An unusual amount of the climate change-causing gas methane has been detected over the Southwest United States,
Researchers mapped satellite data to look at the largest methane cloud seen from space in the U.S., the University of Michigan reported. The team found that than half a teragram per year in methane was coming from Four Corners region, where Arizona, New Mexico, Colorado and Utah meet. This region gave off about as much methane as all of the coal, oil, and gas industries in the United Kingdom.
"There's so much coalbed methane in the Four Corners area, it doesn't need to be that crazy of a leak rate to produce the emissions that we see. A lot of the infrastructure is likely contributing," said Eric Kort, assistant professor of atmospheric, oceanic and space sciences at the U-M College of Engineering.
Coalbed methane is a variety of the gas stuck to the surface of coal, and has been extremely hazardous to miners in the past.
"We see this large signal and it's persistent since 2003," Kort said. "That's a pre- fracking timeframe in this region. While fracking has become a focal point in conversations about methane emissions, it certainly appears from this and other studies that in the U.S., fossil fuel extraction activities across the board likely emit higher than inventory estimates."
The researchers warned the Four Corners may not even be the highest emitting region just because it harbors the large distinctive gas cloud. Other huge methane producers could be convoluted by nearby sources.
This new study introduces a new technique for finding methane leaks using a satellite instrument, dubbed the European Space Agency's SCIAMACHY, to determine methane measurements over a specific area. The team discovered the high concentrations of methane over the Four Corners region by zooming in on this region and using a mathematical model to control for wind.
"We didn't know this was a region we should look at. We found it from space," Kort said. "We've demonstrated that satellite measurements can help identify, locate and quantify anomalous methane emissions in regions that are unexpected."
Methane can come from both natural and man-made source; the natural gas has 30 times the short-term short-term heat-trapping effects of carbon dioxide. Reducing methane in the atmosphere is believed to be an effective method of curbing global warming.
The findings were published in a recent edition of the journal Geophysical Research Letters.
