I've finished the Bostrom-Cirkovic edited volume on Global Catastrophic Risks. The book is a fun read, but it ultimately failed to scare me - and I'm the author of one of the chapters! Out of a long list of conceivable horrors - everything from asteroids and super-vulcanism to AI and nanotech - the only threat that gives me pause is nuclear war. As for the rest, it's not clear that any of them are a greater threat to my life or yours than airplane travel.
I don't mean to say that these risks aren't worth thinking about. If you use a standard $10M/life value, then the expected cost of exposing seven billion people to a one-in-a-million lifetime risk is $70B. If a book chapter has a one-in-a-million chance of eliminating that risk, that's a $70,000 piece of scholarship - not bad for a couple months' research. Nevertheless, no sensible person loses sleep over a one-in-a-million lifetime threat to his own life, or the lives of the people he cares about. Life's too short.
How seriously do I take the possibility that a world totalitarian government will emerge during the next one thousand years and last for a thousand years or more? Despite the complexity and guesswork inherent in answering this question, I will hazard a response. My unconditional probability – i.e., the probability I assign given all the information I now have - is 5%.
In fact, I argue that people who turn to world government to handle "global catastrophic risks" could easily be paving the way for the greater threat of totalitarianism:
But one of the main lessons of the history of totalitarianism is that moderation and inaction are underrated. Few problems turned out to be as "intolerable" as they seemed to people at the time, and many “problems” were better than the alternative. Countries that "did nothing" about poverty during the twentieth century frequently became rich through gradual economic growth. Countries that waged "total war" on poverty frequently not only choked off economic growth, but starved.
Along these lines, one particularly scary scenario for the future is that overblown doomsday worries become the rationale for world government, paving the way for an unanticipated global catastrophe: totalitarianism. Those who call for the countries of the world to unite against threats to humanity should consider the possibility that unification itself is the greater threat.
Nevertheless, I've never lost a night's sleep over the possibility that crusades against global warming and asteroids will end in totalitarianism. From a world-historic perspective, this scenario is worth thinking about. But if my chapter makes you fear for your future, even I'd say you're taking me too seriously.