Emissions of global warming-causing methane gas are on the rise across the globe and reaching levels unseen in at least two decades, according to a new study, indicating researchers must pay closer attention to the potent greenhouse gas as they work to combat climate change.
The new study, published in the journal Environmental Research Letters, shows that methane levels began to increase dramatically around 2007 and even more so in 2014. Atmospheric methane concentration increased by about 0.5 parts per billion annually in the early 2000s. That number had jumped 20-fold by 2014, according to the study.
Researchers largely attribute the spike to agriculture, though methane emissions that escape during energy development also play a role. The emissions mostly come from the tropics, likely due to rice patties and cattle ranches there, according to the study. Still, researchers said that precise details about what caused the spike remain unclear.
“Unlike carbon dioxide, where we have well described power plants, almost everything in the global methane budget is diffuse,” says study author Robert Jackson, a professor at Stanford University, in a news release. “From cows to wetlands to rice paddies, the methane cycle is harder.”
Methane is a heat-trapping gas that contributes to man-made climate change, but until recently policymakers tasked with fighting global warming have largely focused on addressing more abundant carbon dioxide. Recent data has shown that carbon emissions have stagnated in recent years, at least in part because of global efforts to address the issue.
Climate scientists say dealing with methane emissions will play a crucial role in meeting the international goal embedded in the Paris Agreement to keep global temperatures from rising more than 2°C (3.6°F) above pre-industrial levels by 2100. The Obama administration issued several regulations—primarily in the energy sector—to address the pollutant in the final years of his presidency. Methane is released during the fracking process and can escape from natural gas pipelines unnoticed. And as natural gas—now the country's leading power source for electricity—continues to rise, so too could methane emissions from that sector.
The researchers hope the report will encourage increased scrutiny on the contribution of agriculture to man-made climate change, which is not often the primary focus of environmental policymakers. Livestock like cows, and land use changes, both result in emissions. “When it comes to methane , there has been a lot of focus on the fossil fuel industry," says Jackson. "But we need to look just as hard if not harder at agriculture."