Near the quiet Los Angeles neighborhood of Porter Ranch, a natural gas well has spewed at least 78,000 metric tons of methane into the air since October, leading to Wednesday's decision by California Gov. Jerry Brown to declare a state of emergency.
The Environmental Defense Fund called it "one of the largest U.S. natural gas leaks ever recorded." Thousands of families have been forced to move from their homes, with some people complaining of headaches and nosebleeds.
The Southern California Gas Company, which runs the leaking Aliso Canyon Underground Storage Facility, has tried plugging the well with various mixtures, but none of it has stopped the flow of methane. Now the company is drilling several relief wells, a process that could take until February or March to complete.
It's a massive leak — but it's not the only time methane, the main component of natural gas, has found its way into the atmosphere. In 2014, the most recent year for which the Environmental Protection Agency has statistics, around 73 million metric tons of methane were emitted by the petroleum and natural gas industry.
Because it traps heat so well, methane's impact on climate change is 25 times greater than carbon dioxide, according to the EPA. Its effects are shorter-lasting, however, as methane disappears from the atmosphere in about 12 years, compared to up to 200 years for CO2.
Much of that leakage is preventable, and everyone from Google to gas companies to federal regulators are hoping technology can help reduce the amount of methane released into the air.
Where is methane leaking?
Most U.S. methane emissions (29 percent) come from the production, processing, storage and distribution of natural gas, according to the EPA, followed by agriculture (26 percent) and landfills (18 percent).
Of the methane associated with the U.S. natural gas industry, half is leaked in the process of getting it out of the ground and processing it, while the other half is released when it's stored and distributed.
In the best-case scenario, an oil field leaks less than 2 percent of its methane, according to Russ Schnell of the National Oceanic and Atmospheric Administration (NOAA). The worst fields can leak up to 10 percent.
A leak-free facility? That is pretty much impossible, Schnell said. Some fields might have 20 companies operating on 500 square miles, each with facilities filled with pipes and gaskets and valves where methane might escape.
"In an oil field, you might have a million connections," Schnell told NBC News. "Not a hundred, not a thousand — a million. That's a big number."
If 1 percent of those connections were faulty, there would be 10,000 connections leaking methane. And it doesn't escape gently.
"It's not just sitting there," Schnell said. "It's under hundreds of pounds of pressure — in some places much more — so all it takes is a little leak, and out it comes."
Eventually, extracted natural gas makes its way through distribution centers and pipelines to cities, where it also escapes into the atmosphere. A Stanford study from September found 3,400 natural-gas pipeline leaks in Boston and 5,900 in Washington, D.C., which equates to roughly 4.3 leaks per mile.
Aging infrastructure in cities is not only bad for climate change, it can sometimes lead to disasters, like the 2014 explosion in Harlem that killed seven people.
How to stop the leaks
Methane is flammable, causes headaches and dizziness and warms the Earth. It's also very hard to detect.
"You can't see it, you can't smell, you can't hear it," Schnell said. "It's almost an invisible leak."
It's hard to grasp how bad the leak at the Aliso Canyon Gas Storage Field is without looking at the infrared aerial footage taken by the Environmental Defense Fund.
It's not yet clear exactly why the leak started or where it occurred in the damaged well. A class action lawsuit filed in Los Angeles Superior Court in December claimed that the Southern California Gas Company (a division of Sempra Energy in San Diego) failed to replace a safety valve 8,500 feet below the surface in 1979.
In response, a company spokesperson told NBC News that it's true that the well "does not have a subsurface safety valve" but that regulations from California's Division of Oil, Gas and Geothermal Resources "do not require that these types of valves be installed in wells" such as the one outside Porter Ranch.
"A new safety valve would have almost certainly reduced or eliminated the severity of the gas leak," Rob Jackson, an environmental science professor at Stanford, told NBC News.
Old, corroded pipes and valves are a huge problem, but there are no space-age materials out there to replace them; they simply need to replaced. What is really needed, Jackson said, is careful monitoring, paired with quick action from gas companies.
Simply flying a plane equipped with an infrared camera over a facility once a month should be enough to give an accurate picture of how much methane it's leaking, according to Schnell.
Gas companies have an incentive not to waste natural gas — mainly, leaked gas is wasted money. But with oil prices so low, Jackson and Schnell said, many natural gas companies are scrambling to remain profitable, let alone invest in new infrastructure to monitor leakage.
That is where third parties come in. In 2014, Jackson and his team drove along natural gas pipelines in a car equipped with a laser spectrometer (paired with GPS and a sensor to measure wind speed and direction) to map where methane was leaking in several cities. Google Earth Outreach and the Environmental Defense Fund did something similar with Google's Street View cars.
Methane detection on the ground can be complemented by air power. NASA's Jet Propulsion Laboratory is working with Pacific Gas & Electric to mount methane sensors on drones. And, of course, there are planes and helicopters that can be outfitted with infrared cameras.
An increased number of fixed sensors in methane facilities could also help prevent leakage, Schnell said. Over the summer, the EPA proposed new regulations that would require "optical gas imaging" technology to be used at natural gas well sites to look for leaks.
There are quite a few companies — inicluding FLIR, who recently debuted a $600 thermal camera at the Consumer Electronics Show in Las Vegas — that make this kind of equipment.
The Southern California Gas Company doesn't have sensors to constantly monitor for methane leakage. Instead, a company spokesperson told NBC News, "in the storage field, we conduct daily observations to ensure everything is in proper working order and weekly checks of pressure readings to confirm their condition." The company also makes annual inspections using a leak-detection tool, the spokesperson said.
The leak was discovered on October 23 because an employee investigated an "odor report," according to the company. The Southern California Gas Company, like many other firms, adds the chemical mercaptan to gas to give it that recognizable rotten egg smell.
"If the leak had been going on since before October 23, it would have been detected both by SoCalGas employees on site, who do twice-daily patrols, as well as people in the neighboring community," a company spokesperson said.
Large accidents like the one in Porter Ranch are rare. Most of the methane released from the oil and gas industry comes from less dramatic leaks stemming from a few high-emitting facilities, Jackson said.
Those aren't state-of-emergency incidents, but rather consistent, easily preventable breakdowns in maintenance and monitoring. Third parties could be key in making sure they are spotted before they do too much damage.
"My experience is that companies care deeply about the safety and integrity of their networks," he told NBC News. "We all do better when we are being watched, though."