Atmospheric methane removal may reduce climate risks

Atmospheric methane removal—breaking down the 1.9 parts per million (ppm) of methane in the atmosphere faster than natural systems already do—may be a critical tool to address the methane emissions gap and lower climate risks [1].

Limiting peak global warming to 1.5 °C or 2 °C will require both reaching net-zero emissions of long-lived greenhouse gases (particularly carbon dioxide) to stabilize temperatures and cutting short-lived climate pollutants (particularly methane) to lower near-term warming. The rate of near-term warming will dictate the prevalence of climate extremes and the speed at which humanity and nature must adapt [2]. The higher the peak temperature, the greater the risk of passing various Earth system tipping points, initiating irreversible changes and feedback loops that may destabilize climate and potentially societies [3].

Even if all currently available methane emissions reductions approaches were implemented simultaneously, we show below that there would still be a methane emissions gap between the resulting level of emissions and what is needed to limit global warming to 2 °C. This emissions gap will likely consist of two parts: residual hard-to-abate anthropogenic emissions and anthropogenically amplified natural emissions.

To be consistent with a scenario that keeps global warming below 2 °C (e.g. SSP1-2.6 [4]), anthropogenic methane emissions must be cut by nearly 50% from today's ∼380 million metric tons (Mt) per year down to ∼200 Mt yr−1 or less by 2050 [4, 5]. Lowering methane emissions to 200 Mt yr−1 would require the global implementation of all currently technologically feasible emissions reductions simultaneously [6].

Meanwhile, anthropogenically amplified natural emissions are already rising as temperatures rise and precipitation patterns change [7]. Wetland methane emissions are predicted to increase by 20–100 Mt yr−1 above their baseline by 2050 depending on the global emissions trajectory and climate sensitivity [7, 8]. As global warming passes poorly understood thresholds, abrupt permafrost thaw could release a further 5–20 Mt yr−1 of methane by 2050 [9]. Together, these systems could release 25–120 Mt yr−1 of methane by 2050, contributing ∼0.05 °C–0.2 °C of warming [10] that is not accounted for in IPCC scenarios [4].

By 2050, the methane emissions gap for a 2 °C-consistent scenario will therefore be the sum of the residual anthropogenic emissions that remain in excess of 200 Mt yr−1 and the predicted 25–120 Mt yr−1 of unaccounted-for anthropogenically amplified natural emissions.

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