The underwater Hunga Tonga-Hunga Ha-apai (HT) volcano violently erupted in the early hours of 15th January 2022, and injected volcanic gases and aerosols up to over 50 km altitude. The peculiar phreato-magmatic nature of the HT eruption produced the largest perturbation of stratospheric water vapour observed in the satellite era. Despite the unprecedented explosivity of the eruption, it was initially suggested that the impact of HT on the stratospheric aerosol layer and climate is negligible (http://www.sparc-ssirc.org/downloads/VolRes_summary_of_the_Hunga-Vfinal.pdf). In contrast with these first estimations, we found that this event produced the largest global perturbation of stratospheric aerosols since the Pinatubo volcano eruption in 1991. We observed very fast sulphate aerosol formation due to the exceptionally large availability of water vapour for this event. 

The large stratospheric water vapour perturbation had also dramatic, unexpected effects on the radiative impacts for this event. Immediately after the eruption, water vapour radiative cooling dominated the local stratospheric heating/cooling rates and produced a spectacular fast descent of the plume.

Volcanic aerosol cooling dominated the radiative forcing during the first days after the eruption. However, after two weeks, due to dispersion/dilution, water vapour warming started to dominate the top-of-the-atmosphere radiative forcing, leading to a net warming of the climate system. A warming effect on the climate system has never been observed before for a volcanic eruption, which usually produce a transient cooling.

If interested in the full story of this unique climate-warming volcanic eruption --> https://www.nature.com/articles/s43247-022-00618-z