After declining for two consecutive years, greenhouse gas emissions in the U.S. jumped by 2 percent in 2013 over the previous year, according to a report released Thursday by the U.S. Environmental Protection Agency (EPA). The news of the increase comes just months after the U.S. government announced plans to cut net greenhouse gas emissions by 26 percent below the 2005 levels.

In 2013, total greenhouse gas emissions were 6,673 million metric tons -- an increase of nearly 128 million metric tons of carbon dioxide equivalent over 2012. The carbon dioxide equivalent is a measure of the global warming potential of any greenhouse gas by using warming caused by carbon dioxide as a reference.

ghg emissions1 U.S. Greenhouse Gas Emissions (1990-2013). Photo: U.S. EPA's Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990–2013

According to the EPA’s annual greenhouse gas emissions inventory, this increase can be attributed to an increase in coal consumed to generate electricity -- accompanied by a decrease in natural gas consumption -- and a rise in emissions by vehicles on roads. 

“Over the past few years, we’ve seen increased economic growth and coal has become a bit more competitive with natural gas [which has lower CO2 emissions] over the past year or two,” Michael Mann, a climatologist at Pennsylvania State University, told Climate Central.

Moreover, harsher winters “led to an increase in fuels for the residential and commercial sectors for heating,” the report said. “In 2013 there also was an increase in industrial production across multiple sectors resulting in increases in industrial sector emissions.”

While the winters of 2013 were one of the coldest on record in parts of the Midwest, several other states along the West Coast experienced record warm winters in the same time period -- an extreme weather pattern that continued well into the 2014-15 winters.

In 2013, power plants for electricity generation accounted for 31 percent of total emissions, followed by transportation at 27 percent, and industrial and manufacturing activity at 21 percent.

ghg emissions U.S. greenhouse gas emissions by economic sector, 1990-2013. Photo: U.S. EPA's Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990–2013

However, despite the rise in emissions over the previous year, emissions in 2013 remained way below the peaks of 2007, when net greenhouse gas emissions touched 7,400 million metric tons and carbon dioxide emissions alone crossed 6,000 million metric tons. The greenhouse gas emissions in 2013 were also 9 percent below 2005 levels.