Tipler doesn’t give a quantitative estimate, so maybe that shouldn’t count.
Leslie and Bostrom’s estimates themselves are arguably less pessimistic than Rees, in the sense that their lower bounds for the risk level are lower
But I include their estimates here anyway since it’s possible that their overall distribution would be more pessimistic, and because Rees’ estimate is not necessarily about existential catastrophe (since it could include other ways in which “our present civilisation” doesn’t “survive”)
Leslie and Bostrom’s estimates aren’t as near-term as Rees’ estimate
So Tarsney’s claim is reasonable on this front; I’m just adding some extra info.
There are also some more pessimistic estimates in sources that aren’t academic but do seem similarly worth paying attention to to Rees’ estimate; see my database.
tl;dr I’m aware of 1-3 other things that might count as more pessimistic estimates of near-term existential risk in the academic literature.
Specifically:
Frank Tipler wrote “Personally, I now think we humans will be wiped out this century”
John Leslie estimated the risk of extinction over the next five centuries as at or above 30%.
Nick Bostrom estimates the odds that “existential disaster will do us in” at some point as probably at or above 25%.
For further details and sources, see my Database of existential risk estimates (or similar) (see here for the accompanying post).
But:
Tipler doesn’t give a quantitative estimate, so maybe that shouldn’t count.
Leslie and Bostrom’s estimates themselves are arguably less pessimistic than Rees, in the sense that their lower bounds for the risk level are lower
But I include their estimates here anyway since it’s possible that their overall distribution would be more pessimistic, and because Rees’ estimate is not necessarily about existential catastrophe (since it could include other ways in which “our present civilisation” doesn’t “survive”)
Leslie and Bostrom’s estimates aren’t as near-term as Rees’ estimate
So Tarsney’s claim is reasonable on this front; I’m just adding some extra info.
There are also some more pessimistic estimates in sources that aren’t academic but do seem similarly worth paying attention to to Rees’ estimate; see my database.