You misunderstood. I mentioned the zombie outbreak as one of the possible things that could happen in relation to asking if scientists should write an open letter about every possible disaster. Obviously climate collapse is more likely, but what about asteroid impacts? Why aren't we building preventative measures against that?

Honestly, the most likely thing to cause mass death and civlisational collapse is 1) nuclear war, ironically supported by the same liberals who talk about global warming, IPCC, etc. 2) a deadly virus that develops in the cramped conditions global capitalism forces people to live in.