Supplementary material from "Tropical land carbon cycle responses to 2015/16 El Niño as recorded by atmospheric greenhouse gas and remote sensing data"

The outstanding tropical land climate characteristic over the past two to three decades is rapid warming, while there are no significant large-scale precipitation trends. Warming is expected to continue but effects on tropical vegetation are unknown. El Niño-related heat peaks may provide a test bed of what to expect. Here we analyse tropical land carbon cycle responses to the 2015/16 El Niño climate anomalies using an atmospheric transport inversion. Based on the global atmospheric CO₂ record and long-term behaviour of the global carbon cycle, we find no obvious signs of anomalously large carbon release during the 2015/16 El Niño compared to earlier El Niño events. We find roughly equal net carbon release anomalies from Amazonia and tropical Africa, approximately 0.5 PgC each, and smaller carbon release anomalies from tropical East Asia and Southern Africa. Atmospheric CO anomalies reveal fire carbon release from tropical East Asia peaking in October 2015 while Amazonian fires played a smaller role. The positive flux anomalies are consistent with the downregulation of primary productivity during peak negative near-surface water anomaly (October 2015 to March 2016) as diagnosed by solar-induced fluorescence. Finally, we find an anomalous positive flux to the atmosphere from tropical Africa early in 2016, coincident with substantial CO release.