Searching for methane leaks, scientists find “ultra emitters”

The fossil fuel industry is releasing millions of metric tons of methane gas in giant plumes during extraction and transportation of those fuels—at high costs for the climate, society, and even the industry’s pocketbooks.

Although methane emissions are relatively low compared to CO₂ emissions, each ton has a whopping 30 to 80 times the relative warming potential (depending on the timescale of interest). On the plus side, methane has a much shorter atmospheric lifetime—roughly nine years. So reining in emissions as soon as possible represents one of the better bets for lowering temperatures in the coming decades.

But to date, methods for detecting methane emissions have been limited, and it has been challenging to find, measure, and curtail all anthropogenic sources. A recent study describes how researchers used a European Union satellite to carry out a global survey of unusually large methane plumes, finding 1,800 “ultra-emitters” during the time frame of 2019 to 2020. Two-thirds of these emitters were connected to the oil and gas industry, and just three countries—including the US—were responsible for the majority of the problem.

Eliminating these leaks could prevent about 0.005° C of warming over the next 10 to 30 years, potentially saving society billions of dollars in climate-related costs. Many such leaks are due to avoidable issues like maintenance practices and equipment failures—a particularly egregious way to heat up the planet.

Tracking methane

Past research has shown that at least a third of anthropogenic methane comes from the fossil fuel industry. However, due to the lack of required reporting for unintentional—or even intentional (during routine maintenance)—methane leaks, this figure largely underestimates actual emissions.

“I'm glad that we’re starting to reconcile the atmospheric data sets and what we report because we cannot continue to be blind and then use numbers that we know are completely underestimating the truth,” said lead author Dr. Thomas Lauvaux. “It's really hard to imagine that some policymakers are working with numbers that are completely bogus.”

Although these leaks account for only 8–12 percent of the industry’s total methane emissions, every opportunity to save even a fraction of a degree of warming is still important for reaching climate targets. But these leaks are hard to track, and weeks-long plane surveys—such as those used to monitor methane emissions from Californian landfills—won’t work for global emissions.

As a result, researchers have turned to tools such as the European Space Agency’s Sentinel 5-P satellite and the onboard TROPOspheric Monitoring Instrument (TROPOMI). Using data collected by these instruments, the team systematically searched for methane releases of more than 25 tons per hour. Critically, the monitoring provided daily “snapshots” that allowed the researchers to estimate how much total methane was being lost during these events.

“Initially, we were quite disappointed because we discovered that the sensitivity of our system was pretty low (>25 tons/hour), but then we couldn't believe how many of these giant blooms we discovered,” said Lauvaux. “If you don't have a satellite covering the world every day, you might not see many of them, and that's how they've been able to avoid the documentation—because we didn't have this global matrix solution before.”

The data set also picked up ultra-emitters from coal, agriculture, and waste management (33 percent of total detections), but the majority came from oil and gas production or transmission facilities. Unsurprisingly, these were mostly in some of the largest fossil fuel basins around the world: Turkmenistan, Russia, the United States, Iran, Kazakhstan, and Algeria.

In total, these leaks released 8 million metric tons of methane per year. Of this, Turkmenistan and Russia were responsible for close to 1 million metric tons per year each, while the US ranked third, with a little under 0.5 million metric tons per year.