Abstract
Mitigating climate change requires a diverse portfolio of technologies and approaches, including negative emissions or removal of greenhouse gases. Previous literature focuses primarily on carbon dioxide removal, but methane removal may be an important complement to future efforts. Methane removal has at least two key benefits: reducing temperature more rapidly than carbon dioxide removal and improving air quality by reducing surface ozone concentration. While some removal technologies are being developed, modelling of their impacts is limited. Here, we conduct the first simulations using a methane emissions-driven Earth System Model to quantify the climate and air quality co-benefits of methane removal, including different rates and timings of removal. We define a novel metric, the effective cumulative removal, and use it to show that each effective petagram of methane removed causes a mean global surface temperature reduction of 0.21 ± 0.04°C and a mean global surface ozone reduction of 1.0 ± 0.2 parts per billion. Our results demonstrate the effectiveness of methane removal in delaying warming thresholds and reducing peak temperatures, and also allow for direct comparisons between the impacts of methane and carbon dioxide removal that could guide future research and climate policy.This article is part of a discussion meeting issue 'Rising methane: is warming feeding warming? (part 1)'.
Highlights
Atmospheric methane (CH4), the second most important greenhouse gas after carbon dioxide (CO2), has been steadily increasing at a rate of eight parts per billion per year over the past five years [1,2]
We presented our results using the average modelled perturbation lifetime for each shared socioeconomic pathways (SSPs) from 2020–2100, 9.6 years for SSP3-7.0 and 8.1 years for SSP1-2.6
These lifetimes incorporate tropospheric and stratospheric oxidation and soil sinks as well as the feedback factor that methane has on its own lifetime, which was calculated to be 1.35 for SSP3-7.0 and 1.25 for SSP1-2.6, in good agreement with literature values such as 1.28 for UKESM1 [7,9]
Summary
Atmospheric methane (CH4), the second most important greenhouse gas after carbon dioxide (CO2), has been steadily increasing at a rate of eight parts per billion (ppb) per year over the past five years [1,2]. Our results demonstrate the effectiveness of methane removal in delaying warming thresholds and reducing peak temperatures, and allow for direct comparisons between the impacts of methane and carbon dioxide removal that could guide future research and climate policy.
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