What is United States's pathway to limit global warming to 1.5°C?

Under the HPA scenario, enhanced electrification results in significant energy savings due to the increased energy efficiency offered by electricity as a fuel. Total sector energy demand will fall by 56% by 2040 and by 70% by 2050 compared to 2023 levels. Accelerating electrification and shifting transport would greatly reduce reliance on inefficient and costly fossil fuels and shield consumers from the impacts of price fluctuations in highly globalised fossil fuel markets.⁸8

Biofuels are projected to play a greater role in the US transport sector through 2050 – they can be used to reduce the carbon intensity of the remaining ICE fleet on the road until full penetration of EVs has been achieved. Biofuels also have applications in so-called hard-to-abate sectors like aviation and shipping. However, due to the sustainability and scalability limitations of biofuels, their use should be limited, and policies should set strict eligibility criteria to prevent competition for crops and land. In the United States, biofuels production already consumes over half of all soybean oil produced.⁹9 Soybean farming drives significant soil and water degradation, with increased demand for biofuels expected to cause further negative impacts without sufficient regulatory action.¹⁰10

In the HPA scenario, synthetic fuels will play a major role in long-distance aviation and maritime transport, given the technological limitations of battery use in these modes, gaining momentum from 2040 onward.

Transportation and urban planning policy in the United States has been a tool for economic, social and racial segregation, prioritising the status quo of passenger vehicles and traditional combustion engines over electric vehicles (EVs), public mass transit and active modes like walking and cycling.¹¹11^,1212 National level transportation policy under the second Trump administration mirrors other sectors, focusing on deregulation, cutting funding for mass transit and decarbonisation, and supporting only ICE vehicles.¹³13^{, 14}14^{, 15}15

Without decisive action and funding at the Federal level, fundamental restructuring of the mobility system is unlikely, although progressive states and cities continue to take steps to decarbonise transport. New York City introduced congestion pricing measures for its most congested areas, which has so far brought more revenue than anticipated while increasing foot traffic, decreasing local pollution and boosting public transit ridership.¹⁶16^{, 17}17 At the state level, California continues to act as a climate policy leader, with more ambitious vehicle emissions standards, a 100% zero emission vehicle target for 2035, and a number of consumer incentives for the purchase of EVs in addition to policies supporting active modes of transport.¹⁸18 As of 2024, zero emission vehicles made up roughly 6% of total registered LDVs in California, with 1.9 million on the road.¹⁹19