The unexpected culprit that could throw a wrench in the world’s efforts to stop climate change? Runaway methane levels. Researchers monitoring air samples have noticed an alarming observation: Methane levels are on the rise and no one’s quite sure why.

NOAA’s Earth System Research Laboratory scientists have been analyzing air samples since 1983. Once a week, metal flasks containing air from around the world at different elevations find their way to the Boulder, Colorado, lab. The scientists look at 55 greenhouse gases, including methane and its more-famous climate villain, CO2.

You might know methane as the stuff of cow farts, natural gas, and landfills. It’s also an incredibly potent greenhouse gas, absorbing heat