Global hydroclimatic response to tropical volcanic eruptions over the last millennium

Large tropical volcanic eruptions can affect the climate of many regions on Earth, yet it is uncertain how the largest eruptions over the past millennium may have altered Earth's hydroclimate. Here, we analyze the global hydroclimatic response to all the tropical volcanic eruptions over the past millennium that were larger than the Mount Pinatubo eruption of 1991. Using the Paleo Hydrodynamics Data Assimilation product (PHYDA), we find that these large volcanic eruptions tended to produce dry conditions over tropical Africa, Central Asia and the Middle East and wet conditions over much of Oceania and the South American monsoon region. These anomalies are statistically significant, and they persisted for more than a decade in some regions. The persistence of the anomalies is associated with southward shifts in the Intertropical Convergence Zone and sea surface temperature changes in the Pacific and Atlantic oceans. We compare the PHYDA results with the stand-alone model response of the Community Earth System Model (CESM)-Last Millennium Ensemble. We find that the proxy-constrained PHYDA estimates are larger and more persistent than the responses simulated by CESM. Understanding which of these estimates is more realistic is critical for accurately characterizing the hydroclimate risks of future volcanic eruptions.

Automated summary

Large tropical volcanic eruptions can have a significant impact on global climate, leading to dry or wet conditions in different regions that can persist for over a decade. The southward shift of the Intertropical Convergence Zone and changes in sea surface temperatures in the Pacific and Atlantic oceans are associated with these climate anomalies. The proxy-constrained PHYDA estimates show larger and more persistent responses compared to simulations by the CESM model, highlighting the importance of determining which estimates are more realistic for accurately assessing the hydroclimate risks of future volcanic eruptions.