Hold Your Rejoicing About Those Falling CO2 Emissions

By Michael D. Lemonick

Remember global warming? You know, that worldwide disaster we were all so worried about way back in 2011? It wasn’t an unreasonable fear, of course: the world has been pumping greenhouse gases (especially carbon dioxide, or CO2) into the atmosphere like there was no tomorrow. Greenhouse gases trap heat. Ergo, said both the theory and the evidence, global temperatures are heading upward, forcing ice to melt, sea level to rise, and extreme weather to come along more often.

But all of that is so last year. The Associated Press is reporting  a “surprise turnaround” in carbon-dioxide emissions. Based on a document from the federal Energy Information Agency, the AP points that CO2 emissions have fallen to their lowest level in 20 years — and it’s not because of any new government regulations, but rather because natural gas has replaced coal in many power plants. Gas emits much less CO2 than coal, and thanks to fracking, gas has become extraordinarily cheap and plentiful. Problem solved! Or at least as the headline more responsibly puts it, “some experts optimistic on global warming.”

Natural gas pipeline. 

Really? These experts might want to think again. It’s true that natural gas emits about half as much CO2 as coal in producing a comparable amount of energy, but half as much isn’t zero, and zero, or as close to it as is humanly possible, is where the world needs to get in a big hurry.

The reason: a large fraction of the carbon dioxide we put into the atmosphere is going to stay there for thousands of years. Even if we were to cut off emissions completely right this minute (an obviously impossible and absurd notion) atmospheric CO2 levels would drop excruciatingly slowly, and they’d be trapping extra heat all the while. The only way to avoid permanent and dramatic changes to the climate, argued NASA scientist James Hansen in 2008, would be to limit carbon concentrations to 350 parts per million — or, since we’re already up to about 395 parts per million, to bring them down quickly to that level. (For comparison, the level before we began burning fossil fuels in earnest in the early 1800’s was about 270-290 part per million).

If that’s the case, then natural gas is hardly an answer. As scientists Ken Calderia and Nathan Myhrvold showed in a paper earlier this year, gas can ultimately cut emissions, but during the time you’re building the plants — a process that itself takes substantial energy — you’ve added so much more CO2 to the air that, as Myhrvold told Climate Central, “It’s like living on a credit card. It’s easy to get into a situation where it will take years and years to pay back.” It’s not just the CO2, either: drilling for natural gas releases substantial amounts of methane, which is an even more powerful greenhouse gas than carbon dioxide.

Besides, the boom in cheap natural gas isn’t going to last forever. As the AP story noted, “. . . changes in the marketplace — a boom in the economy, a fall in coal prices, a rise in natural gas — could stall or even reverse the shift. For example, U.S. emissions fell in 2008 and 2009, then rose in 2010 before falling again last year.”

Here’s another sour note: emissions may be on the decline for the moment in the U.S., but they’re still rising worldwide, so the atmosphere’s CO2 burden, with all those hundreds or thousands of years of heating that implies, is still getting larger.

And here’s yet another: the natural gas boom may be depressing the market for truly renewable forms of energy like wind and solar — the kind that put out zero carbon emissions whatever. It’s quite true, as University of Colorado environmental policy expert Roger Pielke, Jr., said in the AP story, that “if you make a cleaner energy source cheaper, you will displace dirtier sources.” But you can clearly also displace even cleaner sources.

To sum up: emissions have dropped in the U.S., thanks to a form of energy that’s ultimately not much cleaner than coal, and which has stalled conversion to truly clean energy. Meanwhile, worldwide emissions are still growing, putting CO2 into the atmosphere as though it were some sort of global Roach Motel where molecules can check in, but they can’t check out.

This may make some experts optimistic. It doesn’t do a lot for me.