The El Nino-Southern Oscillation (ENSO) is a major source of global climate variability and significantly impacts the United States. Understanding how external forcing, such as the eruption of volcanoes that inject sulfate aerosols into the atmosphere and reduce the amount of incoming shortwave radiation, impact ENSO is essential to better understand climate model sensitivity to volcanoes, as well as potential risks of solar radiation management approaches.
The link between ENSO and volcanism is difficult to assess for a number of reasons and has been debated among scientists for over 40 years. Past studies using tree ring proxies have suggested a relationship between the two, with multiple mechanisms proposed; while studies using coral proxies have suggested no relationship. A recent study published in Nature Communications, funded in part by the Climate Observations and Monitoring program, revisits examining this link since new data have become available and there have been advancements in paleoclimate data assimilation. The study integrates both tree ring and coral proxy data and combines this with modeling results that yield insight into the role for both initial and boundary conditions in impacting the ENSO-volcanism relationship. They find no ENSO-volcanism relationship over the last millennium and are in agreement with Dee et al. 2020 (a previously funded COM study), and disagreement with many others; however they highlight the many caveats in working with paleoclimate proxies even with advancements in data assimilation. Based on their analysis and others’ prior work, they suggest that a longer time series of high resolution proxy records (beyond the past millennium into the Holocene) may be needed to confidently conclude how volcanism impacts ENSO dynamics.
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For more information, contact Virginia Selz.