
Carl Sagan Warned the World About Nuclear Winter - anarbadalov
https://www.smithsonianmag.com/science-nature/when-carl-sagan-warned-world-about-nuclear-winter-180967198/?no-ist
======
quotemstr
The concept of "nuclear winter" is a great example of science gone wrong. As
it turns out, the original 1980s report vastly overestimated the amount of
combustible fuel in cities and inaccurately estimated both modern nuclear
weapon yield and blast size. Nuclear war would _not_ create firestorms capable
of injecting soot into the stratosphere and would _not_ cause years-long crop
failures. Nuclear war is, in fact, quite survivable.

[https://skeptoid.com/episodes/4244](https://skeptoid.com/episodes/4244)

[https://www.nature.com/articles/475037b](https://www.nature.com/articles/475037b)

[https://www.quora.com/How-many-nukes-would-it-take-to-
cause-...](https://www.quora.com/How-many-nukes-would-it-take-to-cause-a-
minor-nuclear-winter-What-about-a-moderate-one/answer/Allen-E-Hall-2)

~~~
knz
> Nuclear war is, in fact, quite survivable.

Nuclear winter may be less plausible than people believe but I'm not sure a
nuclear war can be described as "quite survivable". The potential disruption
to transportation networks that are essential for food distribution and
delivery of medical supplies etc would be catastrophic in a nuclear _war_. I
have no doubt that a nuclear exchange would be accompanied by electronic
warfare - disruption/destruction of the power grid in the north could kill
millions in the winter, especially if the petroleum supplies required to
evacuate were also disrupted.

~~~
mikeash
It depends on what exactly is meant by "quite survivable."

Does that mean you'll have a 99% chance to survive even if you do any special
preparation? If so, nuclear war definitely does not qualify.

Does it mean you'll have a greater than 50% chance to survive with good
preparation? Nuclear war probably qualifies.

Or does it just mean that nuclear war won't result in human extinction?
Nuclear war definitely qualifies.

An all-out nuclear war would definitely kill tens of millions immediately, and
tens if not hundreds of millions with the after-effects. You may not see
years-long crop failures due to nuclear winter, but you'll get the same
ultimate effect from lack of fertilizer, machinery, and distribution
infrastructure. And fallout. A good chunk of the US's productive agricultural
land is downwind from ICBM sites which would be targeted for extremely dirty
ground burst attacks.

~~~
pvg
There's no reasonable interpretation of a 50%-ish survival rate that can be
described as 'quite survivable'. Toxicologists say LD50, for instance, not
QS50.

~~~
khedoros1
On an individual scale? Sure. On a civilization or species scale? Survival of
the larger group is almost certain if each individual has "only" a 50% chance
of death.

~~~
quotemstr
The Black Death, after all, killed about half of Europe's population. European
civilization survived.

~~~
ekianjo
Was it really half? I have seen figures around 30%. Are there any accurate
records in every country at the time?

------
danielvf
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:

—

“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.

—

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"

~~~
gonational
5,000 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.).

~~~
jabretti
That sounds like a city-dweller's perspective.

Sure, I would almost certainly be dead, but life on Earth would continue, our
species would continue, and our civilisation would continue (albeit with some
major setbacks).

Besides, I don't think anyone's nuclear war plan is actually to destroy every
major to semi-major city on Earth. In a realistic 1980s nuclear war, a lot of
nukes would be targeted at military bases and the like. Plenty of others would
destroy every major city in the US and USSR, plus each country's nuclear-armed
allies. Maybe we here in Australia would get a nuke or two out of spite. But
is anyone going to bother to nuke South America?

~~~
ekianjo
> In a realistic 1980s nuclear war, a lot of nukes would be targeted at
> military bases and the like

i think it's mentioned in Command and Control (book) but if I recall correctly
the plan from the US perspective was not only to nuke military targets, but
also all major population centers, with several thermonuclear bombs for each
target, for good measure. And that was not only the USSR, but basically every
ally of the USSR as well.

You can imagine that the other side was also going to do about the same thing.

Sure, some countries may have been relatively spared, but all in all the whole
of Europe, US, Russia, China, would have been annihilated.

------
mcguire
I find it weird that scientists get crap from other scientists for speaking
publicly. Simple jealousy doesn't explain the vehemence.

As for the politics of the issue, mutual assured destruction has been the
working theory since Eisenhower. Those who think strategic nuclear war is
winnable, as well as the SDI nutters, are threats to that stability.

~~~
Xeoncross
> Simple jealousy doesn't explain the vehemence.

In any industry, if you attack/speak-against my beliefs/views/plans/theories,
then I don't like it. Even if you didn't mean too. Even if you didn't know I
existed or had those views.

It's not about science, it's about humans defending their worldview and
beliefs. Even stamp collecting has this.

Anything people put time/effort into has this.

edit: ChuckMcM does a better job describing this.

~~~
ethbro
Aka

[https://en.m.wikipedia.org/wiki/Escalation_of_commitment](https://en.m.wikipedia.org/wiki/Escalation_of_commitment)

[https://en.m.wikipedia.org/wiki/Confirmation_bias](https://en.m.wikipedia.org/wiki/Confirmation_bias)

[https://en.m.wikipedia.org/wiki/Cognitive_dissonance](https://en.m.wikipedia.org/wiki/Cognitive_dissonance)

------
Robotbeat
I think it's worth pointing out that the global nuclear arsenal today is about
a fifth the size it was when Carl Sagan made this warning. We've made
significant progress toward reducing existential risk.
[https://en.wikipedia.org/wiki/List_of_states_with_nuclear_we...](https://en.wikipedia.org/wiki/List_of_states_with_nuclear_weapons#/media/File:US_and_USSR_nuclear_stockpiles.svg)

~~~
thrillgore
It's a fifth of what it was, but yet the ordinance (and "migratory" patterns
of civilization to cities/shrinking factory towns, globalized economy) is
enough to decimate the population dozens of times over; and suspend modern
civilization.

------
dpflan
This article is interesting; I would say that it is crucial that such warnings
and such "celebrity" scientists enter the public debate (expecting backlash
and support and discussion - is this not similar to sharing research within
one's academic community?). The public can have their existential dread
soothed by the idea of nuclear weapons as defense, but it seems that their
understanding of their usage is not sufficient. Sagan or someone needed to
provide thoughtful discourse on the repercussions of using the weapon. It does
seem great to think your nation can use this powerful tool to attack /
ultimately defend its and your existence, but the power of and nature of the
weapon requires understanding it. The scale of the weapon is not
comprehensible, as much as say a simpler explosive device could be to
layperson (voter?).

The advocates of SDI and nuclear did not seem to discuss the repercussions of
use, rather the fact that the power is a deterrent and useful against enemies.
The repercussions are what limit the use of nuclear as a strategic weapon.

Excerpt from the article: '“People didn’t want to change the way they were
thinking of [nuclear] weapons,” he says. “I see an echo of that now. What
nuclear winter shows is that they’re not really weapons in the sense that
other things are weapons: that you can use them to harm your adversary without
harming yourself. People are not really considering that if there really were
to be a nuclear conflagration, in addition to how unthinkably horrible it
would be in the direct theater of the use of those weapons—say in the Korean
peninsula and surrounding areas—there would also be global effects.”' \-
Grinspoon

~~~
ghostcluster
The absolutely incorrect thing to do is to lie to the public by using your
credibility as a scientist to knowingly make up your own incorrect story about
the hypothetical effects.

You wonder why so many people don't trust "scientists" when you can see they
are clearly lying to push a social cause?

~~~
dpflan
I agree. That is a true failure that has effects on all future scientists
going public. Presenting hypothetical effects as a possibility and open to
discussion / discourse is still important.

------
augustocallejas
A great mini-doc overview of the same topic:

[https://www.retroreport.org/video/nuclear-
winter/](https://www.retroreport.org/video/nuclear-winter/)

~~~
rounce
Also, the 1984 BBC documentary 'On the 8th Day' is worth a look:
[https://www.youtube.com/watch?v=tCz9zqTTark](https://www.youtube.com/watch?v=tCz9zqTTark)

~~~
ghostcluster
How about this NYTimes story where even the scientist who coined the term
disavowed it as a scenario.

> the five scientists who introduced the term ''nuclear winter'' now
> acknowledge that they overestimated its severity, and their concession
> appears to have moderated the longstanding debate.

> most discounted the extreme view that global chilling of the atmosphere
> would be severe enough to be described as ''winter.'' Scientists
> specializing in such studies also generally reject the suggestion that a
> ''nuclear winter,'' in itself, could bring about the extinction of the human
> race. Even Dr. Richard P. Turco, the physicist who coined the phrase
> ''nuclear winter,'' discounts the idea.

[http://www.nytimes.com/1990/01/23/science/nuclear-winter-
the...](http://www.nytimes.com/1990/01/23/science/nuclear-winter-theorists-
pull-back.html?pagewanted=all)

------
Lendal
Was Carl Sagan aware of just how many nuclear weapons had already been
detonated in testing by both countries, as well as by India and China? I don't
know the exact number but I do know it's over a hundred. If his models were
correct, we'd have already been experiencing a nuclear winter by the 1980's.

~~~
toss1
Um, no. The tests were rather deliberately located away from cities and
avoided creating the firestorms required to raise the massive dust clouds and
create the effect. They were also not near-simultaneous.

------
downrightmike
You probably don't need a high yield if you just nuke a volcano or super
volcano
[https://en.wikipedia.org/wiki/Volcanic_winter](https://en.wikipedia.org/wiki/Volcanic_winter)

------
wallflower
"I do not know with what weapons World War III will be fought, but World War
IV will be fought with sticks and stones!" ~Albert Einstein

------
bayesian_horse
Winter is coming!

Sorry, couldn't resist.

------
marcoperaza
Worries about nuclear fallout are vastly overstated. If you detonate the
weapons at the right altitude, they retain most of their destructive effect
without creating long term catastrophic fallout.

~~~
knowaveragejoe
Surely that will be considered when employing these weapons in a war.

~~~
kazagistar
Surely the "when" was meant to be an "if"? Is the default assumption that this
level of violence will happen again? The presence of that mindset is what
allows escalation, rather then it being considered at most a crazy edge case
scenario.

My coworkers were discussing what would happen if California voted to declare
independence from the United States. The hypothetical scenario instantly moved
to "occupation by US Military forces", which hadn't even come up in my mind.
Its not like the EU states moved to occupy Britain or anything. It seems like
the obvious solution is to try to sit down, think about it, debate it, and
work out the problems of the involved parties. Why turn directly to violence?

~~~
marcoperaza
> _The hypothetical scenario instantly moved to "occupation by US Military
> forces", which hadn't even come up in my mind. Its not like the EU states
> moved to occupy Britain or anything._

We had a war about this. US states are not allowed to secede. The Union is
perpetual.

~~~
marcoperaza
And in contrast, the EU explicitly allows exit. So it’s not a very good
comparison.

