Up to the eruption of Mount St Helens the major effect of volcanic blow outs on the transparency of the atmosphere was down to dust produced by fine ash particles blasted into the sky. See for example, Lamb in 1972. This led to the concept that only large eruptions capable of blasting tephra into the stratosphere would produce a climatic effect – such as an opaque sky. After research following Mount St Helens, a game changer, it became clear that it was mostly small droplets of saturated sulphuric acid converted from volcanic sulphur dioxide that had a suffiently long half life in the atmosphere to be climatically important. At that time it was also established that sulphuric acid droplets in the Jonge Layer had a very small absorption to backscatter ratio and these always produced cooling. In other words, some large volcanoes contributed little to global cooling but some much smaller volcanoes could have done.
Hence, we now have a lot of graphs that seek to show every cold downturn in temperature has a volcanic origin. Is that entirely true? We know that the atmospheric meteor explosion that was responsible for the demise of the cities on the Plain, purported to be Biblical Sodom and its satellite towns, released a large amount of sulphur rich particles and gave rise to the Biblical description of fire and brimstone. The latter = sulphur. Whether or not Tall al-Hammam was Sodom or not is immaterial. The archaeology demonstrates that sulphur arose from the meteor explosion in the lower atmosphere. It stands to reason similar meteor explosions in the lower atmosphere were also capable of generating cool weather – and they may have been responsible for longer bouts of climate change. Meteor explosions in combination with volcanic eruptions, the one triggering the other, are also a possibility in a catastrophist view of the past.