The United States has been one of the few bright spots for climate-change policy in recent years. Thanks to the recession, improved efficiency measures and the shale-gas boom, the nation's carbon-dioxide emissions from energy fell 12 percent between 2005 and 2012.

But the party's now officially ending, at least for those worried about global warming. In an early estimate, the U.S. Energy Information Administration says that U.S. carbon-dioxide emissions from energy sources increased 2 percent in 2013:



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.

Further reading:

-- 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.