Abstract
The growth rate of the atmospheric abundance of methane (CH4) reached a record high of 15.4 ppb yr−1 between 2020 and 2022, but the mechanisms driving the accelerated CH4 growth have so far been unclear. In this work, we use measurements of the 13C:12C ratio of CH4 (expressed as δ13CCH4) from NOAA’s Global Greenhouse Gas Reference Network and a box model to investigate potential drivers for the rapid CH4 growth. These measurements show that the record-high CH4 growth in 2020–2022 was accompanied by a sharp decline in δ13CCH4, indicating that the increase in CH4 abundance was mainly driven by increased emissions from microbial sources such as wetlands, waste, and agriculture. We use our box model to reject increasing fossil fuel emissions or decreasing hydroxyl radical sink as the dominant driver for increasing global methane abundance.
Really interesting stuff. Going to give a close read for insight into what is driving the microbes to act this way.
Edit: “Atmospheric δ13CCH4 does not allow us to differentiate between anthropogenic microbial sources (livestock, landfills) and natural ones (wetlands), so further study is necessary to investigate the potential climate feedback hypothesis”.
So, their simulations suggest its the microbes, but without more study we don’t know if it’s us causing it directly or natural sources (and they can’t rule out anthropogenic influences on natural sources either). So, don’t let anyone tell you this proves humans aren’t driving climate change or methane emissions, because that’s not what it says.
