Despite reports of air quality dipping to dangerous levels in Los Angeles this week, a pair of studies from NASA found that one type of emission has been successfully reduced across the region in recent years.
Two contrasting studies sought out to determine whether or not levels of methane, one of the primary greenhouse gases associated with global climate change, lowered in Los Angeles over the past several years.
While taking different approaches, both studies found that human-caused methane emission has gone down.
The first study was published in February in Environmental Research Letters. Scientists looked at sensors across Los Angeles, Orange, San Bernardino and Riverside counties and found that methane emissions were reduced by 33 million pounds, or about 7%, per year.
The scientists evaluated data from ground-based sensors placed around the region as part of the “Megacities Carbon Project,” a globe-spanning initiative to monitor greenhouse gases in major metropoli like Los Angeles, Indianapolis and Washington D.C.
The large swath of sensors measure emissions from Malibu to the Inland Empire and down through Orange County. They’ve been gathering data since 2015 and have showed steady month-to-month decreases, which indicated that emissions were successfully being reduced. One of the regions responsible for a large drop-off was the area between Granada Hills and Ontario.
Although the study doesn’t explicitly state the reason for the reductions, lead author Vineet Yadav theorized that better management of natural gas pipelines and equipment in the area, as well as improved infrastructure at a waste site near Granada Hills likely played a role in reducing methane releases.
A second study, which was published in March in Environmental Research Communications, focused on oil refineries in L.A.’s South Bay. Researchers used data that was gathered by a NASA instrument mounted on the bottom of an aircraft.
From 2016 to 2017, the instrument was used during flights that covered more than 22,000 square miles as part of the California Methane Survey. The flights identified 48 methane “plumes” coming from several local refineries.
Three years later, much of that flight path was flown again, and researchers discovered that most of those previously identified sources appeared to have stopped emitting the greenhouse gas entirely, with only 11 plumes identified.
In total, researchers identified a 73% reduction in methane released, which equated to about 2,639 pounds of methane per hour being removed from the air.
There was also a significant drop in emissions from oilfields in the Central Valley during that time frame.
Researchers did stress that much of those reductions could be linked, in part, to a decrease in oil production due to reduced demand caused by the COVID-19 pandemic.
Andrew Thorpe, lead researcher of the second study, said improved equipment maintenance and successful mitigation efforts between 2016 and 2020 may have contributed as well.
While both studies were unable to definitively answer why or how methane emissions declined in recent years, researchers say that being able to effectively detect and measure emission levels is a critical step in finding ways to reduce greenhouse gas emissions.