Carbon dioxide emissions from the nation's power generators have been on the decline, even as the economy has grown—providing evidence that contradicts pro-coal arguments promoted by the Trump administration.
A report released Wednesday by the consulting firm M.J. Bradley & Associates finds that climate-warming carbon dioxide emissions from the country's power generators declined between 2005 and 2015 as the companies shifted away from coal and toward renewable energy sources and natural gas. Preliminary data from 2016 suggests that emissions dropped further last year, putting them at or near the same level they were in 1990. Meanwhile, the report notes, gross domestic product (GDP) has grown steadily over the same period.
"The decoupling of economic growth from emissions growth is really encouraging," said Dan Bakal, director of electric power for Boston-based sustainability advocacy group, Ceres, which sponsored the study. "You can achieve these reductions while growing the economy, and trying to reverse these trends would be an uphill battle."
The report looks at the 100 largest energy generators in the U.S. and compares generation data gathered from the U.S. Energy Information Administration with data from the U.S. Environmental Protection Agency on sulfur dioxide, nitrogen oxides, mercury and carbon dioxide, a greenhouse gas linked to climate change. Between 1990, when Congress passed major reforms to the Clean Air Act, and 2015, power plant emissions of all four fell. The report did not include methane, another important greenhouse gas.
While carbon dioxide emissions from the energy sector were 6 percent higher in 2015 than they were in 1990, they have fallen since their peak in 2007. In 2015, the sector's carbon dioxide emissions were 20 percent below 2005 levels.
Under the 2015 Paris climate agreement, the U.S. committed to cutting its total greenhouse gas emission, including from transportation and industry, 26-28 percent below 2005 levels by 2025. Earlier this month, President Donald Trump announced that he would pull the U.S. out of that accord, making good on his promise to "cancel" the Paris agreement.
Altogether, power producers' contributions to carbon dioxide emissions are dropping as a percentage of the whole, from being about 42 percent of all U.S. CO2 emissions in 2010 to 38 percent in 2015.
The shift comes as renewable energy sources—including hydroelectric, wind, solar, biomass, and geothermal—are contributing more to the energy mix.
"The majority of new capacity that's added is renewable," Bakal said, "and the shift away from coal has continued."
The country's top producers generate 85 percent of the country's electricity, but the sources of that electricity have shifted dramatically. In 2006, coal accounted for 52 percent of power production, and natural gas was 17 percent. In 2015, coal accounted for 34 percent, natural gas 32 percent.
Among the country's largest power producers, AEP generates the most CO2, according to the report—it gets 69 percent of its power from coal, but is only the sixth largest power producer, generating 137.8 million megawatt hours and 144 million tons of CO2. Duke, meanwhile, the country's largest energy producer, gets 35 percent of its mix from coal, generates 217.7 million megawatt hours, but generates less CO2—about 108 million tons.
The report found that country's largest CO2-emitting states are Texas, Florida and Pennsylvania. (Vermont, Idaho and Maine had the lowest total emissions.) But Wyoming, Kentucky and West Virginia had the highest CO2 emission rates because of their heavy reliance on coal.
In a separate report released on Wednesday, the U.S. Energy Information Administration detailed how wind and solar power had accounted for more than 10 percent of all U.S. electricity during the month of March. It was the first month in which wind and solar power exceeded 10 percent of generation, the EIA said.