From Myhrvold at Bloomy:
None of these catastrophes came entirely out of the blue. To the contrary, geologic history tells us that we’ve actually gotten off lucky. In 1783, the Laki volcano in Iceland erupted so violently that it killed perhaps a quarter of the country’s population. That volcano put enough ash into the sky to change the weather in the entire Northern Hemisphere, causing crop failures and famines across Europe, India, Japan, Egypt and North America that pushed the total death toll to 6 million. It took almost a decade for the weather to recover.
Laki isn’t even the worst Icelandic volcano on record — far larger was the six-year eruption of Eldgja that began in 934.
One could recount many such examples, but people’s eyes tend to glaze over when you talk about something that last occurred in 1783, much less 934. Surely things are different now, they say. The unfortunate truth is quite the opposite — a millennium ago was yesterday as far as the Earth is concerned, and the relevant phenomena operate as vigorously as ever. Proud as we are of the many technological achievements of modern society, we are actually more vulnerable than ever because we live more densely, within a complex and sometimes fragile web of buildings, roads, bridges and the like.