I also talked to some researchers who study existential risks, like John Halstead, who studies climate change mitigation at the philanthropic advising group Founders Pledge, and who has a detailed online analysis of all the (strikingly few) climate change papers that address existential risk (his analysis has not been peer-reviewed yet).
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Further, “the carbon effects don’t seem to pose an existential risk,” he told me. “People use 10 degrees as an illustrative example” — of a nightmare scenario where climate change goes much, much worse than expected in every respect — “and looking at it, even 10 degrees would not really cause the collapse of industrial civilization,” though the effects would still be pretty horrifying.
From Halstead’s report (which Vox seems to represent as a reliable meta-analysis—my apologies for butchering the formatting):
I FOCUS ONLY ON DIRECT RISKS AND DO NOT DISCUSS THE INDIRECT RISKS, SUCH AS WAR DUE TO MASS MIGRATION
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The big takeaway from looking at the literature on the impact of extreme warming is that the impact of >4 degrees is dramatically understudied. King et al characterise this as “knowing the most about what matters least”
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-Is extreme warming an ex risk?
*6 degrees
On the models: For the impacts I have looked at, 6 degrees isn’t plausibly an ex risk, though it would be very bad. 6 degrees would drastically change the face of the globe, with multi-metre sea level rises, massive coastal flooding, and the uninhabitability of the tropics.
*10 degrees
On the models: It’s hard to come up with ways that this could directly be an ex risk, though it would be extremely bad.
-Model uncertainty
The impacts of extreme warming are chronically understudied suggesting some model uncertainty.
There might be some unforeseen process which makes human civilisation difficult to sustain.
-Indirect risks
None of this considers the indirect risks, like mass migration and political conflict. These could be a pretty substantial risk over the next 150 years.
It sounds like study on the effects and consequences of extreme warming, particularly indirect/secondary risks, are quite neglected and could benefit from some more work (although I’m not sure how tractable work on this is at this point).
Note that the Vox article also doesn’t discuss existential risks arising from indirect effects.
From the Vox article:
From Halstead’s report (which Vox seems to represent as a reliable meta-analysis—my apologies for butchering the formatting):
It sounds like study on the effects and consequences of extreme warming, particularly indirect/secondary risks, are quite neglected and could benefit from some more work (although I’m not sure how tractable work on this is at this point).
Note that the Vox article also doesn’t discuss existential risks arising from indirect effects.