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Carl Sagan’s predictions were really dire. Here’s a three paragraph TLDR of his specific predictions from his 1983 article that brought "Nuclear Winter" into th
by danielvf 9y ago
Carl Sagan’s predictions were really dire. Here’s a three paragraph TLDR of his specific predictions from his 1983 article that brought "Nuclear Winter" into the vocabulary:
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“Our baseline case, as in many other studies, was a 5000-megaton war with only a modest fraction of the yield (20 percent) expended on urban or industrial targets… In the baseline case, the amount of sunlight at the ground was reduced to… too dark for plants to make a living from photosynthesis.
“Land temperatures, except for narrow strips of coastline, dropped to minus 25 Celsius (minus 13 degrees Fahrenheit) and stayed below freezing for months -- even for a summer war... virtually all crops and farm animals, at least in the Northern Hemisphere, would be destroyed, as would most varieties of uncultivated or domesticated food supplies. Most of the human survivors would starve.
“But what if nuclear wars can be contained, and much less than 5000 megatons is detonated? Perhaps the greatest surprise in our work was that even small nuclear wars can have devastating climatic effects. We considered a war in which a mere 100 megatons were exploded, less than one percent of the world arsenals, and only in low-yield airbursts over cities. This scenario, we found, would ignite thousands of fires, and the smoke from these fires alone would be enough to generate an epoch of cold and dark almost as severe as in the 5000 megaton case. The threshold for what Richard Turco has called The Nuclear Winter is very low.
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I think the reason the Carl Sagan was widely panned afterwords is that the science was just plain bad. The scale of the predictions he made were so off the charts from almost forty years of previous nuclear experience, that he was obviously was wrong. He predicted essentially the end of the humanity from a mere 100 megatons of nuclear explosions, and yet twenty years before article, the Soviet Union had tested a 50 megaton bomb with no more than the usual local effects.
Using bad science to advance a public policy goal is exactly what got us to the current "distrust of science"
- vilhelm_s 9y agoTo be clear, the claim was not that 100 megatons themselves would cause climate change, but that 100 firestorms in cities would, and that a 1 Mt bomb would be enough to cause a firestorm (there was one in Hiroshima). It's not completely clear to me just how bad the science was; like the article says there is still a debate today, so it's not completely settled even now. Wikipedia has a lot of discussion. https://en.wikipedia.org/wiki/Nuclear_winter https://en.wikipedia.org/wiki/Nuclear_winter
- foobarian 9y agoMy problem with these predictions is that volcanic eruptions at these energy scales and with plenty of ash output occur with some frequency, and the effects are still not human extinction.
- RcouF1uZ4gsC 9y agoI think celebrity scientists propounding disaster scenarios that have actual poor scientific backing, is one of the reasons why there is still so much skepticism about global warming. It is kind of like the story of the "boy that cried wolf". Scientists have been warning about impending doom so many times in the past, and in general things have never been better for humans on a global scale now. People learned to disregard dire predictions. Now, when there is a real danger, people are skeptical.
- mc32 9y agoIt reminds me of Bill Nye, an ME who is presented as a scientist, but isn't much more a scientist than an amateur scientist. He's good for kids, but not someone adults should look to for science, given it's scriptwriters and producers putting forth the "science" with him as frontman.
- mikeash 9y agoWhat are these "so many times" that scientists have incorrectly been warning about impending doom? Nuclear winter might qualify, but given that it's merely the difference between "everyone dies" and "humanity survives, but civilization is wrecked and we really must ensure that this never happens," it doesn't seem huge. What else is there?
- FeepingCreature 9y agoY2K, ozone hole. I know that those "don't count", because they actually got addressed, but they still feed into an unfortunate perceptual pattern.
- mikeash 9y agoThat seems unfair... but since we're talking about how people perceive it, that doesn't make it wrong.
- RcouF1uZ4gsC 9y agoEhrlich and the whole overpopulation predictions, DDT would wipe out songbirds, the prediction we would run out of oil, a new ice age, ozone hole, the whole concept of the doomsday clock, and now the whole AI will wipe out humanity fear. Part of this blame falls on the media. It amplifies the "gloom and doom" voices because that is what sells.
- gonational 9y ago5,000 megatons would be enough to destroy every major and semi-major city on the planet, literally. There are 4,416 cities on the planet with 150k+ population. 10 100kt bombs are more than enough to destroy most cities on the planet, at least when you define "destroy" as "most everything is broken and/or on fire and most people are dead within 1 year's time". After your 10-nukes-per-city campaign, you've still got another 5,840 100kt bombs left in your 5,000 megaton budget to divide among the largest cities (NYC, Tokyo, Hong Kong, Tehran, etc.). I'm stating this because I don't think it's too useful to predict the secondary effects (nuclear winter, etc.) of a war so terrible that basically everyone on the planet would already be dead (from blast, fire, etc.) or dying within a year's time (radiation, starvation from infrastructure collapse, etc.).
- danielvf 9y agoI'm certainly not saying nuclear war wouldn't be awful - it would be! But in judging Carl Sagan's claims, we look at what he actually wrote to the public, and it's the specific climate claims that Carl Sagan made that appear to be wildly incorrect.
- goatlover 9y agoThe people not near the cities targeted wouldn't die from environmental results. That's the point. They might die from serious economic disruption if they can't get access to food. But there would be people who would survive it. There's quite a lot of land in flyover states and what not. A lot of that is farmland.
- greedo 9y agoA lot of that farmland you're referring to houses ICBM silos, command and control facilities, or airbases.
- goatlover 9y agoI'm guessing that's less than 0.01% of the actual land area. Anyway, there's mountains, forests, arctic wilderness, islands, etc. where some people live in various concentrations. Human civilization would take a massive blow from an all-out nuclear war, but human beings wouldn't go extinct, and some elements of civilization would remain. It's not like all technological capability or knowledge would be lost.
- arethuza 9y ago"Soviet Union had tested a 50 megaton bomb with no more than the usual local effects" The Tsar Bomba was tested over artic wildereness in Novaya Zemlya, not over a city.
- pc86 9y agoDo the effects on the climate change depending on whether it's over a city or the wilderness?
- arethuza 9y agoI believe the idea is that if you explode an H-bomb over a large city an awful lot of stuff is going to catch fire resulting in huge firestorms that would (along with the effects of the explosions themselves) raise a lot of stuff into the atmosphere. Of course, thankfully, we don't really know what would happen when a large city receives a realistic attack from multiple H-bombs.
- ghostcluster 9y agoExcept we know what happens when major cities are fire bombed from World War II, and we know the effects of the much worse 1991 Kuwait oil fires which caused no such effects.
- vilhelm_s 9y agoI think it's not quite so easy. There were many cities bombed in World War II (maybe 60 in Japan and additional ones in Germany), but there were only 5 or 6 firestorms. Similarly, the Kuwait oil fires created a lot of soot, but the plume is isolated to a given point, which causes it to disperse before reaching the stratosphere. The claim is that firestorms in particular would create climate change, because a single city-sized plume could carry the soot much higher than if the city burned and released the same amount of soot in an ordinary fire. https://en.wikipedia.org/wiki/Firestorm#City_firestorms https://en.wikipedia.org/wiki/Firestorm#City_firestorms https://en.wikipedia.org/wiki/Nuclear_winter https://en.wikipedia.org/wiki/Nuclear_winter
- ghostcluster 9y ago> Using bad science to advance a public policy goal is exactly what got us to the current "distrust of science" This is exactly it. And it is why both Google and the lion's share of the mainstream media's treatment of Damore's memo was so frustrating. Google especially, when anyone can look up the wealth of scientific literature through Google Scholar and see that decades of science back him up, including the papers he cited directly.