A current scientific challenge today is the accurate quantification of total methane emissions in the US. This can serve as an important baseline against which to compare how emissions change with the burgeoning of the fracking industry. It also gives a sense of the role of methane in global warming- it has 30 times the warming potential of CO2 if released into the atmosphere before being combusted for fuel.
A new paper in Geophysical Letters has now used a new space-based observation method to quantify average methane emissions across the US from 2003-2009. Of particular interest is a concentrated region of methane emissions found in the Four Corners area, a location not previously expected to show such large emissions.Here are a couple maps showing the main results. The left image is from SCIAMACHY, a European satellite speeding about in orbit around the Earth that gathers data of emitted and reflected light from the Earth’s surface and atmosphere. Every molecule in the universe absorbs and re-emits light at a specific wavelength, based on the types of bonds that make up the molecule and their vibrational frequencies, so the satellite can spatially pick out different emissions from regions around the globe (the specifics are much more complicated than that, but that’s the gist!).
So here they plot intensities of emissions related to methane (CH4) molecules. You can see a large red spot in the southwest US, right at the Four Corners region. Nobody ever knew this area emitted so much methane! This is clear from the right graph, which shows previous land-based estimates of methane emissions based on inventories, I believe related to natural gas and oil production. You can see all the hotspots in the northeast there, but much smaller regions of intensity in the West.
This is crucial information because it indicates we need multiple methods of quantifying our methane emissions – land-based inventories may be underestimating the actual rates. So you may be thinking – have they been increasing fracking operations in the Four Corners region? Is that to blame? Indeed, this regions is ripe for fracking operations, and their preparation is underway. But this strong emissions signal has been steady across 7 years, from 2003-2009, with no seasonal or interannual variations. And there was no fracking in 2003! So something else is the culprit…
It turns out that, instead of fracking, there are plenty of coal mining operations in the Four Corners region. And there also happens to be a rich source of coalbed methane, methane gas that sits inside all the crevices and gaps of the coal in the mine (see figure above). Coalbed methane has long been known to be dangerous to miners and their canaries, but this is some of the first data to show its emission potential can compete with other methane sources. So mining operations in this region are largely to blame, likely due to unforeseen or unknown leaks from the mine.
This paper demonstrates a key role for new satellite technology to provide a second measurement of global methane (or other) emissions to confirm or illuminate beyond ground-based inventories. More data about coalbed methane emissions from mines will be important to see if this type of leakage is universal and if there are simple solutions to stop it. The authors also indicate that, since fracking is on the rise in this region, these data provide an important baseline for comparison. Otherwise, this hotspot may have been wrongly attributed!
Kort, E., Frankenberg, C., Costigan, K., Lindenmaier, R., Dubey, M., & Wunch, D. (2014). Four corners: The largest US methane anomaly viewed from space Geophysical Research Letters DOI: 10.1002/2014GL061503