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No consistent ENSO response to volcanic forcing over the last millennium

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Science  27 Mar 2020:
Vol. 367, Issue 6485, pp. 1477-1481
DOI: 10.1126/science.aax2000

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Not a big deal after all

Do volcanic eruptions affect El Niño–Southern Oscillation (ENSO) variability? Models indicate that sulfate aerosols resulting from large eruptions can initiate an El Niño–like response in the tropical Pacific, but observations have not shown evidence of such behavior. Dee et al. present an oxygen-isotope time series of fossil corals from the central tropical Pacific to investigate ENSO's response to large volcanic eruptions during the past millennium. They found a weak tendency for an El Niño–like response in the year after an eruption, but not one that was statistically significant. These results suggest that large volcanic events have not triggered a detectable response in ENSO over the past thousand years and that their impact is small relative to the degree of natural variability.

Science, this issue p. 1477

Abstract

The El Niño–Southern Oscillation (ENSO) shapes global climate patterns yet its sensitivity to external climate forcing remains uncertain. Modeling studies suggest that ENSO is sensitive to sulfate aerosol forcing associated with explosive volcanism but observational support for this effect remains ambiguous. Here, we used absolutely dated fossil corals from the central tropical Pacific to gauge ENSO’s response to large volcanic eruptions of the last millennium. Superposed epoch analysis reveals a weak tendency for an El Niño–like response in the year after an eruption, but this response is not statistically significant, nor does it appear after the outsized 1257 Samalas eruption. Our results suggest that those models showing a strong ENSO response to volcanic forcing may overestimate the size of the forced response relative to natural ENSO variability.

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