After carbon dioxide, methane is the next most influential greenhouse gas, responsible for a fifth of all global warming. The amount of methane in our atmosphere is more than double what it was 250 years ago, and the rate of increase has grown even more in the last few years. Though scientists know that methane comes from a variety of sources, from cattle and rice fields to coal mines and landfills, they aren’t sure what’s been causing this recent, rapid rise. To help figure that out, NASA has created a 3D view of the methane swirling around our atmosphere.
“It’s really difficult for us to understand why there’s been this doubling of methane in the atmosphere, which then means it’s difficult for us to mitigate those sources to reduce the amount of methane that’s being emitted,” says Ben Poulter, a research scientist in the earth sciences division at NASA’s Goddard Space Flight Center. Along with being a harmful greenhouse gas, methane is a precursor to surface ozone (sometimes called ground ozone), which is an air pollutant that is harmful to both humans and plants. This new 3D simulation, he says, could help scientists understand where all this methane is coming from.
Using data from emissions inventories, which estimate the pollutants discharged into the atmosphere from fossil fuels, agriculture, and fires, along with simulations of natural methane emissions from wetlands, the 3D simulation shows where methane emissions are concentrated across the globe, as well as how they may move around our atmosphere because of factors such as wind.
Just as forests act as carbon sinks, there are also some natural methane sinks that remove methane from our atmosphere through a chemical reaction. This removal is included in the NASA 3D model, but because methane emissions have increased so much, the sinks aren’t removing proportionally as much methane from our atmosphere as they used to, and that’s why there’s been such an increase in the concentrations.
There’s also a mismatch, Poulter explains, between what countries are reporting in terms of their methane emissions and what scientists are measuring in the atmosphere. “One outcome of simulations like this,” he says of NASA’s 3D methane model, “could be to help countries update their emissions inventory and better understand the uncertainties in the reporting.”
Compared to carbon, methane doesn’t stay in the atmosphere that long—about nine years versus carbon dioxide’s more than 100-year lifespan—but the impact that methane has during that time is huge. Carbon has been, rightly, the focus when it comes to curbing climate change, but that means methane may often be overlooked as a contributing factor. “If we can reduce methane concentrations, we could have a short-term positive impact on reducing greenhouse gases,” Poulter says, “and that could give us more time to develop strategies to reduce CO2 emissions that are more strongly linked with energy production.”