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[Music]
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Thanks for the warm welcome. But I'm
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here to tell you about something
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terrible. But you have to know about
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this problem because then we can solve
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it together. Here's our beautiful
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planet. But after a nuclear war, it
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might look like this with smoke covering
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the planet, blocking out the sun, and
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making it cold and dark at the Earth's
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surface. And this would produce a
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nuclear winter. That is, the
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temperatures would get below freezing
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even in the summertime, which would kill
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all the crops and produce a global
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famine. We discovered this working in
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the 1980s. This is the most important
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work I've ever done as a as a climate
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scientist. And what the the good news
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about that that this could be produced
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is that this helped to change the world.
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Here's a graph showing the number of
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nuclear weapons on the planet. And there
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used to be zero, then there were two,
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then the US started the first nuclear
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war, then there were zero, and then the
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number started going up. And the US
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number went up and the Russians cut up.
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And in the 1980s, there were 70,000
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nuclear weapons on the planet. The arms
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race was going crazy. And this research
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came out and it was done jointly by
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Russian and American scientists getting
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the same results. And so it couldn't be
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considered propaganda from one side or
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the other. And I published a paper the
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next year uh and
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uh whoops and then the Soviet Union
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ended five years later. So people say
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why did the arms race end? It wasn't
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because the Soviet Union ended. Maybe
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part of it was because of demonstrations
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or the Soviet Union was running out of
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money, but there was really a lot of
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controversy about this nuclear winter
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research and people started realizing
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how horrible the direct effects of
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nuclear war would be and then arms race
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ended. And why do I tell you that it was
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because of nuclear winter? Because you
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can ask the person that made the
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decision. Mikuel Gorbachoff was
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interviewed in in the year 2000 and he
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said, you know, models made by Russian
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and American scientists showed that a
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nuclear war would result in a nuclear
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winter that would be extremely
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destructive to all life on Earth. The
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knowledge of that was a great stimulus
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to us to people of honor morality to act
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in that
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situation. So you might think, okay, the
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problem solved. The number of weapons
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are going down. But actually, the number
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of countries with weapons is going up.
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It used to be one country every five
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years would would have nuclear weapons.
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The Soviet Union ended, there were some
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countries that had them and didn't want
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them and gave them back. But then
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Pakistan and North Korea got them. There
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are nine countries now with nuclear
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weapons. And even though it's going
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down, there's still a lot of them on the
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planet. The US and Russia each have
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about 10,000. And the other countries
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with them have chosen to stop at 100 or
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200.
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How many nuclear weapons do you have to
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drop on the capital of your enemy in
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order for to deter them from attacking
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you?
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One. That's correct. Maybe you need two
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in case the first one doesn't doesn't
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work. So why do you need thousands of
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them? These other countries figure a
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couple hundred is more than enough. But
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it also brings up the question, what
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would happen if they fought a nuclear
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war? Now there's 32 more countries that
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could build them if they wanted to. they
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have the uranium or plutonium that they
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need that it's not a secret how to do
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it, but they've chosen not to. So, what
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happens when there's a nuclear weapon?
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When it goes off, it's like bringing a
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piece of the sun to the surface of the
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earth for a fraction of a second. It's
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so bright, everything nearby catches on
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fire, bursts into flames. And it's the
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smoke from the fires that would go up in
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the atmosphere and block out the sun and
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stay for for almost for more than a
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decade that would cause the effects of
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nuclear war. more people in countries
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that didn't have bombs dropped on them
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would die than people in where the bombs
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had the direct effects. Now, here's a
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photo uh drawing done by one of the
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survivors of Hiroshima. And what they
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remember is the fires. And this is what
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Hiroshima looked like afterwards. There
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were no no more buildings. They all went
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up in flames. And here's a uh cartoon of
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what some of these plumes of smoke might
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look like after a nuclear war started.
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So uh seven years ago at a conference
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Brian Ton and Rich Turko the people that
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invented the term nuclear winter told me
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that somebody asked them what would
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happen if India and Pakistan fought a
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nuclear war. They've each got about 100
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nuclear weapons and we calculated how
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much smoke you would get from the fires
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and it turns out it would be quite a
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bit. It would be 5 million tons of
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smoke. Imagine along the Kashmir border
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there's some uh Russ uh ind Indian
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soldier there and and a Pakistani
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soldier and they get in some sort of
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disagreement and it just goes out of
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control and because of fear or panic or
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miscommunication it develops into a
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nuclear war. So I said to them I said
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that's interesting who's going to
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calculate the climate response to that 5
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million tons of smoke. They said well we
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thought maybe you
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would. And I had a student Luke Oman who
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was ready to do that. He was studying
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volcanic eruptions and climate. So
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that's what we did. We s asked what
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would happen if a hundred uh nuclear
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bombs were dropped in India and Pakistan
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on targets that would produce smoke.
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This is much less than 1% of the current
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nuclear arsenal. We use these very small
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Hiroshimaized bombs because that's what
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we know are the easiest to make. It
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would be a horrible 20 million people
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would die from the direct effects of the
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blast, the reactivity, and the fires.
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But it would produce this 5 million tons
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of smoke. So, we put it into a climate
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model, the same ones we used to
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calculate global warming, effects of
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volcanic eruptions. And here's a movie
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showing what would happen. Uh, the smoke
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is coming out and spreading around the
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world. And this is the vertical
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distribution. So, this is the tropopause
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beneath here. There's rain to wash it
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out, but it gets heated by the sun. It's
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black and lofted up into the upper
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atmosphere into the stratosphere where
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it would stay, we discovered, for more
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than a decade. We were surprised how
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long it would stay. So uh then we looked
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at what would be the effects of this on
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the climate. So we did a calc in our
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model. We looked at the uh climate
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response. This is a graph of the global
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average temperature. The global warming
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that we're quite concerned about rightly
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so. If this smoke went in the
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atmosphere, it would rapidly plummet the
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temperatures to below little ice age
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changes. Now first of all, this is not a
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solution to global warming. uh uh that
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that's called geoengineering and people
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have proposed putting a a layer of
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particles like volcanoes do and that
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wouldn't kill anybody. It's still not a
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good idea but uh this would produce
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climate change unprecedented in recorded
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human history and it would uh
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uh get temperatures below what it was in
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the little ice age. So we said what
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would happen then to the crops. So, we
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took temperature and precipitation and
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sunlight changes and put it into a model
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that calculates crop productivity.
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Here's an example. In China, the crop
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productivity in China for rice would get
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25% below the normal, which is the black
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line for five years and even 20% for
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another five years. This would be this
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means China would only grow the amount
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of rice that they had when they had 300
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million fewer people than they have now.
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And the same thing would happen in other
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places. We did calculations in the
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United States. And here's a table of
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some of our results. Uh corn production
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in the US, so production 10 or 15% 20%
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below normal for a decade. This would be
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a global food crisis. Pe people trade
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food around the world. Remember a couple
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years ago there were these fires and
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drought in Russia. Uh got very hot in
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Moscow. They stopped exporting wheat
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because it affected their wheat crop. So
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people would stop trading. rich
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countries might be able to do okay, but
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countries that depend on imported food
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would have huge problems. And if they
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knew that this effect was going to
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happen, it would really be a global
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panic. Now, there's about a billion
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people now that have chronic
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malnutrition. And so they might really
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be severely affected and maybe uh two
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billion people might be dead from
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starvation from a nuclear war fought
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around the other side of the world
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between India and Pakistan with a tiny
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fraction of our current arsenal because
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the smoke would cover the world and stay
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there for a long
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time. Ira Helland a colleague of mine
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wrote an article about this. He called
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it nuclear famine. And he was able to
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show this report to Mikuel Gorbachoff
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last year. And Gorbachoff said, "I'm
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convinced that nuclear weapons must be
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abolished. Their use in military
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conflict is unthinkable. Using them to
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achieve political objectives is
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immoral." Over 25 years ago, President
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Reagan and I ended our summit meeting in
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Geneva with a joint statement that
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nuclear war cannot be won and must never
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be fought. And this new study
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underscores in stunning and det
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disturbing detail why this is the
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case. But it's a lot worse than
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that. This is a US Trident submarine. It
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has about a 100 nuclear weapons, much
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bigger than the ones we use in this
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simulation. Maybe a thousand Hiroshima
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on each submarine. And the US has 14 of
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them. And that's less than half of our
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arsenal. and the Russians have a have an
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arsenal about the same
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size. So we went back and said what
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would be the effects on climate if the
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US and Russia had a war today with the
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current arsenals and this would produce
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a much larger cloud of smoke causing
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much larger climate change and it could
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still produce nuclear winter today. You
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could still bring temperatures below
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freezing in the summertime and there
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would be no agriculture around the
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world. And we calculated what would
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happen to the globe. And the I and now I
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had to rescale the the figure. The red
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line is what I showed you before. The
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green and brown are what would happen
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for not 5 million tons but 50 million
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tons or 150 million tons of smoke which
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is still possible today. It would indeed
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be a little ice age. It would be a
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tragedy for the entire
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planet. What I've been telling you about
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so far is theory. It's calculations done
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with a climate model. We don't actually
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want to test this in the real
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world. So, how can we tell if it's
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right? We look at analoges. We look at
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things that have happened that can
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inform us about it, such as nighttime.
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When it gets nighttime, it gets cold and
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and and and or the seasonal cycles,
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which gave the name to it, nuclear
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winter. Or we can look at forest fires
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that actually can pump smoke up into the
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stratosphere.
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or we look at volcanic eruptions. Here's
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one of my favorite paintings by Edward
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Monk. It's the red and yellow is the
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volcanic sunset that he saw over the
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Osaw Harbor in 1883 after the Crocatile
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eruption. And 10 years later, he painted
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this this famous painting. And that's
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how I I feel about this. And so uh so we
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can learn about this from volcanic
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eruptions. The Tambbora eruption took
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place in
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1815 and the next year was called the
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year without a summer. The climate was
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about couple degrees Fahrenheit colder
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around the world because of the effects
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of this volcanic eruption. That summer
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in 1816, Mary Shelley, Percy Shelley and
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and Lord Byron were taking their
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vacation in this house on the shores of
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Lake Geneva. and they wanted to go
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hiking and boating, but it was go cold
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and dark and gloomy and they couldn't go
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outside. So, they said, "Well, we're
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writers. Let's try and have a contest to
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see who can write the scariest ghost
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story." And Mary Shel wrote Frankenstein
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inspired by the climatic effects of a
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volcanic eruption. Now, Byron didn't
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write a book, but he wrote a poem called
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Darkness, which I learned about from
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Russian scientists in the 1980s who had
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read it in a Russian translation, and
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sounds just like nuclear winter. I had a
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dream which was not all a dream. The
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bright sun was extinguished, and the
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stars had wandered darkling in the
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eternal space, rayless and pathless, and
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the icy earth swung blind and blackening
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in the moonless air. And mourn came and
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went and came and brought no day. And
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men forgot their passions and the dread
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of this their desolation. And all hearts
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were chilled into a selfish prayer for
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light. And they did live by watchfires
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in the thrones, the palaces of crowned
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kings, the huts, the habitants of all
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things which dwell burnt for beacons.
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Cities were
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consumed. So what does this mean? Uh
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Brian Ton and I last year wrote an
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article called self assured destruction.
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We used to think it was mutually assured
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destruction that if one country attacked
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the other, the other would attack you
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back and everybody would die and that
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would deter you from attacking. But now
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it turns out the use of nuclear weapons
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would be suicidal. If you attacked
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another country and they did nothing,
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the smoke from those fires would come
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back and get you. So you can't use them.
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You can't use nuclear weapons. Why do we
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keep so many? Now, President Obama and
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President Midv signed a the new start
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agreement in Prague in 2010, and this
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pledged each country to go down to about
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2,000 nuclear weapons by 2017. But our
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calculations showed that would still be
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enough to produce nuclear winter. And
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so, we really need to get rid of them
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much faster than that than that. Only
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nuclear disarmament will prevent will
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prevent this possibility of this
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catastrophe.
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And Obama, you might remember last week,
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offered to bring the US arsenal down by
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about a third. And that's great. That's
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sets an example for the rest of the
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world. But how can we expect Iran not to
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have nuclear weapons if we we keep ours?
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It's like sitting on a bar still telling
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people not to drink. Why?
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Now the the the uh problem with our
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weapons is not no rational person would
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use them but there have been cases of
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panic cases of irrational people and the
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closest we came to a nuclear war was in
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the uh 50 years ago during the Cuban
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missile crisis. This is one of the
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Russian missiles that was given to Cuba
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with atomic weapons on and we're really
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lucky that we ended up without a nuclear
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war then. I took that picture a couple
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months ago in Havana. And as John said,
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uh uh one person uh found out about my
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work and invited me down to Havana and I
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gave a talk in uh with Fidel Castro
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sitting at the front for an hour. And
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this is a signed picture uh go to my
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website, you can see more of those. And
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uh uh nine days later, he wrote an
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essay. He said, "While the United States
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and Russia each committed to reducing
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their operative nuclear arsenals down to
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some 2,000 weapons in Prague, the only
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way to prevent a global climate
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catastrophe from taking place would be
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by eliminating nuclear weapons." So,
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that's a good sign. He got it. Now, I
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just need the people that have the
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nuclear weapons still to get it, too.
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Uh, and there's a good sign. There was a
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a meeting in Oslo in Norway in March
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where it's called the humanitarian
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impact of nuclear weapons and 132
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nations attended and they agreed about
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this. You know the there are other
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weapons of mass destruction that are
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prohibited by international treaty. You
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can't use chemical weapons. You can't
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use cluster munitions. You can't use
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biological weapons. But nuclear weapons,
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the worst weapon of mass destruction is
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not prohibited. There is no treaty
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abolishing them. That's what we have to
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work toward. and all these countries
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agreed to it and then there's going to
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be another meeting in in Mexico to try
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and put pressure on the countries with
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them. So, we're going in the right
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direction. Now, you might say, "But, you
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know, they're useful. Uh nuclear weapons
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the course of World War II." That's not
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true. We'd already burned 66 cities in
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Japan. Two more didn't make a
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difference, and the Japanese gave up
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because the Russians came to the war.
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You might say killing all these people
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will will win a war. It won't. killing
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killing soldiers will you might say
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there's nuclear deterrence well which
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nuclear look look at what happened in
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the past the Russians invaded Eastern
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Europe when the US was the only nuclear
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power that didn't deter them the
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Argentinians attacked England in the
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Faulland Islands England was the one
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with nuclear weapons who won the first
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Afghanistan war who won the second one
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the country with nuclear weapons who won
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the war in Vietnam so nuclear weapons
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don't deter anybody from attacking you
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and uh you can't prove that they've kept
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the peace even though we've been lucky
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enough not to have a nuclear war and you
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you can't get rid of them of the
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knowledge of them but you can get rid of
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them. So how have I made you
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feel? So I'm really sorry you know it's
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bit been a bummer I've told you about
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this horrible thing. Uh but the question
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is what do you do about this
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information? As Mark Twain said denial
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ain't just a river in Egypt. The natural
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thing is to try and forget about it and
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go home and forget about it. But
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actually, what you can do is put it to
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work. You have to work. Join the
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international movement to try and get
00:17:18
rid of nuclear weapons. And there's a
00:17:20
couple organizations. One's called
00:17:21
Global Zero, global zero.org. The other
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is I can the international campaign to
00:17:26
abolish nuclear weapons,
00:17:27
iicanw.org. And it's it's it's starting
00:17:31
up in the United States. And you can go
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to these places and join it and try and
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rid the world of nuclear weapons. So, we
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have the luxury of worrying about all
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the other problems you've heard about
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today. Thanks very much.
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[Applause]
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[Music]
