Dryland hydroclimatic variations have always been important priorities for scientific communities due to their fragile ecosystems, combined with limited socio-economic adaptation and mitigation capacity. Drylands show a drying response to global warming which can be attributed to internal variability and human activities^{1, 2}. Volcanic eruptions, as a significant natural external forcing, have been found to cause  a slowdown of the hydrological cycle. Furthermore, previous studies have paid more attention on the response of precipitation, runoff and potential evapotranspiration, not the surface water balance.

In this context, Shangrong Zhou and Fei Liu from Sun Yat-Sen University, Aiguo Dai from State University of New York, and Tianbao Zhao from Institute of Atmospheric Physics led a study exploring the hydroclimatic response to large tropical volcanic eruptions during the last millennium³.

This study investigated the hydroclimatic responses in global drylands to large tropical volcanic eruptions. We analyzed the Last Millennium simulations from 10 climate models that participated in the Paleoclimate Modeling Inter-comparison Projects (PMIPs) and the CESM Last Millennium Ensemble (CESM-LME) full forcing simulations. Additionally, we compared these findings with the hydroclimatic responses in the last millennium reconstructions and observation-derived data.

We demonstrated that large tropical volcanic eruptions can induce significant two-year hydroclimatic wetting over drylands by employing the multi-model ensemble mean. During this wetting period, several hydroclimatic indicators show significant positive anomalies over most drylands. The primary contribution to the wetting response is the potential evapotranspiration reduction resulting from dryland surface cooling and reduced solar radiation, as well as a weak contribution from increased precipitation.

This wetting response of drylands to volcanic eruptions also demonstrates some benefits over the global hydrological slowdown resulting from stratospheric aerosol injection, which replicates the cooling effects of volcanic eruptions to address global warming.

References:

1. Dai, A. Drought under global warming: a review. Wiley Interdiscip Rev Clim Change 2, 45-65 (2011a).
2. Dai, A. Hydroclimatic trends during 1950–2018 over global land. Climate Dyn 56, 4027-4049 (2021).
3.  Zhou, S., Liu F., Dai A., Zhao T. Dryland hydroclimatic response to large tropical volcanic eruptions during the last millennium. npj Clim Atmos Sci 7, 85 (2024).