The amount and proportion of the powerful heat-trapping gas methane that humans spew into the atmosphere is rising, helping to turbocharge climate change, a new study finds.

Tuesday’s study finds that in 2020, the last year complete data is available, the world put 670 million tons (608 million metric tons) of methane in the air, up nearly 12% from 2000. An even more significant finding in the study in Environmental Research Letters was the source of those emissions: those from humans jumped almost 18% in two decades, while natural emissions, mostly from wetlands, inched up just 2% in the same time.

Methane levels in the air are now 2.6 times higher than in pre-industrial times, the study said. Methane levels in the air had plateaued for a while in the early 2000s, but now are soaring. Humans cause methane emissions by burning fossil fuels, engaging in large-scale agriculture and filling up landfills.