To follow up on Tonga... based on this it seems like the effect would be pretty minor overall.
Volcanic eruption in Tonga recorded January 15, 2022 is likely to add to global warming and the depletion of Earth’s ozone layer, according to a new study.
The violent underwater eruption of Hunga Tonga-Hunga Ha’apai injected 146 teragrams (1 teragram equals a trillion grams) of water vapour into the stratosphere. The stratosphere is the layer of atmosphere between 10-50 kilometres above the surface of the Earth.
The water vapour, a greenhouse gas, released by the volcano, is roughly 10 per cent of the water already present in the stratosphere, noted the study published in Geophysical Letters July 1, 2022.
“Tonga eruption may be the first volcanic eruption observed to impact climate not through surface cooling caused by volcanic sulfate aerosols, but rather through surface warming caused by excess water vapour,” the study noted.