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US Gas Production Revives Atmospheric Ethane After Decades of Decline

Smog is making a comeback.

Despite being pitched by alt-health sketchballs and manufacturers of "air purifiers," ozone is bad for you. It's smog, basically, and it damages your lungs. It also damages plant life. Ozone in the upper-atmosphere is necessary for blocking the Sun's ultraviolet rays, but at ground level, it's among the most widespread air pollutants. Fortunately, since peaking around 1984, ozone levels have been declining.

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This trend, however, is vulnerable. There are many interrelated and unassured factors that regulate or promote ozone concentrations at ground level, including warm temperatures, sunlight, and the presence of precursor gases, like ethane. According to a paper published Monday in Nature Geoscience, ethane emissions, after decreasing dramatically from 14.3 to 11.3 terragrams per year between 1984 and 2010, are again on the rise. The culprit: the US fossil fuel boom.

The findings come courtesy of Detlev Helmig and researchers at the University of Colorado. They're primarily based on 10 years' worth of weekly and biweekly measurements of ethane and propane concentrations at 44 remote stations that are part of the NOAA's Global Greenhouse Gas Reference Network.

Since 2009, ethane concentrations in the northern hemisphere have been increasing by 2.9 to 4.7 percent annually. The NOAA Reference Network data was further supported by ground-based measurements of tropospheric free ethane made at Jungfraujoch, Switzerland, an atmospheric research station situated on an 11,000 foot ridge in the Bernese Alps. The Jungfraujoch measurements, which provide a good representation of the overall continental ethane background concentration, found increases of 4.2 percent per year following a slight pre-2009 dip. No similar reversal was found in similar measurements taken in New Zealand.

As for determining where exactly all of this bonus ethane is coming from, Helmig and co. turned to the pollutant's sibling, propane. Both commonly come from the same sources, but propane differs in that it's relatively short-lived in the atmosphere. As such, it's detected only within close proximity to its source, whereas ethane could have come from anywhere.

Propane concentrations have mostly increased only in the US and downwind areas, according to the Helmig. Meanwhile, central Europe, the Pacific region and the southern hemisphere all remained more or less stable during the same time period. A notable exception was Tiksi, Russia, which had some of the highest propane concentrations anywhere.

Tying the new ethane excesses to US oil and gas production is initially just a matter of matching timelines. Ethane jumped in tandem with the oil boom. Easy enough. But Helmig and his team went further than that.

"To evaluate how this production increase is affecting ethane emissions, continuous airborne measurements of ethane were made over the North Dakota portion of the Bakken shale formation in spring 2014," explain the Finnish meteorologists Hannele Hakola and Heidi Hellén in an accompanying Nature commentary. "If the emissions measured during the airborne study are representative, the formation is responsible for emissions on the order of 0.23 ± 0.07 terragrams of ethane per year, equivalent to 1–3 percent of all ethane emissions globally."

It's not a good look. Smog is among the OG environmental concerns and its reduction has been hard and long fought. As the Finns note, reducing North American air pollution is an important success story. And, now, thanks to the whims of the global energy market, we stand to piss it all away.