What happened? The big story here, as usual, involves coal and natural gas. Namely, U.S. electric utilities burned a bit more coal and a bit less natural gas in 2013. And, since coal emits more carbon when burned for electricity, that increased emissions:
Energy analysts were predicting coal's rebound back in March, and it all comes down to prices. The shale fracking boom had pushed natural gas prices to unsustainably low levels — down to a dirt-cheap $2 per million BTUs in 2012. As a result, electric utilities have been switching to natural gas as fast as they could since 2006. The chart above shows that nicely.
But prices crept up again this year past $4 per million BTUs, thanks to colder winters, higher demand for heating fuel, scaled-back drilling, and also new storage facilities that are preventing a glut of gas on the market. As a result, some electric utilities found it economical to shift back to coal. That increased emissions.
Now, U.S. energy-related carbon emissions are still 10 percent below 2005 levels. But President Obama has set a goal of 17 percent below 2005 levels by 2020. And the administration has already conceded that the nation likely won't get there without further hard caps on power-plant emissions — something the Environmental Protection Agency is now working on.
Also, as an important asterisk: The EIA is only counting carbon-dioxide emissions from energy sources like coal, natural gas, and oil. This makes up about 84 percent of all of America's greenhouse-gas emissions. But it leaves out other potent, heat-trapping gases like methane, which can leak out of natural gas operations, landfills, and farms. The EPA takes its own detailed inventory of those emissions, but a full assessment of last year won't be out until 2015.
-- Here's a look at how carbon emissions fell in 2012. Natural gas wasn't the only factor; improved efficiency for buildings and vehicles played a big role, too.
-- Here's a more detailed look at the Obama administration's plan to bring emissions down 17 percent by 2020. Note that this is only a first step toward broader international efforts to tackle climate change. It's not sufficient on its own.