This story originally appeared on Undark and is part of the Climate Desk collaboration.
Every week, dozens of metal pistons will arrive at NOAA's Earth System Research Laboratory in Boulder, Colorado, each loaded with air from a distant corner of the world. The research chemist Ed Dlugokencky and his colleagues in the Global Monitoring Division catalog the canisters and then use a series of precision tools, a gas chromatograph, a flame ionization detector, sophisticated software to measure how much carbon dioxide, nitrogen oxide and methane each flask contains.
These air samples were collected at observers in Hawaii, Alaska, American Samoa and Antarctica and from high towers, small airplanes and volunteers on all continents. They have been to Boulder for more than four decades, as part of one of the world's longest running greenhouse gas monitoring programs. The air in the pistons shows that the concentration of methane in the atmosphere has risen steadily since 1
The amount of methane in the atmosphere has increased since then. And no one really knows why. Also, no one saw it coming. The methane levels have climbed more steeply than climate experts expected, to an extent "so unexpectedly that it was not considered in road models that prepared the Paris Agreement", as Dlugokencky and several co-authors noted in a recently published paper.
As the year picks up and the methane pile up, the solution of this mystery has taken on increasing urgency. During a 20-year time frame, methane puts 86 times as much heat in the atmosphere as carbon dioxide. It accounts for about a quarter of the total warming of the atmosphere so far. And while the steady increases in atmospheric carbon dioxide and nitric oxide are deeply disturbing, they are at least consistent with the researchers' expectations. Methane is not. The methane – probably humanity's earliest signature on the climate – is the wild card.
People have been producing methane for thousands of years by clearing land with fires, raising livestock and growing rice. Thanks to air bubbles trapped in Antarctic ice cores, we know that the global average methane concentration in the atmosphere has almost tripled in response. Since it only lasts about a decade in the atmosphere, cutting methane is a relatively fast-acting lever to lower climate change. But it's not clear how to pull that lever.
Researchers continue to offer competing hypotheses to explain the global spread, and there is no shortage of potential suspects. "The really fascinating with methane," says Lori Bruhwiler, a researcher from NOAA, "is the fact that almost everything we humans do has an effect on the methane budget, from producing food to producing fuel to disposing of waste."  "And then, boom, look at how it changes here," says Dlugokencky, pointing to a chart on his computer screen. "This is really a sudden change in global methane budget, starting around 2007."
People are directly responsible for about 60 percent of global methane emissions. It sucks from rotting food waste in landfills, from anaerobic pig manure lagoons, from rice fields and exposed coal seams. Livestock belch it as a by-product of their digestion. It flows out of the large metallic exoskeleton of oil and gas wells, pumping stations, pipelines and refineries that disappear the world.
The balance comes from natural sources – wetlands, rivers and lakes, fires, termites, geological sweeps, thawing permafrost. Wetlands are the largest single source, which contributes about 30 percent of the total methane emissions globally. As it happens, they are also the biggest source of uncertainty about the carbon budget, according to Benjamin Poulter, a NASA researcher and contributor to the Global Carbon Project, an international consortium of researchers publishing one of the most cited estimates of global methane budget. This uncertainty can lead to the debate about what drives the increase as a highly educated guessing game.
"There are so many hypotheses and powerful papers out there over the last two years that cover the full range of explanations why there is this renewed growth," says Poulter.
Thanks to careful measurements by NOAA scientists and others, We know that there are about 1,850 methanol molecules in the atmosphere for every billion air molecules, usually stoned as parts per billion, or ppb-in today's atmosphere, compared to about 700 parts per billion in pre-industrial times, but the processes behind today's numbers are much less visible "It's like knowing the playoffs of a game, but not who did what and how.
Getting answers is not just an academic exercise; it's important to know just what humanity can face when the planet continues to warm." must have process representation to understand these mechanisms, "says Eric Kort, an atmospheric researcher at the University of Michigan", so we can say with Some changes in temperature and hydrological cycle, we expect methane emissions to increase with X amount. "Without that understanding, Card suggests, we can't answer any important questions about what is weighing ahead." Is atmospheric methane as a result of climate change, not our direct emissions? Are some thresholds going over? "
" There is a bad problem, "Short adds," but it is not inseparable. "
A possible convincing explanation needs to answer three questions. What explains the long-term increase in methane levels over the past 40 years? Why was it a break? And why was it so suddenly rising after 2006? Only three parts of the global methane budget is large enough to be credible offenders: microbial emissions (from livestock, agriculture and wetlands), emissions of fossil fuels and the chemical process through which methane is scrubbed from the atmosphere.
The first theory for traction determination Debt for fossil fuels, based on a certain suspected timing: The use of horizontal drilling and hydraulic fracturing – a method for cutting buried hydrocarbons It means blowing deep layers of rock with a cocktail of water, sand and chemicals rising in the US The oil and gas industry is right around the time when atmospheric methane levels shot up, but other researchers are convinced that growing boskapar, producing metangrika belches and manure, are required. Some researchers pore over satellite data to prove that methane production from natural sources, such as wetlands and wildernesses, is changing.
And others still claim that sin is not an excess source at all, but the steady or perhaps very sudden disappearance of a traditional methane "sink". After an average residence time of about a decade, methane is oxidized to carbon dioxide and water vapor by chemical reactions with hydroxyl radicals (OH). However, this atmospheric removal process may be weakened, though possibly because OH levels decrease due to reactions with other anthropogenic contaminants.
Of course, it can be a complex combination of all these factors. Furthermore, the image confuses, some researchers argue that the tip of concentrations is not a spike at all. Rather, they say that the break in growth from 2000 to 2006 is the true anomaly. Through this calculation, what happened in 2007 was a return to a "normal" trend of anthropogenically driven growth, perhaps increased by a decrease in chemical removal of methane. If so, methane continues to accumulate, like the water in a bath with an open faucet and a plugged drain.
These ongoing scientific disputes reveal the problem in the heart of the methane mystery: Several narratives can be neatly tailored to the available evidence. "Really good observations can be interpreted in ways that seem contradictory," says Kort. To sort through everything, scientists must balance the information provided by different categories of clues.
Top estimates are based on observations using sensors on towers, aircraft or satellites and models that respond to downward transport of emissions from sources and chemical reactions with other components of the atmosphere. Bottom-up methods involve measuring emissions near the source (a gas well, landfill, even a cow's intestine) and extrapolating from them to estimate wider-scale emissions.
Trace elements also offer important clues. Carbon monoxide is emitted with methane from fires and fuel, and ethane is a hydrocarbon that is often emitted with methane from oil and gas production. Methyl chloroform is an industrial solvent which, like methane, can only be removed from the atmosphere by reacting with OH; Its emissions are much better known, so it usually determines how much OH is in the atmosphere. Researchers use lighter action donors to make conclusions about changes in sources or sinks of methane. For example, some have pointed to observations of increasing ethane concentrations in order to argue that fossil fuel extraction is the dominant driver of the methane spike.
Then there are the isotopes. After being analyzed in Dlugoken's laboratory, they are sent air samples to the Institute of Arctic and Alpine Research at the University of Colorado Boulder, where their carbon isotopes are measured. "Isotopes tell how much comes from microbes versus old, thermogenic sources, coal that has been laid off the soil," says Bruhwiler. Methane emitted by microbial sources (also known as biogen) tends to be lighter, with less carbon isotope C13 relative to C12, while methane from fossil fuels (thermogenic) and from burning biomass tends to be isotopically heavier. Measurements from INSTAAR and other research institutes clearly indicate that the methane of the atmosphere becomes more depleted in the C13 isotope.
Nevertheless, each type of clue has its limits. New works by Card and others have questioned the reliability of ethane as a useful, consistent tracer of methane. The ethane-to-methane conditions vary widely between different geological basins and the amount of ethane extracted from natural gas changes depending on its market value as a petrochemical raw material. Not everyone is convinced of isotope data either.
"Many of the communities are very skeptical, because the signatures for sources cover a rather high range," said Daniel Jacob, an atmospheric chemist at Harvard. Some sources share the same set of isotope fingerprints, making it difficult to distinguish between certain fossil and microbial sources. "Isotopes are a useful information, but I don't want to bet that the house only looks at isotope data."
Bruhwiler admits that there is uncertainty in the isotope, and very few studies have measured the isotopic isotopes of cattle and other ruminants, or bubbles out of wetlands. But she claims that fossil fuel gauge isotopes occupy a very narrow range of signatures limited in the overlap with microbial sources.
"At large global scales, the isotope limitation should be quite darn useful to tell us what is biogenic and what is the thermogen," she says.
In all this uncertainty, part of the global methane budget is more clearly quantified: emissions from US oil and gas production. This is largely due to the work of Steven Hamburg and the Environmental Defense Fund.
In the early 2000s, Hamburg was a professor of environmental science at Brown University. For a forest ecology course he taught, he drove the students out to a field scene every week in a natural gas powered van. Later, he had an epiphany: Although it seemed a cleaner, more effective alternative than a gasoline fueled vehicle, he had no idea how much gas it could leak out. But he knew that the leakage rate was crucial for the climate. Hamburg understood that methane was a powerful driver for presence heating, and as an ecologist he also knew that the rate of change in a system could be as important as size.
Despite its strength as a heating accelerator, managing methane leaks did not yet have the highest priority in climate policy circuits. "There was an opportunity," he says, "a large lever is sitting there that people could not yet see and use. We acknowledged that leverage existed."
When he became EDF Chief Scientist in 2008, he began to ask himself about the details of oil and gas supply chain leakage. "I got a regular response from companies:" We've covered it, we know what's going on, that's good. "When I pointed around, there was no good data anyone could show me back up."  In 2012, EDF launched a program to support an in-depth study of methane leaks throughout the US oil and gas supply chain. The effort has a total of more than 140 researchers from over 40 different academic and research institutions, providing more than 30 peer-reviewed publications and a much finer graded understanding of how much methane is leaking and from which fossil fuels are extracted across the country.
The culmination of the survey, published in Science last July, drew on ground-based measurements and observations from aircraft to estimate that methane emissions from the sector are 60 percent higher than estimates from stocks maintained by the Federal Environmental Protection Agency. That figure amounts to 2.3 percent of total natural gas production in the US. A leakage rate of only 4 percent would interrupt the climate benefits of burning gas instead of coal to generate electricity.
At global level, data on volatile oil and gas emissions are still sparse. For example, there are few measurements of, and very little access to, gas fields in Russia and Iran. Several years ago, Hamburg spoke with the atmospheric researcher Steven Wofsy about Harvard about the problem. What level of spatial granularity, those mused, would be needed to see and identify leaks from oil and gas fields and large spaces from space?
Thus MethanSAT was born. Last year, EDF announced that it would build and launch its own metropolitan satellite. "The metaphor I usually use, says Hamburg," we try to get away from a handmade small factory model, and we have to go to mass production. Distributing scientific teams is too expensive and laborious [at the global scale]. "
Today, the Wofsy is the science leader of the project. With a chuckle, he admits that it is an extremely ambitious" bonkers "company – an environmental organization trying to pull off a NASA project." EDF is very strategic, "he admits. "Their goal is to transform the oil and gas industry around the world by 2025." Stanford researchers recently suggest that more than half the volume of all natural methane emissions from natural gas comes from just the largest 5 percent of leaks. The actual number is slightly lower, there is a big deal among scientists tackling these "super-emitters" may be the most cost-effective methane reduction strategy, but first you have to find these plumes.MethanSAT will hunt for leaks over oil and gas fields that can be to just 10 parts per billion, against the backdrop of 1,850. "So you're looking for about 0.5 percent. If you are going to measure 0.5 percent you must have precision of about 0.1 percent, says Wofsy. "And some people think you can't do it. We think we can-not at every point in the field, but at the regional level."
Another unforeseen feature of MetanSAT is that the data it captures will be available to the public. "Our product is change in the oil and gas industry, and what motivates that change is transparent information about what they release," says Wofsy.
Of course, the satellite is still on the drawing board and many technical barriers hinder. Although everything goes according to plan, MetanSAT will not start producing recordable data until late 2022.
There is still evidence that it may already have a focus effect in some corners of the industry. Fiji George, head of climate and sustainability at Cheniere Energy, the largest exporter of liquid natural gas in the United States, has had a long career in the sector, including stints at Shell Oil and Southwestern Energy. "When you have this satellite technology, George says," 2022 Steve Hamburg could follow and say, "Hey, this facility, we mapped it every 14 minutes and found lots of emissions." Without knowing whether emissions are allowed or a maintenance event or a stochastic event that creates more uncertainty and anxiety and pressure on the industry. "
If the technical challenges can be overcome, George sees new methane detection technologies as something that industry should embrace if it wants natural gas to be a place in the energy mix decades from now on in a world that takes the Paris climate goals seriously.
" About this We will have five years from a completely different future when it comes to understanding what drives these changes "in global methane," says Wofsy. "Then someone could build another to half the cost and use it for another mission. You can begin to follow the agricultural sources, the landfills, the wetlands. You can watch any of them. "
Although there is no definite accusation yet, the community of methane detectives seems to be approaching to exclude an important suspect." The attribution that was quite popular a few years ago was increased natural gas, "Daniel Jacob says, referring to the combination of isotope evidence and atmospheric inversion models of his group and others. "It has made the wind out of the sails a little. We really don't see evidence of that. "
" My personal feeling is that the evidence strongly points to a natural biogenic source behind the increase. "
Some researchers, such as Robert Howarth of Cornell, are still convinced of the volatile emissions of oil and gas production – particularly fracking – are systematically underestimated and likely to be behind the global tip." It's a compelling story, "Pep says. Canadell, CEO of the Global Carbon Project, "but the larger community does not support that view."
In an influential 2016 paper in Nature a large group of researchers led by Stefan Schwietzke, a former NOAA researchers now working for EDF gathered the largest set of long-term data on isotopes from all methane-source microbial, fossil fuels, biomass burning, and found that methane emissions of fossil fuels were at least 60 percent greater than previous best estimates, but did not increase over time .
It is a counterintuitive arrival point. Oil and gas leaks are not responsible for the global inflation but they are a much bigger problem than previously thought. And studying them is still one of the most feasible ways to cut methane. The International Energy Agency estimates that as much as 50 percent of all oil and gas methane leaks can be set at zero net cost.
Even as suspicions shifted away from fossil fuels, they gather around tropical wetlands, the largest global source of methane. "When methane began to go, shortly afterwards, C13 started to go down," Dlugokencky says. Whatever drives the increasing concentrations "must be a methane source that is lighter than the average mixture of emissions to the atmosphere. What can it do? Microbial sources such as wetlands or ruminant animals."
Tropical wetlands can be the only source that is large and dynamic enough to explain both the magnet and the bluntness of the nail. It is unlikely that the number of livestock, the other major biogenic source, has increased fast enough to account for it.
Methane production from wetlands, can change rapidly from year to year, in response to meteorological shifts. Microbes in wetlands can produce more methane in response to increased precipitation, or warmer temperatures, or both. Or wetlands can grow in the area, more and more ground surfaces, either due to El Niño events or other climate variables.
"Wetlands are the ultimate potential carbon dioxide climate feedback that we do not fully understand," says Canadell. Researchers agree that models of these processes are getting better but still need much more work.
To map out the distribution of wetlands, researchers have relied on old aircraft of dubiousness, says Bruhwiler. They also use satellite images to identify areas flooded on land, but they are of limited use in the tropics, where overlying vegetation and heavy cloud cover can mask standing water. And scientists still know very little about the various isotopic signatures for microbial methane from wetlands.
In the long term, EDF-led collaboration effort to study oil and gas leaks, Eric Kort sees a potential road map to handle these sources of uncertainty. "This series of targeted studies that look at oil and gas basins on a number of scales has improved our understanding of emissions and the processes that govern it," he says. "The same measurement methods can be used to improve our understanding of wetlands."
" My personal feeling is that the evidence strongly points to a natural biogenic source behind the increase, "says Bruhwiler." And if that is true, it is important, because it can be an indication that there is climate feedback that occurs between the natural terrestrial biosphere and warming. "
When the world warms and parts of it get wet, microbes in tropical wetlands will cough even more methane? Will those who sleep in the Arctic permafrost release more of the big shop of frozen coal as methane than carbon dioxide, which leads to continued warming? Such feedback mechanisms are the elements of the global climate system that keep researchers awake at night. " The scientific issue we are facing now is the question of carbon dioxide climate feedback, says Bruhwiler. "The question that is very important is what comes down the road?"
Therefore, methane's mystery solves things. Looking for human fingerprints on these "natural" methane sources helps us understand what the future may mean. But even if new detection tools definitely identify wetlands as the main driver, our task will be the same: in addition to rapidly reducing carbon dioxide and other greenhouse gases, reducing methane emissions as far and as quickly as possible, from the sources we can control.
Despite all the arguments over what drives the increase since 2007, Card says, "over longer time frames, there is no debate. It is driven by human activities. Over the past 40 years, the increase over that period has been best described only by anthropogenic emissions. statements are not really controversial. "
" The most important thing we emphasize while sorting through this scientific debate, "says Hamburg," is that it in no way diminishes the ability to mitigate methane from particular sources, and to understand their impact on the climate. "It means to aggressively find and determine leaks from oil and gas infrastructure," he says. It also means transforming the way we grow, consume and dispose of food, Pep Canadell emphasizes.
Two new studies published in February seem to reinforce how urgent it is to study leaks. Dlugokencky and colleagues noted in their latest newspaper that whether it is due to a varying decline or change of tropical wetlands, the renewed growth of methane plans to scrambles to achieve the goal of staying below two degrees of warming over pre-industrial levels to nations gathered in Paris 2015. The methane's wild increase leaves much less room – and less time – in our global emissions budget than we expected.
However, another new study provides some measure of hope and citing modeling shows that reduction of anthropogenic methane emissions can still compensate for the "natural" leakage that thawing the Arctic will produce under warmer temperatures. If true, it would suggest a catastrophic feedback where human greenhouse gas emissions melt the planet's permafrost, which turns it from a large carbon storage unit into a large new source of planet-warming methane, leading to further warming – perhaps even being warded off. available to avoid the disappearance of the disappearing train scene.
"The bottom line," says Canadell, "is the methane that goes up and it doesn't look like it will end anytime soon."