I host “The Precipice” reading groups for EA Virtual. One participant asked how nuclear winter models have evolved such that nuclear winter is now predicted to be much longer. Ord states that nuclear winter models have changed significantly from the original, though the basic mechanism is the same. He stated that the details were to conplex too go into in the book. Could someone give me a source or explain how exactly nuclear winter models have evolved to be more complex and predict longer nuclear winter?

Edit: this is not a question about how a nuclear war would play out, it is specifically about the mechanism of how nuclear winter would occur, which Ord states has evolved away from and become more complex than smoke blocking out the sun, though in essence it is similar.




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I think nuclear winters are now predicted to be much less severe than once feared. At least, that is what a very indepth EA forum post argues.

I think the finding points us toward being a bit more skeptical of the idea that some effective altruists seem to hold — that a nuclear war between the US and Russia would necessarily lead to a nuclear winter that posed a large risk of extinction.

There is a lot of uncertainty of how much smoke would be produced and make it to the stratosphere (the post you refer to and my paper). But what I think the OP is referring to is the time that the smoke remains in the stratosphere. This was only about one year in the 1980s models, but now it's around 10 years. My understanding is that this is because the modern models take into account the fact that the sun hitting the smoke would warm it and therefore loft it higher in the stratosphere, meaning it would take longer to settle out.

Jordan Arel
Ah yes, I think this was what was referred to in the book. Thank you!