US greenhouse gas emissions declined in 2016

Greenhouse gas emissions in the US dropped 1.9% in 2016 compared with 2015, the Environmental Protection Agency reported in an annual assessment released 18 April. The agency pinned at least some of the decline on an unusually warm winter in 2016 and utilities’ shift from coal to natural gas.

The 6.6 billion metric tons of carbon dioxide–equivalent gases that were spewed in 2016 also represented an 11% decline from their peak levels in 2007. The decade-long decrease was particularly pronounced in the electricity generation sector, where greenhouse gas emissions dropped by around 25%. The Energy Information Administration previously reported that 2016 was the first year that natural gas, which emits about half as much CO₂ as coal per unit of energy, surpassed coal as the country’s largest source of electricity. In addition to CO₂, which accounted for more than 80% of the total emissions, the EPA report measured methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons, sulfur hexafluoride, and nitrogen trifluoride.

The nearly 2% emissions decline, EPA administrator Scott Pruitt said in a statement , demonstrates that critics of the Trump administration’s decision to abandon “one-size-fits-all regulations like the Clean Power Plan or misguided international agreements like the Paris Accord” are wrong. “American ingenuity and technological breakthroughs, not top-down government mandates, have made the US the world leader in achieving energy dominance while reducing emissions—one of the great environmental successes of our time,” he said.

But the annual report covered calendar year 2016, when President Obama was in office. And the Obama-era Clean Power Plan, which Pruitt is trying to unravel, never took effect. Pruitt didn’t specify the technological breakthroughs that he referenced, but much of the technology development that led to the shale gas boom and has accelerated coal’s decline was funded by the federal government.

Also in 2016, transportation essentially tied electricity generation as the country’s largest source of greenhouse gases, the EPA reported. Relative to electricity, transportation’s share has been rising because the number of miles traveled by cars and light trucks has grown 45% since 1990. All those miles stem from population growth, economic growth, urban sprawl, and low fuel prices.

The EPA numbers align with the expectations of the nongovernmental organization Global Carbon Project, which releases an annual Global Carbon Budget. But GCP’s latest report, released last November, warns that both the US and the world may not be trending in the right direction. The organization projects only a 0.4% decline in US greenhouse gas emissions from 2016 to 2017, noting that US coal consumption edged up slightly for the first time in five years. Led by a 3.5% jump in China, global emissions were projected to rise 2% in 2017, ending a three-year period of zero emissions growth.