Volcanic eruptions inject vast amounts of aerosols into the stratosphere, driving well-known cooling effects by scattering solar radiation. However, their role in modulating stratospheric water vapor—a potent greenhouse gas—has been largely overlooked. In this talk, I present results from simulations of a Pinatubo-like explosive tropical eruption, revealing that aerosol heating significantly enhances the entry of water vapor into the stratosphere. This moistening effect is further amplified one year after the eruption due to aerosol-radiation-dynamical feedbacks, a process that has likely been underestimated in previous assessments.
These findings have critical implications for our understanding of volcanic climate forcing and stratospheric aerosol injection (SAI) geoengineering. While SAI is often considered a cooling strategy, the associated increase in stratospheric water vapor could partially offset its intended effects, introducing complex feedbacks that must be accounted for in climate models. By reassessing the interplay between aerosols, water vapor, and climate dynamics, this study highlights the need for a more comprehensive evaluation of both natural and anthropogenic stratospheric perturbations.
 

stratospheric aerosols,stratospheric water vapour,aerosol-radiation-dynamic feedback