By Sharon Kelly
Over the past few years, natural gas has become the primary fuel that America uses to generate electricity, displacing the long-time king of fossil fuels, coal. In 2019, more than a third of America’s electrical supply will come from natural gas, with coal falling to a second-ranked 28 percent, the Energy Information Administration predicted this month, marking the growing ascendancy of gas in the American power market.
But new peer-reviewed research adds to the growing evidence that the shift from coal to gas isn’t necessarily good news for the climate.
A team led by scientists at NASA‘s Jet Propulsion Laboratory confirmed that the oil and gas industry is responsible for the largest share of the world’s rising methane emissions, which are a major factor in climate change — and in the process the researchers resolved one of the mysteries that has plagued climate scientists over the past several years.
That mystery? Since 2006, methane emissions have been rising by about 25 teragrams (a unit of weight so large that NASAnotes you’d need over 200,000 elephants to equal one teragram) every year. But when different researchers sought to pinpoint the sources of that methane, they ran into a problem.
If you added the growing amounts of methane pollution from oil and gas to the rising amount of methane measured from other sources, like microbes in wetlands and marshes, the totals came out too high — exceeding the levels actually measured in the atmosphere. The numbers didn’t add up.
It turns out, there was a third factor at play, one whose role was underestimated, NASA‘s new paper concludes, after reviewing satellite data, ground-level measurements, and chemical analyses of the emissions from different sources.
A drop in the acreage burned in fires worldwide between 2006 and 2014 meant that methane from those fires went down far more than scientists had realized. Fire-related methane pollution dropped twice as much as previously believed, the new paper, published in the journal Nature Communications, reports.
Using this data, “the team showed that about 17 teragrams per year of the increase is due to fossil fuels, another 12 is from wetlands or rice farming, while fires are decreasing by about 4 teragrams per year,” NASA said in a January 2 press release. “The three numbers combine to 25 teragrams a year — the same as the observed increase.”
“A fun thing about this study was combining all this different evidence to piece this puzzle together,” lead scientist John Worden of NASA‘s Jet Propulsion Laboratory in Pasadena, California said in a statement.