EA - Nuclear winter scepticism by Vasco Grilo

Welcome to The Nonlinear Library, where we use Text-to-Speech software to convert the best writing from the Rationalist and EA communities into audio. This is: Nuclear winter scepticism, published by Vasco Grilo on August 13, 2023 on The Effective Altruism Forum.This is a crosspost for Nuclear Winter by Bean from Naval Gazing, published on 24 April 2022. It argues Toon 2008 has overestimated the soot ejected into the stratosphere following a nuclear war by something like a factor of 191 (= 1.522(1 + 2)/2(2 + 3)/2(4 + 13)/2). I have not investigated the claims made in Bean's post, but that seems worthwhile. If its conclusions hold, the soot ejected into the stratosphere following the 4.4 k nuclear detonations analysed in Toon 2008 would be 0.942 Tg (= 180/191) instead of "180 Tg". From Fig. 3a of Toon 2014, the lower soot ejection would lead to a reduction in temperature of 0.2 ºC, and in precipitation of 0.6 %. These would have a negligible impact in terms of food security, and imply the deaths from the climatic effects being dwarfed by the "770 million [direct] casualties" mentioned in Toon 2008.For context, Luísa Rodriguez estimated "30 Tg" of soot would be ejected into the stratosphere in a nuclear war between the United States and Russia. Nevertheless, Luísa notes the following:As a final point, I'd like to emphasize that the nuclear winter is quite controversial (for example, see: Singer, 1985; Seitz, 2011; Robock, 2011; Coupe et al., 2019; Reisner et al., 2019; Pausata et al., 2016; Reisner et al., 2018; Also see the summary of the nuclear winter controversy in Wikipedia's article on nuclear winter). Critics argue that the parameters fed into the climate models (like, how much smoke would be generated by a given exchange) as well as the assumptions in the climate models themselves (for example, the way clouds would behave) are suspect, and may have been biased by the researchers' political motivations (for example, see: Singer, 1985; Seitz, 2011; Reisner et al., 2019; Pausata et al., 2016; Reisner et al., 2018). I take these criticisms very seriously - and believe we should probably be skeptical of this body of research as a result. For the purposes of this estimation, I assume that the nuclear winter research comes to the right conclusion.However, if we discounted the expected harm caused by US-Russia nuclear war for the fact that the nuclear winter hypothesis is somewhat suspect, the expected harm could shrink substantially.As Luísa, I have been assuming "the nuclear winter research comes to the right conclusion", but I suppose it is worth bringing more attention to potential concerns. I have also not flagged them in my posts, so I am crossposting Bean's analysis for some balance.Nuclear WinterWhen I took a broad overview of how destructive nuclear weapons are, one of the areas I looked at was nuclear winter, but I only dealt with it briefly. As such, it was something worth circling back to for a more in-depth look at the science involved.First, as my opponent here, I'm going to take What the science says: Could humans survive a nuclear war between NATO and Russia? from the prestigious-sounding "Alliance For Science", affiliated with Cornell University, and the papers it cites in hopes of being fair to the other side. Things don't start off well, as they claim that we're closer to nuclear war than any time since the Cuban Missile Crisis, which is clearly nonsense given Able Archer 83 among others. This is followed with the following gem: "Many scientists have investigated this question already. Their work is surprisingly little known, likely because in peacetime no one wants to think the unthinkable. But we are no longer in peacetime and the shadows of multiple mushroom clouds are looming once again over our planet." Clearly, I must have hallucinated the big PR push around nuclear winter back in the mid-80s. Well, I didn't because I wasn't born yet, but everyone else must have.Things don't get much better. ...