Fred’s idea. Within recorded history several very large volcanic eruptions have had big short-term effects on human history, usually by causing temporary “volcanic winters.” The eruption of Tambora in 1815 lowered global temperatures by 1 degree F and caused epidemics, famines, and riots. Krakatoa in 1883 also reduced global temperatures by about 1 degree F. Other volcanic eruptions in the last 100 years have killed tens of thousands of people including one in Columbia in 1985 that killed about 25,000.
We don’t have to use this topic to springboard into a discussion of climate change. But, it would be natural, IMO, because some people use big volcanic eruptions to argue, erroneously, that climate change will be self-correcting in the same way that volcanoes’ worst effects are gone within a short time period. But it’s different: greenhouse gases stay in the atmosphere for hundreds, even thousands of years and their impacts are more global and less predictable.
Basic background climate science sites include climateprogress.org and realclimate.org. The former has a lot of good basic info on the issue, such as this summarizing scientific consensus on the expected effects of global warming, and breaking developments. (Latest development: Did you know that the last six months have been the hottest 1/2 year ever recorded?
See you there!