The CO2 isn't the problem, it's the sulfur gases. They basically do the opposite of CO2. When Krakatoa errupted, it lowered global temperatures by 0.5 C. It canceled summer and caused famines. When large volcanoes erupt they don't cause a climate catastrophe, they ARE the climate.

Anyway, here's a neat video so you're not just believing a stranger on the internet.

https://youtu.be/fXb02MQ78yQ?si=Wry3fzXxBHUZ_IIu

Not sure but I think you mean affect instead of effect. But what's funny is this is a rare instance where it works with either word.