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Methane Is Leaking All Over The Place

It’s now been 103 days since workers from the Southern California Gas Company discovered a natural gas leak coming from the Aliso Canyon underground storage field near the Porter Ranch neighborhood of Los Angeles. In late November, 58,000 kilograms of methane per hour were leaking into the atmosphere.annual methane emissions from the entire U.S. natural gas supply chain works out to about 706,200 kilograms of methane per hour, according to calculations that Colorado State University engineer Anthony Marchese did for CarbonBrief.

">1 As of Jan. 21, that number was down to 20,000 kilograms per hour, but overall the leak has released more than 91,000 metric tons of methane — emissions equivalent to burning more than 862 million gallons of gasoline.

The leak, SoCalGas says, will finally be stopped by late this month. The methane, though, will linger in the atmosphere.

Although California health officials have determined that the leak poses minimal health risks, its danger to the climate is more severe. About 10 percent of U.S. greenhouse gas emissions came from methane in 2012, and 30 percent of those emissions came not from fuel use, but from the extraction and distribution of oil and natural gas. Methane sticks around in the atmosphere for decades, rather than centuries like carbon dioxide, but it absorbs much more heat. On a time scale of 20 years, methane’s effects on global warming are about 84 times more potent than carbon dioxide’s.its effects are greatest on a short time scale. Over 100 years, it’s 34 times more potent than carbon dioxide, according to the Intergovernmental Panel on Climate Change.


Methane is the primary component of natural gas, and it can leak almost anywhere in the natural gas supply chain. Studies show that it is leaking at almost every point in the supply chain — at drilling sites, along pipelines, at compression stations, at storage facilities like Aliso Canyon and along the networks of piping that deliver natural gas to homes. About the only thing unusual about the Aliso Canyon leak is its size.

Now if we could only figure out how much methane is leaking worldwide.

The gas leak problem is hard to quantify, because there’s no unified system to find and measure these leaks. A study published in the journal Science in 2014 found that official inventories routinely underestimate methane emissions from leakages. And recent studies that have taken measurements also suggest that the problem is widespread.

The city of Boston alone had at least 1,868 documented unrepaired leaks in its gas lines as of March 2015, and the oldest has been leaking since 1985.4 As large as that number may sound, it underrepresents the problem because it includes only known leaks that have been reported to gas companies, said Audrey Schulman, president of the Home Energy Efficiency Team, a nonprofit group in Cambridge, Massachusetts, that focuses on energy efficiency issues and collected data on Boston and other Massachusetts cities.


Leaks like these can be fixed, but utilities have little incentive to do so, especially if it requires tearing up roads or sidewalks. Proposed legislation in Massachusetts would require gas companies to look for and repair leaks whenever major road work is underway.

That you, me and our neighbors rarely smell the gas also leads to dithering. Unlike spills in oil pipelines, methane leaks can go undetected for days, weeks or even longer because the gas is invisible and odorless. To make leaks easier to detect, natural gas that’s headed to homes (as the gas stored at the Aliso Canyon facility was) has odorants added to give it a rotten-egg smell. That works well when the leak is in your house or another contained space, but when it’s streaming into the air outside, it may escape notice.

The good news is that methane watchdogs are developing new ways of finding the stuff. GPS-enabled devices installed on cars to measure methane in the air are making it easier to find and measure leaks. “It’s basically like Google Street View, except for methane,” said Nathan Phillips, a researcher at Boston University who has used this technique to map methane leaks in cities. “These are not blobs sloshing over the city; they’re very spatially resolved slots,” Phillips said, referring to the distinct columns of gas you can see on methane maps. Driving 785 miles in the city of Boston, Phillips and his team identified 3,356 leaks. In Washington, D.C., his group drove 1,500 miles of road and found 5,893 natural gas leaks. Another research group found “hundreds to thousands” of likely leaks in Manhattan in New York City using street measurements.


The Environmental Defense Fund, Colorado State University and several utility companies have partnered with Google to do similar work, using Google Street View cars to map methane leaks in cities. In Boston and in Staten Island, New York, these cars found an average of one leak for every mile that they drove.

Methane is making its way to the atmosphere outside our cities, too. Figures from 2007 showed that there are about 400 underground methane storage sites like Aliso Canyon in the U.S., and these storage facilities “seem to have fallen through the cracks in terms of regulation,” Phillips said. There’s little federal oversight of such facilities, and state oversight is variable and spotty.

Gas producers are purposefully putting it into the air, as well. During the natural gas production cycle, methane is often flared, or burned off as waste. Such flaring is primarily done in oil production areas where gas isn’t the main product, and often there isn’t infrastructure in place to get the gas to market or use it locally. With no easy way to capture and transport it, standard industry practice is to burn it off. A global survey published in December identified 7,467 natural gas flare sites in 2012. Every flare pushes more greenhouse gases into the atmosphere, as well as combustion byproducts such as black carbon that can also contribute to climate change.

Most of this flaring — 90 percent — takes place at production sites, said Christopher Elvidge, the study’s lead author and a physical scientist at the National Oceanic and Atmospheric Administration’s Earth Observation Group in Boulder, Colorado. Elvidge and his colleagues estimated that in 2012 these flares burned 143 billion cubic meters of gas. The volume of gas flared represents 3.5 percent of global natural gas consumption and 19.8 percent of U.S. natural gas consumption: enough gas to power 74 million automobiles driving 13,476 miles per year. And those are emissions that add to global warming without giving us any energy in return.

This map from Elvidge’s paper shows the spatial distribution of natural gas flaring his group found in 2012.


“The technology to make use of the gas is available; the question is, do they want to invest in a solution to stop their gas flaring, or keep doing what they’ve been doing?” Elvidge said.

Across the gas production and distribution cycle, a minority of sites are responsible for a disproportionate amount of emissions. When Phillips’s team revisited some of the leaks it found to measure the amount of gas they were emitting, the researchers discovered that approximately 15 percent of leaks accounted for about 50 percent of the lost gas. And that means strategically targeting relatively few leaks could provide a cost-effective solution.

The same issue exists at production sites. “We have data now,” said Steven Hamburg, chief scientist at the Environmental Defense Fund. “Roughly one-third of production sites have very low leakage, and that’s good news. So how do we get the other sites to have profiles like that?” The problem generally isn’t a lack of technologies for stopping or capturing leaks, it’s that those technologies aren’t being used where they’re needed most.

That could soon change. In January, the Obama administration announced that it is taking steps to regulate and reduce methane emissions related to oil and gas production. The new rules would require oil and gas companies to capture gas that leaks from their sites in the U.S. It’s part of the administration’s goal of cutting the oil and gas sector’s methane emissions by 40 percent to 45 percent from 2012 levels by 2025.

Cutting methane alone won’t stop long-term warming (to do that, you need to cut CO2 emissions too), but reducing methane emissions could do a lot to reduce the rate of warming in the short term. In light of last year’s record-setting temperatures, that’s an appealing prospect.

CORRECTION (Feb. 3, 12:22 p.m.): An earlier version of this article incorrectly described the role of utilities in looking for methane leaks. Federal and state standards require utilities to look for leaks; it is not the case that utilities are generally not required to look for them.

CORRECTION (Feb. 3, 9:22 p.m.): An earlier version of this article misstated how many gallons of gasoline were equivalent to the methane emissions leaking from the Aliso Canyon storage field. It is equivalent to 862 million gallons of gasoline, not 862,000.


  1. For context, annual methane emissions from the entire U.S. natural gas supply chain works out to about 706,200 kilograms of methane per hour, according to calculations that Colorado State University engineer Anthony Marchese did for CarbonBrief.

  2. Methane’s global warming potential compared with carbon dioxide is different depending on what time frame you use to make the calculation. Because methane is shorter-lived than CO2, its effects are greatest on a short time scale. Over 100 years, it’s 34 times more potent than carbon dioxide, according to the Intergovernmental Panel on Climate Change.

  3. The video below is courtesy of Boston University professor Nathan Phillips, Bob Ackley of Gas Safety Inc. and

  4. The Home Energy Efficiency Team (HEET) web page linked here gives the city’s number of unrepaired leaks as 1,853 in March 2015, rather than 1,868. The totals are different because different methods were used to determine whether multiple reports from a given area referred to the same leak.

Christie Aschwanden was a lead science writer for FiveThirtyEight. Her book “Good to Go: What the Athlete in All of Us Can Learn from the Strange Science of Recovery” is available here.