Pre-pandemic levels of carbon dioxide emissions in 2021 after years of steady decline were due to coal and freight transportation, according to a recent report.

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.

Read more: