Wikipedia Deep Dive

Atmospheric methane

13 min read

The Invisible Blanket Getting Thicker

Here's a number that should stop you cold: since the Industrial Revolution began around 1750, the concentration of methane in Earth's atmosphere has increased by 160 percent. We're now breathing air with 2.6 times more methane than humans ever encountered before the steam engine. And the kicker? This is the highest concentration in at least 800,000 years.

That's not a typo. Eight hundred thousand years.

To put that timeframe in perspective, 800,000 years ago, Homo sapiens didn't even exist yet. Our ancestors were still figuring out fire. The ice ages came and went, came and went, eight full cycles of glaciers advancing and retreating across continents. Through all of that natural climate chaos, methane levels never reached what they are today.

And we did this in about 275 years.

Why Methane Punches Above Its Weight

You've probably heard of carbon dioxide. It gets all the press, the protests, the international agreements. But methane is carbon dioxide's scrappy, underestimated cousin—and molecule for molecule, it's far more dangerous.

Over a 20-year period, methane traps 84 times more heat than the same amount of carbon dioxide. Eighty-four times. If greenhouse gases were boxers, carbon dioxide would be a heavyweight who can go fifteen rounds, while methane would be a lighter fighter who can knock you out in the first.

The difference is staying power. Methane doesn't last as long in the atmosphere as carbon dioxide. After about a century, methane's warming effect drops to about 28 times that of carbon dioxide. Carbon dioxide, meanwhile, hangs around for centuries, even millennia, continuing to warm the planet long after we've stopped emitting it.

This creates an interesting strategic situation for climate action. Cutting methane provides fast results—you can bend the temperature curve within decades. Cutting carbon dioxide provides permanent results—but the benefits take longer to show up. We need to do both, but for different reasons.

The Science of Warming, Explained Simply

Scientists measure the human impact on Earth's climate using something called radiative forcing, which sounds complicated but is actually quite intuitive. Think of it this way: the sun sends energy to Earth, Earth absorbs some and reflects some back to space. Radiative forcing measures how much we've changed that balance.

The unit is watts per square meter. If Earth were a perfect black surface facing the sun, it would receive about 1,361 watts per square meter. The greenhouse gases we've added to the atmosphere trap some of the outgoing energy, like putting a blanket on a sleeping person. More blanket, more warmth.

Methane's direct contribution to this extra blanket effect is about 0.5 watts per square meter compared to 1750. That might sound small, but spread it across the entire surface of the Earth—all 510 million square kilometers—and you're talking about an enormous amount of extra energy trapped in the climate system.

And recent research suggests we've been underestimating methane's impact. A 2016 study published in Geophysical Research Letters found that previous calculations had missed something important: methane absorbs incoming solar radiation, not just outgoing infrared radiation. When scientists incorporated this shortwave absorption into their models, methane's warming effect jumped by 20 to 25 percent.

Where Does All This Methane Come From?

Methane has two main natural origins, and both involve life doing what life does.

The first is a process called methanogenesis—the production of methane by microorganisms. These are ancient creatures, bacteria and archaea that thrive in environments without oxygen. Swamps, rice paddies, the bottoms of lakes, the guts of termites: anywhere organic matter decomposes without oxygen, these microbes are busy converting carbon into methane and releasing it into the air.

The second major source is ruminant animals—cattle, sheep, goats, and their wild relatives. These animals have specialized stomachs that use microbial fermentation to break down tough plant fibers. The process works, but it produces methane as a byproduct. Every burp from a cow is a tiny puff of greenhouse gas.

A single dairy cow can produce between 70 and 120 kilograms of methane per year. There are roughly one billion cattle on Earth. The math is sobering.

Then there are the sources we've created. Natural gas is primarily methane, and it leaks from wells, pipelines, and processing plants. Coal mines release methane that's been trapped underground for millions of years. Landfills are essentially giant anaerobic digesters, with buried garbage slowly releasing methane as it decomposes. Rice cultivation, which feeds billions of people, creates flooded conditions perfect for methane-producing microbes.

And waiting in the wings is a source that terrifies climate scientists: Arctic permafrost. For thousands of years, organic matter has been frozen in the soils of Siberia, Alaska, and northern Canada. As the Arctic warms—and it's warming faster than anywhere else on Earth—this permafrost is thawing, and the ancient organic matter is decomposing, releasing its stored carbon as methane. This is a feedback loop: warming releases methane, methane causes more warming, more warming releases more methane.

How Do We Even Measure This Stuff?

You can't see methane. You can't smell it (natural gas companies add the smell for safety). So how do scientists know how much is in the atmosphere, and where it comes from?

The traditional method is gas chromatography, a laboratory technique that separates gases by passing them through a column filled with specialized materials. Different gases travel through the column at different speeds, allowing scientists to identify and measure each component. It's reliable but slow—you need to collect air samples, bring them to a lab, and analyze them one by one.

Modern measurements increasingly rely on spectroscopy, which exploits the fact that different molecules absorb light at different wavelengths. Shine infrared light through a sample of air, measure which wavelengths get absorbed, and you can determine exactly how much methane is present. This can be done remotely, from satellites or aircraft, allowing scientists to map methane concentrations across entire continents.

The most precise technique today is something called cavity ring-down spectroscopy. Imagine a small chamber with mirrors at each end. You fire a laser pulse into the chamber, and it bounces back and forth thousands of times before the light decays. If there's methane in the chamber, it absorbs some of that laser light, and the decay happens faster. By measuring exactly how quickly the light fades, scientists can detect methane at concentrations of parts per trillion—that's like finding a few specific drops in an Olympic swimming pool.

The Mysterious Plateau and the Alarming Surge

The history of atmospheric methane since we started measuring it directly in the 1970s tells a strange story.

For most of the late 20th century, methane concentrations rose steadily. This made sense: more agriculture, more fossil fuel extraction, more people doing more things that release methane. The increase wasn't as fast as carbon dioxide, but it was relentless.

Then, around 1999, something odd happened. Methane levels stopped rising. For nearly a decade, the concentration stayed essentially flat, hovering around 1,770 parts per billion. Scientists were puzzled. Had natural sinks increased? Had human emissions somehow stabilized without anyone intending it? No one could definitively explain the plateau.

Then, around 2007, methane started rising again. And this time it didn't stop.

By 2019, global methane had reached 1,866 parts per billion. By 2022, it hit 1,912 parts per billion. The year 2021 saw the largest single-year increase ever recorded. We've now reached 260 percent of pre-industrial levels.

What's driving this surge? This is where the science gets genuinely controversial.

The Great Methane Mystery

Scientists can do something clever to figure out where methane comes from: they analyze its isotopes. Carbon atoms come in slightly different versions—most carbon is carbon-12, but some is carbon-13, which has an extra neutron and is therefore slightly heavier. Different sources of methane have different ratios of these isotopes, like fingerprints.

Methane from biological sources—wetlands, cow burps, rice paddies—tends to be "lighter," with relatively less carbon-13. Methane from burning fossil fuels or biomass tends to be "heavier," with more carbon-13.

Here's what's puzzling scientists: as methane concentrations have risen since 2007, the ratio of carbon-13 in atmospheric methane has been declining. This suggests the new methane is coming primarily from biological sources, not from increased fossil fuel burning. The National Oceanic and Atmospheric Administration, known as NOAA, has concluded that wetlands and agricultural emissions are the main culprits.

But not everyone agrees.

The problem is that isotope ratios reflect both sources and sinks. If the processes that destroy methane are also changing, the isotope signal could be misleading. Several research groups using sophisticated computer models have found that fossil fuels, agriculture, and waste management (landfills, manure pits, wastewater treatment) might each account for roughly half the increase, with human activities overall dominating the rise.

The honest answer is: we don't know for certain. This is an active area of scientific debate, and the answer matters enormously for policy. If the surge is mostly from wetlands responding to climate change, that's a feedback loop we may not be able to control. If it's from fossil fuel leaks and agricultural practices, those are things we could potentially fix.

The Atmospheric Destruction Machine

What keeps methane from building up even faster? The atmosphere has a built-in cleaning system.

The main methane destroyer is a molecule called the hydroxyl radical, written as OH. It's just one hydrogen atom bonded to one oxygen atom, and it's ferociously reactive. Hydroxyl radicals are sometimes called the "detergent of the atmosphere" because they react with and break down an enormous variety of pollutants.

When a hydroxyl radical meets a methane molecule in the troposphere—the lower atmosphere where weather happens—it strips away a hydrogen atom. This kicks off a chain of chemical reactions that eventually converts the methane into carbon dioxide and water vapor. About 90 percent of atmospheric methane meets its end this way.

The process is most active in the tropics, where warm, moist, sunny conditions generate the most hydroxyl radicals. As tropical air rises, it carries methane upward through the troposphere, into the stratosphere (the layer where the ozone layer exists), and the methane is gradually destroyed as it ascends.

But here's a complication that creates another feedback loop. When methane is destroyed, it consumes hydroxyl radicals. More methane in the atmosphere means fewer hydroxyl radicals available to destroy it. This extends methane's atmospheric lifetime. The more we emit, the longer each molecule sticks around.

And the destruction products aren't necessarily harmless. Methane oxidation produces carbon dioxide, which is a greenhouse gas. It also produces water vapor, which in the stratosphere acts as an exceptionally potent greenhouse gas. This stratospheric water vapor adds about 15 percent to methane's overall warming effect.

The Nonlinear Nightmare

Climate scientist V. Ramanathan noted something concerning back in 1998: the relationship between methane and warming might not be linear.

Most climate models assume that if you double the methane, you roughly double the warming effect (with some adjustments for logarithmic scaling). But Ramanathan pointed out that water vapor and ice clouds in the cold lower stratosphere are extremely efficient at trapping heat. If methane concentrations get high enough to significantly increase stratospheric water vapor, the warming effect could accelerate faster than expected.

This is the nightmare scenario that haunts climate scientists: nonlinear effects, tipping points, feedback loops that spiral out of control. We don't know exactly where these thresholds lie, or whether we've already crossed some of them.

The Arctic is the canary in this particular coal mine. Methane concentrations in the Arctic have been measured at 1,850 parts per billion—over twice as high as at any point in the last 400,000 years. The permafrost continues to thaw. The feedback loop continues to spin.

The Case for Acting on Methane

There's a reason methane has become, as the Substack article notes, "trendy" among climate policymakers. It offers something carbon dioxide doesn't: quick wins.

Because methane doesn't persist in the atmosphere for centuries, cutting methane emissions shows results within years, not decades. A 2018 study led by William Collins found that reducing atmospheric methane by the end of the century could "make a substantial difference to the feasibility of achieving the Paris climate targets." It would give us more room to maneuver, more time to tackle the harder problem of carbon dioxide.

The sources are also, in many cases, addressable with existing technology. Plugging leaks in natural gas infrastructure. Capturing methane from landfills and using it as fuel. Improving manure management on farms. Draining rice paddies periodically instead of keeping them continuously flooded. Feeding cattle seaweed additives that reduce their methane burps.

None of these are silver bullets. None of them are easy. But they're possible in ways that quickly eliminating all fossil fuel combustion is not.

The Limits of the Methane Strategy

Here's the catch, and it's an important one: methane mitigation cannot substitute for carbon dioxide mitigation.

The physics are unforgiving. Carbon dioxide accumulates. Every ton we emit adds to the total already in the atmosphere, and most of it stays there for centuries. Even if we cut methane to zero tomorrow—a practical impossibility—the carbon dioxide we've already emitted would continue warming the planet for generations.

Methane buys us time. It doesn't solve the problem.

There's also the scale issue. Methane contributes about 3 percent of greenhouse gas emissions by mass, yet accounts for 23 percent of the warming effect. This leverage works in reverse too: even dramatic methane reductions can only do so much when carbon dioxide emissions continue rising.

The Global Carbon Project, a consortium of over fifty international research institutions, maintains what they call the Global Methane Budget, tracking sources and sinks across the planet. Their work, updated every few years using data from over 100 monitoring stations, shows that the balance between methane production and destruction is still not fully understood. In 2013, scientists couldn't explain why methane had stopped increasing in the late 1990s. Today, they're still debating why it's rising so fast.

What we do know is that the overwhelming cause is human activity. The increase from 722 parts per billion in 1750 to over 1,900 parts per billion today didn't happen by accident. It happened because of choices: how we grow food, how we extract energy, how we dispose of waste.

Different choices could bend the curve. But they would have to be made soon, and they would have to be made at scale. The atmospheric blanket is getting thicker every year, and methane is one of the heaviest threads being woven into it.

The next 800,000 years are watching.