American drivers bought 8.6 million SUVs in 2021, a 6% jump from the previous year, and global sales rebounded to reach a new record. The trend is undercutting efforts to reduce greenhouse gas emissions and slow climate change, analysts at the International Energy Agency warned.

If SUVs were a country, they would now be the world's sixth-largest carbon emitter, IEA Chief Energy Modeler Laura Cozzi and colleague Apostolos Petropoulos wrote in their Dec. 21 commentary.

More than 98% of SUVs on the road today use a combustion engine fueled by gasoline or diesel, making such vehicles a major contributor to energy-related carbon-dioxide emissions over the past decade. Because of their weight, SUVs consume about 20% more fuel than midsized cars.

At the same time, electric SUV models are gaining momentum in a market that could eventually shrink the carbon footprint of SUVs. In the U.S. and the European Union, e-SUVs are forecast to make up more than 55% of all EV sales in 2021, the IEA said. The ING research group has estimated that EVs will make up 14% of global vehicle sales this year, although the EV share of the U.S. market will only reach 4% of total sales.

The IEA has projected that nations must cut fuel consumption by 50% below 2005 levels over the next decade to meet carbon reduction targets under the Paris Agreement on climate change. The transportation sector emits more than any other sector in the U.S., and more than half of that pollution comes from SUVs and other passenger vehicles.

In all, an extra 35 million more SUVs were on roads worldwide in 2021 compared to 2020, sending an additional 120 million metric tons of CO2 emissions into the atmosphere. To rein in such climate-warming pollution, policymakers should provide market incentives to speed the adoption of EVs, the IEA researchers said.

The IEA analysis was released a day after the Biden administration finalized a new fuel economy rule that is expected to prompt carmakers to produce more emissions-free pickup trucks and SUVs to meet the more stringent, fleetwide requirements. Crossover utility cars and SUVs are the vehicle of choice for half of all American drivers.

The bipartisan infrastructure bill Biden signed into law in November also provided an initial $7.5 billion for EV charging infrastructure, and the now-imperiled Build Back Better legislation was supposed to provide even more support.

"Each of these pieces helps," said Joel Levin, executive director of the EV advocacy group Plug In America. "If the vehicles were cheaper, charging infrastructure made more accessible, and if fuel economy standards are tightened, it will certainly have an impact."

U.S. fuel economy improved 32% between 2004 and 2020, and the new mileage standards will achieve another 7% decline in fuel consumption by 2030, according to U.S. Environmental Protection Agency estimates. The cuts will still fall short of the IEA's goal to cut consumption in half, but the EPA's data does not take into account an expected growth in the EV market that will also reduce demand for combustion engines.