Brad Plumer passes along the news that after modest declines over the past few years, US carbon emissions rose in 2013:
The big story here, as usual, involves coal and natural gas....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....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.
It's worth pointing out that the Great Recession played a role too. Both automobile use and general energy consumption declined during the weak economy of 2008-11, but as the economy has started to recover these trends were always bound to reverse. The chart on the right, for example, shows total vehicle miles driven over the past decade or so. This number is very seasonally dependent (more driving in the summer, less in winter), so just take a look at the summer peaks. They increased steadily until 2008, and then dropped, hovering about 3-4 percent below the previous record for the next four years. Then they started to pick up again. At the current rate, we should expect the 2014 peak to be roughly the same as it was in 2007.
Now, it's still good news that it hasn't increased more. After all, US population has increased about 4 percent since 2007, so per capita miles driven is still well below 2007 levels. Still, it's always been the case that our reduction in carbon emissions has been only partly the result of greater efficiencies and the switch to natural gas. It's also been the result of a weak economy. Now, with the economy starting to recover, we're going to have work harder to lock in real gains.