This 1883 photograph shows the aftermath of the eruption of Krakatoa. The explosive force of a 200-megatonne bomb killed 36,000 people and cooled the entire Earth by an average of 0.6°C. The ensuing tsunami waves reached as high as 150 ft, rocking ships as far away as South Africa. via Reddit

Man can't do anything that mother nature can't do better. A couple of volcanic eruptions and we'll be in an ice age wondering how to heat up the planet (if the green folks maintain form). A super volcano like the beast in a certain national park here in the US and we'd be looking at a catastrophe that will change the course of human history.  The craziness is beginning to break though.  A group of scientist have stated that climate change is just modern hysteria.  For some reason this generation searches for shit to be scared of instead of just looking down the street and seeing the monsters walking amongst them.

Around noon on 27 August 1883, a rain of hot ash fell around Ketimbang (now Katibung in Lampung Province) in Sumatra. Approximately 1,000 people were killed in Sumatra; there were no survivors from the 3,000 people on the island of Sebesi. There are numerous reports of groups of human skeletons floating across the Indian Ocean on rafts of volcanic pumice and washing up on the east coast of Africa up to a year after the eruption
(Note.  This is NOT the largest eruption recorded in history)