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 (CH _4 ), driven by variations in rainfall that are in turn influenced by sea-surface temperature gradients over the Indian Ocean. Using satellite observations of CH _4 and an atmospheric chemistry-transport model, we quantified East African CH _4 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 CH _4 emissions of 6.2 ± 0.3 Tg CH _4 and 8.6 ± 0.3 Tg CH _4 , 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 CH _4 budget.

Keywords

• methane
• East Africa
• wetlands
• Indian Ocean Dipole