Global warming and the Singularity

Last night I made a serious strategic error: I dared to suggest to some Less Wrongers that unFriendly transcendent AI was not the most pressing danger facing Humanity.

In particular, I made the following claims:

1. That runaway anthropogenic climate change, while unlikely to cause Humanity's extinction, was very likely (with a probability of the order of 70%) to cause tens of millions of deaths through war, famine, pestilence, etc. in my expected lifetime (so before about 2060).
2. That with a lower but still worryingly high probability (of the order of 10%) ACC could bring about the end of our current civilisation in the same time frame.
3. That should our current civilisation end, it would be hard-to-impossible to bootstrap a new one from its ashes.
4. That unFriendly AI, by contrast, has a much lower (<1%) chance of occurring before 2060, but that its consequences include Humanity's total extinction.

I'm a pessimist. I make no apology for this fact. But note that I'm actually less pessimistic in this regard than the Singularitarian Nick Bostrom, whose paper on existential risks lists runaway ACC among the "bangs" (total extinction risks) rather than the "crunches" (permanent end of industrial civilisation). Defending my numbers is complicated by the fact that they're all pulled out of thin air extremely ballpark estimates¹, but I'll ( give it a go. )