Every time you breathe, you probably inhale a few trace amounts of methane, one of the most powerful and important gases on the planet.
Methane, at its core, is fairly simple: It's just one carbon molecule surrounded by four hydrogen molecules. Although it's not one of the primary gases in our atmosphere — those would be nitrogen, oxygen and argon — it is one of the most plentiful organic compounds on Earth. But even though it's everywhere, you would never know it's there, as methane is colorless, odorless and tasteless.
Don't let its invisibility fool you, though. Methane could have major roles — both good and bad — in the future of life on Earth.
A few basics
Methane is a natural substance that can be produced over time through biological routes — that's what creates natural gas, of which methane is the primary component — as well as technological processes or other synthetic means. If produced underground, it can last for millennia. Once in the atmosphere, it will break down in anywhere from nine to 15 years as it is exposed to oxygen and water vapor.
But while it's in the atmosphere, it's pretty potent stuff. Not only is methane a greenhouse gas like carbon dioxide, the primary driver of human-induced climate change, but its heat-trapping effects are even stronger than those of CO2.
Scientists use a metric called global warming potential (GWP) to compare how 1 ton of a given gas traps heat on Earth compared with 1 ton of CO2. And according to the Intergovernmental Panel on Climate Change (IPCC), methane has a GWP of 34 on a 100-year time scale, meaning it's 34 times more potent of a greenhouse gas than CO2 over a century. But since methane is so short-lived in the air, its GWP is even higher on a shorter time scale: Over 20 years, for instance, it has a huge GWP of 86.
And even though methane itself doesn't stay in the atmosphere as long as CO2, the long-term effects of its short-term temperature surges can be irreversible. Melting sea ice in the Arctic, for example, creates an insidious feedback loop.
According to the U.S. Environmental Protection Agency (EPA), methane accounts for about 10 percent of the greenhouse gas emissions from human activities like natural gas systems, landfills, coal mining and manure-management systems. But at the same time, methane — especially in natural gas — is an important fuel source, one that produces fewer greenhouse gases when burned than coal or oil.
Methane's potential as energy
Methane has quickly become a go-to power source in recent years, especially in the United States. According to the U.S. Energy Information Administration, Americans obtained 29 percent of their energy from natural gas in 2015, while coal represented just 16 percent — quite a drop from coal's 2008 share of 50 percent. In 2011, the U.S. produced more natural gas than coal for the first time since 1981.
While still a nonrenewable (and climate-altering) resource, natural gas does produce fewer dangerous emissions than coal does. According to the EPA, natural gas "produces half as much carbon dioxide, less than a third as much nitrogen oxides, and 1 percent as much sulfur oxides at the power plant."
Natural gas has potential beyond power plants, too. It can be compressed to fuel vehicles, and a growing field of research aims to make batteries powered by methane. The methane from landfills can also be tapped to generate energy, as can the methane emitted by manure on hog farms. In the latter cases, where methane is produced by biological means, it's actually more sustainable than natural gas and uses materials to generate electricity that would otherwise go to waste.
Methane's risk to the climate
In addition to city lights, this 2012 NASA satellite image shows an array of gas flares across North Dakota. (Photo: NASA)
Not only does burning natural gas release CO2 into the atmosphere, but the very production of natural gas is also a climate risk, as methane often escapes during extraction and transportation. This may have been under control for a while, and a 2012 study by NASA found that greenhouse gases from the 1980s through 2005 tapered off because less methane was escaping during the exploration process.
Unfortunately, levels of atmospheric methane have been on the rise since 2007, and some scientists say the growth of hydraulic fracturing, also known as fracking, plays a key role in that increase. (A recent NOAA study found little connection between U.S. drilling and rising methane emissions, yet still noted "methane leakage must be limited for there to be a climate benefit in switching from coal to natural gas.")
To reduce the threat of atmospheric methane, the Obama administration finalized its Gas Reduction Rule in 2016, a measure designed to limit venting, flaring and leaking of natural gas from oil and gas operations on public lands. This rule is expected to reduce those forms of gas waste by 40 percent, avoiding nearly 170,000 tons of methane emissions every year — roughly equivalent to eliminating the annual greenhouse-gas emissions from 860,000 to 890,000 vehicles.
After the 2016 U.S. elections, however, the rule seemed likely to be overturned by a Republican-led Congress and President Trump. Although methane waste has been a bipartisan issue, the Senate was widely expected to vote to repeal the rule in May 2017, as the House had already done along party lines. Yet in a surprise turn of events, enough Senate Republicans opposed repeal for the vote to fail, 49-51.
Because the Congressional Review Act gives Congress 60 days to nix executive-branch regulations after their passage, the Senate vote came near the end of the window to repeal the Gas Reduction Rule. But even if this regulation does endure, the U.S. and countries around the world still face a daunting struggle to manage the dangers of atmospheric methane.
Like carbon dioxide, methane isn't a bad gas in and of itself — but humanity is pushing more of it into the atmosphere than ever before. Understanding where it comes from and developing ways to mitigate it will play an important role in maintaining the Earth's climate for the future.
Editor's Note: This story has been updated since it was first published in September 2012.