U.S. carbon dioxide emissions boomeranged toward pre-pandemic levels in 2021, a turnaround from more than a decade of downward trends, and freight transportation and coal are major culprits, according to a report released Monday by the Rhodium Group, an independent research firm.

America’s greenhouse gas emissions grew 6.2 percent last year as the American economy largely recovered from pandemic lockdowns, the Rhodium report estimated. In comparison, between 2005 and 2019, U.S. emissions fell nearly 1 percent annually, on average, according to the Environmental Protection Agency. The uptick occurred largely due to a 17 percent jump in coal-fired power generation, the first annual increase in coal generation since 2014, and a rapid resurgence of road transportation. Coal’s comeback was driven largely by a hike in natural gas prices, which made coal power more economically attractive.

While last year’s emissions remained 5 percent below 2019 levels, the increase marks a reversal of early pandemic reductions.

The findings echo end-of-year emissions numbers from Carbon Monitor and the U.S. Energy Information Administration. Carbon Monitor, an academic group that tracks emissions, concluded U.S. emissions ramped up 7 percent through the end of October. A year-end report by the U.S. Energy Information Administration forecasted a 7 percent increase in energy-related CO2 emissions.

The transportation sector, which experienced the largest decline in greenhouse gas emissions in 2020, saw the largest increase in 2021 as demand, primarily for freight transport of consumer products and secondly for passenger travel, rebounded, the report said. However, even with the availability of Covid-19 vaccines, new variants and breakthrough cases led to staggered fuel demand. The sector’s 10 percent rise from 2020 emissions levels represents a recovery of about two-thirds of its drop from 2019 levels. 

The electric power sector, which comprises 28 percent of net U.S. emissions, experienced the second steepest emissions increase relative to 2020, despite a mere 3 percent increase in electric power demand. The sector’s 6.6 percent emissions hike was driven largely by a surge in natural gas prices, with Henry Hub spot prices averaging $4.93 per million Btu in 2021—more than double their 2020 rate. 

Oil and gas prices soared as producers reduced production last year in response to the Covid oil price collapse and the diminished demand that followed, Rhodium said. Higher prices made gas-fired generation less economical in 2021, leading to a 3 percent decline in gas generation in 2021.

Renewable energy generation growth slowed to half of its 2020 rate, but accounted for 20 percent of U.S. electricity generation for the first time. 

Industry emissions experienced the most modest drop in 2020 at 6.2 percent, but ticked up 3.6 percent in 2021—making up just over half the difference from 2019 levels. The buildings sector experienced the smallest rise in greenhouse gas emissions in 2021, growing only 1.9 percent from 2020, giving up a quarter of the drop in emissions from 2020. 

The trajectory of emissions this year remains uncertain. The Energy Information Administration estimates natural gas prices will plummet, but remain above pre-pandemic levels, causing coal generation to backslide to 22 percent of U.S. power production—1 percent lower than in 2021.

This year’s emissions increase sets the U.S. even further from its Paris Agreement goal of slashing emissions 50 to 52 percent below 2005 levels by 2030. In 2021, U.S. emissions rose to 17.4 percent below 2005 levels, despite hitting 22.2 percent below 2005 in 2020.

Without the Democrats’ Build Back Better bill, a $2.2 trillion spending and tax package that contains billions of dollars in renewable energy incentives, the U.S. is only on course for emissions reductions of roughly 30 percent by 2030. According to a Rhodium Group report, joint action by leading states, Congress and the executive branch can put the 2030 target within reach, but they must act quickly.

There are limited options for cutting carbon emissions in the short-term. Technological solutions such as carbon capture that reduce emissions by industry—responsible for nearly a quarter of CO2 released—are often expensive or unavailable, Scientific American reported. Renewable energy must compete in markets still dominated by fossil fuels, and American consumers typically wait years to replace high-emitting items like refrigerators or water heaters.

Within the transportation sector, which accounts for 31 percent of U.S. emissions, electric vehicle purchases grew to 435,000 in the first three quarters of 2021, compared with 320,000 EVs sold in the entirety of 2020, said Corey Cantor, an analyst who tracks the industry at Bloomberg New Energy Finance. However, EVs at this time cannot offset rising emissions from increased travel rates and non-electric passenger vehicles sales, according to an International Energy Agency report. The U.S. is on track to buy 8.6 million new SUVs in 2021, the report said.

Cantor predicted EVs could begin to make a dent in U.S. transportation emissions around 2025, when they are estimated to achieve cost parity with cars using internal combustion engines.

That leaves much of the short-term carbon-cutting to the power sector, which has done the bulk of greening America’s economy in recent decades. After retiring less than 5 gigawatts of coal capacity in 2021, some 12 gigawatts of coal capacity are slated to be retired this year, according to Energy Information Administration figures.

Ariel Gans is a graduate student at Northwestern’s Medill School of Journalism, specializing in politics, policy and foreign affairs reporting. She received a B.A. in Political Science and a B.S. in Society & Environment from the University of California, Berkeley. Her work has appeared in USA Today, OpenSecrets, Sierra Magazine, UPI and the Bay City Beacon.