U.S. emissions are decliningDespite the U.S. releasing the most cumulative emissions worldwide, its annual emissions are now less than China. During 2018, U.S. greenhouse gas emissions totaled 6.67 billion metric tons of carbon dioxide equivalent. The main source of greenhouse gas emissions in the U.S. is the energy sector, with carbon dioxide emissions from energy consumption amounting to 5.1 billion metric tons in 2019. However, this was a reduction of roughly one billion metric tons when compared to the peak emissions released in 2007. These reductions in energy related CO2 emissions coincide with the country’s move away from coal combustion, and its transition to natural gas and renewable energy sources such as wind and solar.
As greenhouse gas emissions have fallen in the U.S., so to have air pollutant emissions. For example, PM2.5 particulate matter concentrations have halved in the past three decades. This in turn has led to a reduction in the number of deaths attributable to air pollution.