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Abstract Methane (CH 4 ) is a potent greenhouse gas with a warming potential 84 times that of carbon dioxide (CO 2 ) over a 20‐year period. Atmospheric CH 4 concentrations have been rising since the nineteenth century but the cause of large increases post‐2007 is disputed. Tropical wetlands are thought to account for ∼20% of global CH 4 emissions, but African tropical wetlands are understudied and their contribution is uncertain. In this work, we use the first airborne measurements of CH 4 sampled over three wetland areas in Zambia to derive emission fluxes. Three independent approaches to flux quantification from airborne measurements were used: Airborne mass balance, airborne eddy‐covariance, and an atmospheric inversion. Measured emissions (ranging from 5 to 28 mg m −2 hr −1 ) were found to be an order of magnitude greater than those simulated by land surface models (ranging from 0.6 to 3.9 mg m −2 hr −1 ), suggesting much greater emissions from tropical wetlands than currently accounted for. The prevalence of such underestimated CH 4 sources may necessitate additional reductions in anthropogenic greenhouse gas emissions to keep global warming below a threshold of 2°C above preindustrial levels.
Shaw et al. (Fri,) studied this question.