Carbon dioxide emissions from energy consumption by source Data in million metric tons NG STAFFSOURCE: MONTHLY ENERGY REVIEW, U.S. ENERGY INFORMATION ADMINISTRATION

U.S. emissions of heat-trapping carbon dioxide are rising again, posing a potential challenge to President Barack Obama’s climate pledge.

In 2014, energy-related carbon emissions increased for the second consecutive year, although by a smaller amount than in 2013, according to a report Monday by the U.S. Energy Information Administration or EIA.

The uptick, after a few years of decline, suggests the United States could have a difficult time meeting its emissions target. Last month, ahead of historic climate talks in Paris, Obama pledged to reduce total U.S. greenhouse gas emissions by 26 to 28 percent, from 2005 levels, by 2025. The bulk (80 percent) of that total is energy-related carbon emissions, the remainder coming from other gases such as methane.

View Images A coal train stops near White Bluff power plant near Redfield, Arkansas, on June 2, 3014. President Barack Obama has proposed rules to slash carbon emissions from power plants. Photograph by Danny Johnston, AP

The cornerstone of Obama’s climate plan—proposed rules to slash emissions from power plants by shifting away from coal-fired facilities—faces stiff Republican opposition on Capitol Hill. Unless his plan takes effect, the Energy Department’s EIA projects U.S. carbon emissions will continue to rise slightly in the next two years.

Emissions are rising largely because of recent economic growth. In four of the five years from 2008 through 2012, they fell as the Great Recession prompted businesses to shrink and people to drive less. In contrast, emissions rose 2.5 percent in 2013 when gross domestic product, or GDP, expanded 2.2 percent.

Emissions are also up because coal’s decline has slowed. After several years of steep drops, coal consumption jumped in 2013 and barely dipped in 2014. This fluctuation affects emissions because coal produces twice as much carbon dioxide as natural gas when burned.

The EIA sees positive signs, however, in last year’s data. While GDP grew 2.4 percent in 2014, carbon emissions rose only 0.7 percent, suggesting that efforts to reduce air pollution may not necessarily hamper economic growth.

“We were able to offset most of that economic growth,” says Perry Lindstrom, author of the EIA’s emissions report. He says this occurred because of energy efficiency efforts and shifts to cleaner sources such as natural gas. He notes declines or improvements last year in both U.S. energy intensity (energy consumed per unit of GDP) and carbon intensity (emissions per unit of energy consumed.)

What happens in the future, his report says, “will depend largely on a mix of weather, energy sources and economic factors—as well as potential changes in national and state policies.”