Crews work on stopping a gas leak at a relief well at the Aliso Canyon facility above the Porter Ranch area of Los Angeles in December 2015. (Pool photo by Dean Musgrove/Los Angeles Daily News via AP)

The massive Aliso Canyon methane gas leak of late last year was already one for the record books.

Recent research suggests that the Los Angeles-area leak poured 97,100 metric tons of the powerful greenhouse gas into the atmosphere between late October 2015 and February. The study also found that the leak, if translated into automotive tailpipe emissions, would be equivalent to the effect of the yearly greenhouse gas emissions from 572,000 cars.

Now, new research from NASA and its partners has underscored in a different way how big it was: A satellite-based instrument was able to identify and isolate the leak from space, the first time this has ever been accomplished for a single-source emission of methane.

The observations of the plume of gas were first detected by a device called the Hyperion spectrometer, which is carried by NASA’s Earth Observing-1 satellite. The spectrometer measured what the scientists call the “infrared signature” of methane three separate times, and then the observations, and their accuracy, were separately confirmed by NASA aircraft.

The findings were just published in the journal Geophysical Research Letters by NASA’s David Thompson and a team of colleagues with the Jet Propulsion Laboratory, Caltech, the Hemholtz Centre Potsdam in Germany and NASA’s Goddard Space Flight Center.

“For the first time — to our knowledge, anyway — we’ve been able to see the methane plume from space,” Thompson said. “And this is important because it sort of presages the possibility of using other instruments that are focused on methane in order to do similar things on a much wider scale.”

Here’s an image that NASA’s Jet Propulsion Laboratory released to accompany the research:


Comparison of detected methane plumes over Aliso Canyon, California, acquired 11 days apart in Jan. 2016 by: (left) NASA’s AVIRIS instrument on a NASA ER-2 aircraft at 4.1 miles (6.6 kilometers) altitude and (right) by the Hyperion instrument on NASA’s Earth Observing-1 satellite in low-Earth orbit. (NASA-JPL/Caltech/GSFC)

The Hyperion spectrometer is an optical instrument that scans in “many hundreds of wavelengths,” Thompson said, which allows for the identification of specific gases.

“Every gas leaves its fingerprint on the light that passes through it,” he continued. “So what the algorithms we applied do is they examine the imagery from the spacecraft to see the very unique spectral signature of methane, and then map it over wide locations.”

This was possible even though the spacecraft that carries Hyperion is currently drifting in its orbit, having long since run out of fuel, and despite the fact that the spectrometer was not designed to make measurements of methane. All of this meant that the instrument was “severely handicapped,” the researchers write. So future, more strategically tailored methane measurements could be considerably more accurate.

The work comes at a time when remote imaging technologies, more and more, are helping scientists understand the global distribution and major sources of air pollution. Recently, another satellite-based study identified dozens of new, major sources of sulfur pollution around the globe.

Improving methane leak observations will not only allow more precise estimates of how much countries are contributing to the atmospheric greenhouse gas burden — a key goal of the Paris climate agreement — but will help track the hardest hitting gases in particular, such as methane. While it has a far shorter atmospheric lifetime than carbon dioxide, methane causes far more warming than an equivalent amount of CO2 while it lasts, making large releases particularly consequential.

The space-based gas spotting trend will only increase, based upon the new research and further improvements of it. “Future satellite systems that focus on methane could be much more sensitive to an event like this one,” Thompson said.

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