Tropical forest vulnerability to ENSO induced extremes in a changing climate

Tropical forests are a crucial carbon sink to rising atmospheric CO₂; however, they could be experiencing a tipping point. Their ability to remove carbon from the atmosphere is decreasing due to continuous deforestation from human practices and tree mortality from frequent climatic extremes. Therefore, it is very important to study the vulnerability of tropical forests to climate change. Compared with changes in mean climates, the ecosystem resilience is more sensitive to changes in climate variability. El Niño-Southern Oscillation (ENSO) is the most important mode of climate variability on interannual to decadal time scales and exerts extensive impacts on Earth's climate and ecosystems through prominent teleconnections. It significantly affects the intensity and occurrence of extreme events worldwide. Despite the inter-model discrepancies in the projected changes of ENSO properties itself, the frequency and intensity of strong/extreme ENSO events tend to increase in the future as well as the strength of ENSO impacts and teleconnections over continental regions. It leads to increased interannual variability (IAV) in temperature, precipitation and radiation and wildfire frequency. Thus, an ENSO event of a given strength could produce more extreme impacts and induce more stress on global ecosystems. In this study, we will investigate the vulnerability of tropical forests to the projected increases of ENSO-induced extremes and their responses to global climate by analyzing multi-model results from the CMIP6 archive. We will delineate the ENSO induced effects from the trends of mean climates by comparing the model results on the ENSO years with those on the normal years. Initial results showed that the ENSO-induced extremes have great impacts on tropical forests and the enhanced IAV induced by ENSO will increase vulnerability of tropical forests, especially for those forests in locations that do not currently experience strong IAV.