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Extreme El Niño events cause short-term CO₂ fluctuations, researchers find

A recent study challenges previous assumptions about the connection between CO₂ in the atmosphere and temperatures in the tropics. Between 1959 and 2011, the CO₂ content in the atmosphere responded twice as strongly to temperatures in the tropics than before.

This has often been attributed to increasing droughts in the tropics and to changes in carbon cycle responses caused by climate change. However, the new study conducted by researchers from the Max Planck Institute for Biogeochemistry and Leipzig University suggests that a small number of particularly strong El Niño events could be responsible for this.

Their findings are published in the journal Science Advances.

Both tropical and non-tropical ecosystems absorb large amounts of carbon that were previously released into the atmosphere through human CO₂ emissions. Globally, land surface ecosystems act as a carbon sink and absorb on average around a third of human CO₂ emissions. These ecosystems are therefore a natural buffer for climate change.

In the 1980s and 1990s, however, researchers observed an increased fluctuation in global carbon storage on land, and it appeared that the CO₂ growth rate was particularly sensitive to temperatures in the tropics. Researchers from Jena and Leipzig found that this "doubling" of sensitivity was caused by the increased occurrence of El Niño events in the 1980s and 1990s compared to 1960–1979.