Plot of methane emissions with time, noting the target amount for 2050
Anthropogenic emissions of methane have grown from 2000 to 2018 due to increased emissions from landfills, agriculture, and using fossil fuels (as identified by colored shading). The black dots show the 2010 reference emissions sum and the lower 2050 target needed to avoid exceeding 2°C global warming. The red dot shows that the 2050 target for these CH4 sources must be lower still if wetland emissions increase due to a positive feedback to climate change. See the Viewpoint by Thompson [2021] for more details. Credit: Thompson, 2021, Figure 1
Source: AGU Advances

Global methane emissions are increasing, but we are not sure why. Positive feedbacks of CH4 emissions from wetlands to climate change may be contributing to the increase. Ma et al. [2021] combine biogeochemical models and satellite-derived CH4 concentration observations to examine climatic feedbacks to emissions from wetlands, from the equator to the poles. Tropical wetlands emit the 72% of global wetland emissions of CH4, and those emissions are shown to be most sensitive to changes in precipitation. In contrast, higher latitude wetlands emit much less overall, but their emissions are highly sensitive to temperature. In a companion Viewpoint, Thompson [2021] describes the novel way that Ma et al. [2021]  compare bottom-up estimates based on land surface models to those derived from a top-down atmospheric inversion model. She also notes that positive feedbacks of wetland CH4 emissions to climate change will require still stronger mitigation efforts in other sectors to avoid exceeding 1.5°C or even 2.0°C global warming.

Citation: Ma, S., Worden, J., Zhang, Y., Poulter, B., Cusworth, D. et al. [2021]. Satellite constraints on the latitudinal distribution and temperature sensitivity of wetland methane emissions. AGU Advances, 2, e2021AV000408.

—Eric Davidson, Editor, AGU Advances

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