One of the largest and most developed countries in the world, the United States is also one of the worst polluters globally. The U.S. remains one of the world's top greenhouse gas emitters - currently behind China and India in total annual emissions - but it continues to lead all nations except China in cumulative historical output. According to the Environmental Protection Agency, U.S. greenhouse gas emissions were about 6.34 billion metric tons of CO₂-equivalent in 2022, and 2023 data showed a modest decline.