Indeed. If you want to find out more, the best book that I've found on this subject is _Global Catastrophic Risks_, edited by Nick Bostrom and Milan M. Cirkovic:
"In Global Catastrophic Risks 25 leading experts look at the gravest risks facing humanity in the 21st century, including asteroid impacts, gamma-ray bursts, Earth-based natural catastrophes, nuclear war, terrorism, global warming, biological weapons, totalitarianism, advanced nanotechnology, general artificial intelligence, and social collapse. The book also addresses over-arching issues - policy responses and methods for predicting and managing catastrophes. "
http://www.amazon.com/Global-Catastrophic-Risks-Nick-Bostrom...
"In Global Catastrophic Risks 25 leading experts look at the gravest risks facing humanity in the 21st century, including asteroid impacts, gamma-ray bursts, Earth-based natural catastrophes, nuclear war, terrorism, global warming, biological weapons, totalitarianism, advanced nanotechnology, general artificial intelligence, and social collapse. The book also addresses over-arching issues - policy responses and methods for predicting and managing catastrophes. "