Extending a decadelong trend of declining energy-related carbon dioxide emissions, U.S. energy-related CO2 emissions declined 1.7% in 2016 to total 5,170 million metric tons, according to a recent report from the U.S. Energy Information Administration.

U.S. energy-related CO2 emissions declined 2.7% between 2014 and 2015 and are now 14% below the 2005 level.

Helping to drive the reductions, both oil and natural gas consumption ticked higher in 2016, while coal consumption dropped significantly. The EIA said energy-related CO2 emissions in 2016 from petroleum and natural gas increased 1.1% and 0.9%, respectively, while coal-related emissions decreased 8.6%.

CO2 emissions from the electric power sector fell by 4.9% in 2016 as a significant reduction in coal use for electricity generation was offset by increased generation from natural gas and renewable sources.

"Renewables do not emit CO2, and a shift towards natural gas from coal lowers CO2 because natural gas has lower emissions per unit of energy than coal and because natural gas generators typically use less energy than coal plants to generate each kilowatthour of electricity," the agency said.

For the second year in a row, the carbon intensity of the power sector declined about 5%. "Since 1973, no two consecutive years have seen a decline of this magnitude, and only one other year (2009) has seen a similar decline," the EIA said.

Weather also affected energy use and CO2 emissions in 2016. Based on preliminary data, 2016 saw 10% fewer heating degree days than normal, indicating lower heating demand, and 13% more cooling degree days than normal, which indicates more cooling demand. Heating degree days in 2016 were the second fewest of any year since at least 1949, the agency said.

Showing the only uptick for any sector, CO2 emissions from the transportation sector increased by 1.9% in 2016, largely reflecting emissions from motor gasoline, which increased 1.8% in 2016. Emissions from the transportation sector surpassed emissions from the power sector during 2016, outlining a trend that is expected to persist through at least 2040, according to the reference case projections in the EIA's 2017 "Annual Energy Outlook."