Proxy evidence for an El Nino-like response to volcanic forcing

Past studies have suggested a statistical connection between explosive volcanic eruptions and subsequent El Nino climate events(1,2). This connection, however, has remained controversial(3-5). Here we present support for a response of the El Nino/Southern Oscillation (ENSO) phenomenon(6,7) to forcing from explosive volcanism by using two different palaeoclimate reconstructions of El Nino activity(8,9) and two independent, proxy-based chronologies of explosive volcanic activity(5) from AD 1649 to the present. We demonstrate a significant, multi-year, El Nino-like response to explosive tropical volcanic forcing over the past several centuries. The results imply roughly a doubling of the probability of an El Nino event occurring in the winter following a volcanic eruption. Our empirical findings shed light on how the tropical Pacific ocean-atmosphere system may respond to exogenous (both natural and anthropogenic) radiative forcing.