Rain-fed pulses of methane from East Africa during 2018–2019 contributed to atmospheric growth rate

Abstract

East Africa is a key location for wetland emissions of methane (CH₄), driven by variations in rainfall that are in turn influenced by sea-surface temperature gradients over the Indian Ocean. Using satellite observations of CH₄ and an atmospheric chemistry-transport model, we quantified East African CH₄ emissions during 2018 and 2019 when there was 3-σ anomalous rainfall during the long rains (March-May) in 2018 and the short rains (October-December) in 2019. These rainfall anomalies resulted in CH₄ emissions of 6.2±0.3 Tg CH₄ and 8.6±0.3 Tg CH₄, in each three month period respectively, and represent a 10% and 37% increase compared to the equivalent season in the opposite year, when rainfall was close to the long-term seasonal mean. We find the additional short rains emissions were equivalent to over a quarter of the growth in global emissions in 2019, highlighting the disproportionate role of East Africa in the global CH₄ budget.