factors (gas, competitive renewables) — a more volatile and less steered trajectory.