Pushkin. You're listening to Brave New Planet, a podcast about amazing new technologies that could dramatically improve our world or if we don't make wise choices, could leave us a lot worse off utopia or dystopia. It's up to us. In the symbolist mountains on the island of Luzon in the Philippines, there lies a volcano named Mount Pinatubo. For five centuries, it had lain dormant.

But on Saturday, June 15th, 1991, it erupted, causing one of the most cataclysmic events of the 20th century.

Torrential rain has mixed with volcanic ash to form a gray mud covering vast areas of the northern Philippines. The ash folds up to 700 kilometres from Mount Pinatubo.

Nearly 20 million tons of sulfur dioxide were hurled into the stratosphere. The effects of the eruption were felt around the world.

In the following 15 months, average global temperature dropped by roughly one degree Fahrenheit.

Why? Because the sulfur dioxide released by the volcano reflected back a fraction of the sun's energy, preventing it from reaching the earth. The notion that huge volcanoes might affect the weather is actually an old one. Ben Franklin proposed that the severe winter of 1783 to 84 was triggered by a massive eruption in Iceland the previous summer. In 1965, inspired by the volcano theory, science advisers to President Lyndon Johnson proposed developing technology to pump sulfur dioxide into the stratosphere to offset global warming.

But the idea didn't go far because they had no good way to test them, in 1991, Mount Pinatubo ran a test for us.

It seemed to confirm the hypothesis.

The proposal started to gain attention.

Point is this if the problem gets bad enough to do something about, well, don't you want to have something to do? The idea of that is to essentially mimic nature, which is what happens when a volcano blows, a big volcano blows.

That's Stephen Dubner, who touted the idea in his 2008 book Super Freakonomics as a quick fix for global warming.

In politics, the idea attracted strange bedfellows, including former Republican Speaker of the House Newt Gingrich, Texas Republican and climate science skeptic Lamar Smith, and 20-20 Democratic presidential candidate Andrew Yang.

It even made it into the Netflix comedy show The Fix, where comedian D.L. Hughley recommended blowing up a volcano to save the world.

So let's find some volcano in the middle of the ocean, far away from civilization, and blow it to f up the idea.

Well, not blowing up volcanoes, but spreading sulfur particles to decrease solar radiation is a kind of climate intervention that some people call solar geoengineering. It's gotten enough traction that the U.S. National Research Council organized a scientific committee to study it.

And it's not just theoretical. Some Harvard scientists are planning to launch an experimental balloon to start learning how to hack the planet.

Today's big question with the climate crisis becoming more and more desperate, should we get ready to alter the atmosphere of planet Earth, solar geoengineering? Can it protect us from climate change? Do we need it? And what could possibly go wrong? My name is Eric Lander, I'm a scientist who works on ways to improve human health. I helped lead the Human Genome Project and today I lead the Broad Institute of MIT and Harvard. In the 21st century, powerful technologies have been appearing at a breathtaking pace related to the Internet, artificial intelligence, genetic engineering and more.

They have amazing potential upsides, but we can't ignore the risks that come with them. The decisions aren't just up to scientists, politicians, whether we like it or not. We all of us are the stewards of a brave new planet. This generation's choices will shape the future as never before.

Coming up on this episode of Brave New Planet Blocking the Sun. We'll talk to one of the leading proponents of the technology. So solar tuition can with total confidence, and this is not an overstatement, restor temperatures to pre-industrial.

We'll hear from two experts who weighed the benefits and risks for the National Academy of Sciences. I can imagine this launching climate wars.

Some third party might actually get to the point where the climate in their part of the world had become intolerable and they would unilaterally decide to modify the planet's climate without consulting with anyone. And we'll speak with the executive director of Sunrise, a movement of young people working to stop climate change about whether it's time to consider what to do if all else fails.

I understand the desperation. I understand the urgency. I understand that we need to kick everything into high gear.

So stay with us. Hey there, I'm Bill Nye, host of Science Rules, where we talk about all the ways in which science rules our universe, you never know what you might learn on our show.

Evolution does some pretty funky things. We talk about birds learning from other birds. This is what we call a delicious dilemma in astrophysics. Oh, hey, here's a thing this field doesn't actually understand. Stay tuned. Turn it up. Wow. There are worlds outside our solar system. There are thousands and thousands of other worlds. I can totally talk to this cuttlefish.

We're also bringing you expert analysis on the biggest science story of them all, the coronavirus.

This is about the health of the whole planet. Everybody has to take a calculated risk. I've just reviewed this literature. How bad does it have to get before everybody pays attention?

Whatever your problem, wherever you are in the universe, science rules, science rules is out right now. Subscribe and Stitcher, Apple podcast, Spotify or wherever you listen.

Chapter one, Climate Crisis. To get up to speed about the climate crisis, I went down to Washington, D.C. to visit one of the nation's leading scientists, someone I know well.

So my name is Marcia McNutt. I am a Marine geophysicist as a geophysicist.

What's the coolest thing you've been involved in?

There are so many cool things that geophysicists get to do. I've been down to the bottom of the ocean to see volcanoes erupting on the seafloor. I got to stand on the South Pole on the 100th anniversary of Amazon's first conquest. I have been to Outer Mongolia with nomadic tribesmen studying the birth of mountain belts. Geophysicists get to go a lot of very unusual places and do very wonderful things.

Marcia McNutt has been a Professor Dimity, head of the Monterey Bay Aquarium Research Institute, director of the U.S. Geological Survey, and the editor in chief of Science, the nation's leading scientific journal. Today, she's president of the U.S. National Academy of Sciences, an institution created by Abraham Lincoln in 1863 to advise the U.S. government.

It prepares major reports on crucial scientific questions facing the country.

I wanted to talk to Marcia McNutt because just before becoming president of the Academy in 2016, she chaired the academy's report on climate intervention. And I also talked to another of the authors of that report.

My name is Rapier Humbard. I'm the HALLY professor of physics at the University of Oxford.

I hadn't met Ray before. He's a dead ringer for Santa Claus. He's also an expert in planets, not just our own planet, but also exoplanets, the thousands of planets outside our own solar system.

My favorite planet is 55 concrete e, which is so hot it has a permanent lava ocean on the dayside.

And where is that located? It's around the star 55 concrete, which is not quite a visible star, but it's near the claw, one of the claws of the Scorpion Scorpio.

And that's your favorite planet? Well, they say it's the one we're having the most fun with right now. I see. It's not the vacation on not it's not a it's not one of the vacation sites unless you like lava beaches and so forth.

So I talked with Marcia and Ray about the current state of climate science.

Now, I shouldn't have to say this, but just in case you've been living on an exoplanet or in a state of deep denial, there's no serious question that climate change is real or that it's largely due to excess carbon dioxide from burning fossil fuels, causing a greenhouse effect.

Here's the science in a nutshell. A greenhouse lets you grow greens in Green Bay, Wisconsin, in the middle of the winter because the glass lets light pass through but holds the heat in.

The thicker the glass, the better the heat retention.

CO2 does the same thing for the Earth.

It lets sunlight pass, but retains much of the resulting heat. CO2 has been increasing sharply over the past century to levels unprecedented in human history.

And as a result, the earth is getting hotter. The last six years rank is the sixth hottest years in recorded history. There is a lot more attention to global warming amongst the public, in the press and amongst politicians now that we are starting to see some of the effects, what we've seen with just about a degree of warming is nothing compared to what you get with the second degree of warming swath of Puerto Rico. Under water, roads turn to raging rivers.

Millions of people affected by devastating floods across South Asia, historic fires devastating to Australia.

More than 100 wildfires burning in the Arctic. Firefighters in California continuing to battle some dangerous, fast moving wildfire.

Five of the six largest infernos in state history because of the release of CO2 into the atmosphere from the burning of fossil fuels. Primarily, we are entering basically an unknown regime of rapidly changing climate. It is very difficult for anyone looking at the data to say with any confidence that in this future that we are entering will continue to be conducive for human habitation. Once you enter that zone, you basically can't back up. The dye is already cast and every projection shows that we have it most decades to act.

What are the sort of events we expect to happen as as we have more and more CO2 in the atmosphere? What do we see happening now and what do we imagine happening in the future?

So what we see happening now are things like ice sheets melting, sea level rising, more energy in the atmospheric system, which leads to more storminess, higher amounts of rainfall, stronger hurricanes, areas of the country that used to be pleasant to live in now becoming uninhabitable because of storm surge and high tides. We're seeing death of coral reefs because the oceans too warm for them.

Some of the things that are more complicated, but likely to be far more damaging are the longer droughts, the interactions between ecosystems, things like the bloom and plankton coming earlier in the spring when the animals that need to feed on them haven't yet returned from their migration. So you basically get animals dying of starvation.

Chapter two, the wet bulb temperature. When scientists describe global warming, they usually talk about average temperature rise, for example, take the 2016 Paris Climate Agreement, that's the U.N. agreement supported by 194 countries, but sadly no longer including the United States.

It aims to keep the average global temperature rise below two degrees Celsius.

The problem is that an average temperature rise of two degrees Celsius sounds puny, even if you convert it to roughly four degrees Fahrenheit.

After all, temperatures can fluctuate by 20 degrees Fahrenheit over the course of a day. What's the big deal?

I worry that we as scientists have perhaps done a disservice to climate change by talking about average changes because the average doesn't sound so bad.

But when you talk about how the extremes are likely to change, that is when it gets very scary. One of the aspects of climate change that scares me the most is if instead you measure climate change, by how many days in a certain location is the temperature likely to exceed the wet bulb temperature?

What's the wet bulb temperature? It's basically the difference between life and death, your body is always generating heat, and to keep your body at a constant temperature, you need to radiate away the excess heat. If you can't, you'll die on a cool day. It's no problem. Your skin can lose heat directly to the air, but on a hot summer day, you need to sweat so the evaporation carries away the heat. Now, if the temperature, the humidity get too high, a person literally can't sweat enough to cool themselves.

What's the limit? Well, at 50 percent humidity, you can't make it much past 112 degrees in the shade.

So unless that person can get to some place that's air conditioned, they will literally overheat and suffer heat stroke. There are many places on this planet right now in India, Southeast Asia, Africa, where the number of days that are exceeding the wet bulb temperature are going up dramatically every summer.

We're even seeing life threatening temperatures across temperate zones in Europe with record highs recorded in Germany, Netherlands, Britain and France, with the latter hitting roughly 115 degrees Fahrenheit.

So a better way to think about the effect of climate change might be the number of days that a region becomes uninhabitable outdoors if you go from, say, one degree of warming to two degrees of warming.

A lot of the damages scale linearly. If you used to have, say, something like 30 days of life threatening heat waves in some place, we go to something like 60 days.

When you go to five to two degrees, what would happen if we blow past two degrees Celsius? It's more like a global rise of four degrees Celsius.

If you get to four or five degrees global mean warming, then you get to the situation where perhaps half of the earth becomes uninhabitable outdoors for mammals. Then air conditioning becomes not a matter of comfort, but a matter of life support.

It's like living in a space station and a power failure becomes not just a matter of inconvenience, but Megadeath.

Of course, most people on Earth don't have access to homes with air conditioning. It's these people who will suffer.

And then you also have to think about all the animals that are not going to be living in air conditioning. What happens to elephants?

What happens to cattle is a very different world. Unfortunately, we're not making much progress on reducing CO2 emissions by almost all scientific accounts.

If we don't drastically change our fossil fuel consumption, we're going to blow past the target of two degrees and the Paris agreement.

The problem is it's really hard and really slow to change the world's energy systems.

To move to renewables requires electrifying your energy system that that's really the only realistic way to do it. Electrifying the system requires building transmission lines. My homes in California, it can take three years just to permit a new transmission line.

Replacing power plants takes even longer since they're designed to last for decades.

Power grids generally evolve over a 40 year timescale. So this is why many scientists and many policymakers are concerned about taking an infrastructure system that has a 40 year renewal rate and trying to respond to a problem that needs immediate action.

Here's where the volcano strategy comes in. We've already tampered with our atmosphere and we're starting to feel the consequences. Why not temper some more to prevent some of the warming saving lives and curbing suffering? That's the idea behind this type of climate intervention. Is it time to start experimenting with the technology? Chapter three, tiny space mirrors. I arranged to speak with Professor David Keith. He's one of the leading proponents of solar geo engineering research and he's aiming to run a small scale test.

David agreed to bicycle down from Harvard to the other end of Cambridge, where I work at the Broad Institute.

So solar tuition can with total confidence and this is not an overstatement. Restor temperatures to pre-industrial.

Long before David started thinking about solar geo engineering, his scientific career had an unusual start. His first job was as a research assistant in the Arctic the year I was there.

We were really working on walruses and we were trying to learn how to identify them by their calls and then we had to breed them with cattle brands that we bought in Alberta. And my job as a young guy was to carry the brands that was the right part. And the propane tank and the kind of flamethrower, anything that you needed to heat up the Brads. I'd done way more big outside time than most people. So probably more than a thousand kilometres of kind of an Arctic ski trips, expeditions, whatever.

Would you call yourself an environmentalist in this topic? This is such a big fight. You know, I feel like it's for other people to judge, but I'd say I've been to Earth first rallies and I've done our actions. And I yeah, I think the short answer would be yeah.

He began studying global warming when he arrived at MIT in the 1980s.

I stumbled into this really cool group of students in between Harvard and MIT grad students who were working on climate change, both the science and public policy and interdisciplinary way.

Today, David focuses on solar geoengineering engineering.

He's mostly focused on stratospheric geo engineering, which is what we've been talking about, mimicking the behavior of a volcano by spraying reflective particles into the stratosphere.

But there's actually several different ways of changing the Earth's solar radiation.

There's the idea of brightening a certain kind of marine boundary layer cloud.

Brighter clouds would reflect more sunlight.

There's the idea of thinning kind of cirrus cloud by adding silver iodide or something like that, wispy or clouds would trap less of the sun's heat.

Then there's space based technologies that you could build big orbiting mirrors or what have you to make a difference.

Space mirrors would need to be huge. With a surface area about the size of Greenland, it wouldn't be cheap to get them into orbit.

I think if you think in the next decades, I think the idea of space space stuff is ridiculous. But if you think about this is something humans do over a century, a century and a half, I don't think it's crazy to think that we might do space based things.

For now, though, the best approach would be stratospheric intervention, putting reflective particles into the atmosphere. You can think of them as tiny space mirrors just at a lower altitude. Planes would fly around the stratosphere, spraying plumes of sulphur dioxide or similar chemicals. It would be surprisingly cost effective.

The cost to kind of begin a program that's putting material quantity of stuff in the stratosphere is probably just a few billion dollars. The kind of climate damages we're talking about, a global basis are of order trillion a year. So the idea that a few countries spend a few billion a year, that's a small off number. But I don't think that cost is going to be the direct driver.

A few billion dollars to clean up a trillion dollar mess. Sounds like a pretty good deal, at least on paper. What could possibly go wrong? Chapter four, what could possibly go wrong? When the National Research Council scientists sat down to write a report on solar geoengineering, the first thing they realized was that calling the technology solar geoengineering might be seriously misleading.

I never liked the term geoengineering myself because engineering is a term we generally apply to precise management or design to control systems that we actually understand. But what is generally called geoengineering is something that is really hard to try out, hard to resolve.

The main questions about this is basically throwing up these particles into the stratosphere at the whim of the jet stream. They go where they will.

It's not like a house with thermostats in every room where you can turn this room a little cooler and maybe this one not so cool and turn this one off because no one really needs it in this room. So we prefer the term albedo modification, even though it sounds kind of wonky.

Albedo is the scientific term for the reflectivity of a planet.

Unfortunately, albedo modification wouldn't mean anything to the general public. The other extreme, some people use the term hacking the planet, there's a lot of sort of techno optimism involved in the people that are doing research on this, which is very similar to the sense of pride where you're hacking a system. And it is a sort of cool thing to contemplate. And if we didn't have to live on the planet, I'd be really interested in it myself. But it is dealing with the only home that we have and and has potentially really very serious consequences.

Ultimately, the science is settled on the neutral term climate intervention.

I like the term climate intervention because just like with interventions in, say, a person who has a drug problem or whatever, you're not guaranteed to achieve the outcome that you want. You're having an intervention because you know something is wrong, but you just can't be sure that you're not going to actually make the situation worse.

But you may be so desperate that you really need to do something.

As the scientists dug into the problem, they recognize that the perfect climate intervention would simply be to dim the sun by one or two percent. Unfortunately, though, the sun doesn't have a dimmer switch and using particles to block the sun's rays isn't quite the same thing. You can control the average global temperature, but the impact across the globe may be very uneven.

If you put aerosols up in the stratosphere, tiny little particles in the stratosphere, they don't just sit there where you put them. They get blown around by the stratospheric winds. They take up water, they get bigger. Bigger particles have different reflective properties and smaller particles. They tend to get bunched up near the poles eventually and fall out near the poles.

You don't necessarily get an equal distribution between the Northern Hemisphere and the southern hemisphere that might have serious consequences for the Earth's climate.

Modeling has shown that if the aerosols were to preferentially bunch up in one hemisphere, that actually shifts the tropical rainfall patterns into the opposite hemisphere. So you would actually create potentially serious droughts. That's one example of the sort of thing that could go wrong.

And inadvertently sort of put it in the simplest terms, you're saying we could put up aerosols and end up completely surprised by the winners and losers in the climate effects of that.

Right. So it's hard to guess in advance how particles will distribute in the stratosphere. They might cool certain areas of the globe, but leave others vulnerable to droughts and heat waves. Moreover, it's hard to run a local field test.

We can't just say, OK, we're going to albedo modify over El Paso, Texas. And does El Paso get cooler? And what happens to El Paso's rainfall? And are there any negative effects of sulphur particles falling out of the air or anything?

You can't do that because once I put it up over El Paso, how long before it distributes around the world?

So most of these injections have to be done near the equator because that's the best place for distribution. And they very quickly get into these stratospheric currents that distribute them. And within two years, it's all dissipated. It's all gone. It all filters out. So you would have to reinject every year to two years. So one thing you can't say at least, is if you're willing to tolerate a global experiment, at least it would go away. Let's let's pull that thread for a second.

Suppose somebody were to do a global experiment for a couple of years.

Now, here's the issue with doing an experiment, a global experiment on albedo modification. We have no idea how to attribute whatever might happen during those two years to the experiment itself versus natural variability in storminess, droughts, floods, whatever. And you can be sure anyone who might have been impacted during that period by a hurricane, a drought, a flood would say, bingo, you did this experiment and I got flooded out of my house or I had a hurricane take out my barn or I had a drought that wiped out my herd of cattle.

You owe me there'd be lawsuits all over the place.

There would be lawsuits all over the place. And who's going to indemnify the person who does the experiment against. The lawsuits, do you think there's any insurance company that wants to take on that policy? Chapter five, The Big Balloon. Despite the challenges, David Keith wants to try and experiment a very small experiment. He's working with a team at Harvard on a project called SCOP X, so Skopec is about trying to improve our models of the way stratospheric aerosols and chemistry work in little ways that are relevant for improving understanding of the risks and efficacy of solar geoengineering.

Keith and his colleagues want to send the balloon carrying particles high into the atmosphere, puffed them out and see how they disperse and reflect sunlight. How big is this balloon?

Just give me a picture of balloons are like 20 meters diameter of 60 foot wide balloons going up. And what's attached to the balloon?

We're building the balloon gondolas. Still what you call it. The gondola has two little propellers that are more to kind of move it around slowly. And it has our data system. It has the batteries to run it. It has it has the thing that generates the particles. It has a particle sensor to measure the particle size distribution. And the whole thing is on a winch so it can winch itself up and down relative to the balloon.

So the balloon will spray particles and then right around measuring how they disperse the amount of material the team is going to release is actually tiny a kilogram or something, which for the sake of argument, that turns out to be the amount of sulphur that a commercial aircraft would normally fly and releases at about a minute's light.

While its physical cargo is tiny, the balloon also carries with it a lot of questions about regulation, scientific knowledge, symbolic value and possible political misuse. While there's no serious scientific case that spraying a kilogram of particles can cause any physical harm, some people still think it's very dangerous.

There's a group of people and by high quality polling, we know this group of people is like a third of Americans who believe that the government is already spraying toxic chemicals from airplanes for mass murder or climate regulation or something.

And so those people have conflated that with some of the scientific work on some geoengineering. So when they Google around or there's lots of sites that will have me as a mass murderer, indeed, I once got a voicemail. My favorite one that my kids enjoyed a lot was a voicemail that said that I was 10 million times more evil than Hitler and Stalin. And then it's not quite clear if the gentleman is saying that that it's combined or separately.

But it's not just conspiracy theorists. Even some of David Keith's friends, like Repya Humbard, are opposed to snowpacks.

It is actually one of the joys of science that at least among scientists, you can have very vehement professional disagreements and still remain on good terms.

What's really funny is, at least from my perspective, I have huge respect for both scientifically actually as a human.

There's an article, the most recent article he wrote, which is actually the most personal and attacking me. It was like attacking the Harvard program. I forget exactly what it said, but it was like pretty direct, you know, both smoking barrels aimed my way.

That was published just a few weeks after I had a wonderful dinner with him and his wife. Actually, I visited him in Cambridge or Oxford.

And we we talked about exoplanets.

We talked about American politics. And we mostly actually avoided talking about this topic. We now disagree.

I don't imagine that David would pay any attention to what advice I gave him, but I would advise him to just drop scope.

X ray has multiple objections. On the one hand, the experiment is too small.

Releasing a few particles won't teach us anything important about the large scale planetary processes that would matter most.

I still lean towards calling them Stuntz and that, well, they have some scientific payback. They don't really address the biggest questions we have.

You can't do that with just a puff experiment. If you really want to resolve some of the questions that are going to be a make or break thing for what would happen if you the albedo modification, there are 100 other things that are more important scientifically.

On the other hand, raise concern that the experiment will open the door to ever larger solar geoengineering efforts before there are any rules in place.

It's the risk that by doing a small experiment that crosses a red line, you're opening the door to escalation. If you can do a small experiment, well, next year someone's going to do a bigger experiment. It represents the thin edge of the wedge.

What what can of worms or are you opening?

But Ray's biggest concern is more fundamental.

Solar geoengineering is wildly, howlingly barking mad and no research developments have changed my opinion one iota.

Chapter six, The Sword of Damocles. What makes Rapier Humbard call solar geoengineering wildly, howlingly barking mad?

It boils down to two things. First, it doesn't solve the real problem. As long as we continue to emit CO2, it continues to accumulate in the atmosphere. Much of it remains for tens of thousands of years, and the greenhouse effect keeps increasing. Climate intervention just masks the problem by reflecting away sunlight while we keep pumping vast amounts of CO2 into the air. The second problem is solar geoengineering could create a sort of time bomb.

My biggest worry. In fact, the worry that underpins all my other worries about the possibility of deploying albedo modification stems from the mismatch in timescales, the mismatch and timescales.

Is this well, much of the CO2 sticks around for tens of thousands of years. The sulphur particles that would be used for geoengineering, they disappear very quickly. They need to be replaced every couple of years.

You're committing the entire future of humanity to doing this essentially forever. When have we ever saddled the next 100000 years of civilization with an obligation to do something without fail each and every year forever?

Essentially, there's no precedent in human history. If you then stop, if you stop because there's a global war, there's a global depression or disputes over what the effect of this is, or you find some horrible side effect that you just can't bear. If you stop doing this albedo modification, then within about 10 years you have nearly the full effect of all the pent up warming from that carbon dioxide in the atmosphere. That's what we call termination shock. Everybody on the planet living under the sword of Damocles, knowing it could fall at any minute.

Exactly how much pent up warming would depends on how much CO2 we've allowed to accumulate a rapid warming of two degrees Celsius would be bad enough rise of four degrees C within a decade, making large swaths of the planet uninhabitable outdoors.

Most of the year that would be catastrophic. I asked Ray if he thought solar geoengineering would ever make sense.

The only scenario is if you actually had already committed to getting to zero carbon dioxide emissions in a reasonably short window of time or if you had developed technology for removing carbon dioxide from the atmosphere.

In other words, if we had largely solved the problem and only had to buy a little bit of time, unfortunately, we're not on target to get to zero net emissions. And we're very far from having affordable technologies for carbon capture from the atmosphere.

Chapter seven, Climate Wars.

If the climate crisis continues to deepen, who would decide whether and when to deploy solar geoengineering, would the United Nations try to forge a global consensus or because it's not so expensive, might some nations just try to do it on their own?

I can imagine some country could just start deploying albedo modification just because of their own perceived self-interest.

Imagine a humid nation that is seeing its elderly people dying from heat stroke.

They may think putting a bunch of particles up in the air is a pretty simple solution to it. And if that means that the Canadian wheat harvest fails, well, that's their problem.

I can imagine that conflicts that could arise when nations start tinkering with the composition of the stratosphere.

I can also imagine this launching climate wars because there are quite easy countermeasures. The kinds of aircraft that would be actually spewing out sulfur dioxide into the stratosphere there, they're slow moving. They're easy to target by fairly simple missiles there.

Other kinds of countermeasures you could think of, for instance, if other countries used geoengineering to slow climate change. But Russia preferred to let the earth keep warming because it would open the Arctic Ocean year-round Russia could interfere or they'd have to do would be to increase their coal burning, increase the CO2 to offset the albedo modification.

Russia could actually even do more harmful things, releasing methane into the atmosphere. They could start manufacturing sulfur hexafluoride, which is an incredibly potent long-life greenhouse gas.

It turns out that the fear that countries might start acting on their own was the initial inspiration for the National Research Council report.

The intelligence community was concerned that some third party might actually get to the point where the climate in their part of the world had become intolerable and they would unilaterally decide to modify the planet's climate without consulting with anyone.

Some argue that solar geoengineering is basically ungovernable.

If one country wants the world slightly warmer and another needs that cooler, how could we get a global consensus about who sets the thermostat?

Right now, there is no treaty. There is no international agreement. There is no governance structure that actually prevents anyone from intervening in the atmosphere or the stratosphere to perform some kind of albedo modification.

The Academy has a study underway right now that is focusing on the governance issue and hopefully they will come up with some good ideas of how to take this forward. Chapter eight Sunrise. Given all the problems with solar geoengineering, why are scientists even considering it? The reason is they're beginning to feel pretty desperate while the Paris climate treaty aims to keep global warming to two degrees C on, our current trajectory will blow past that target and may barreled toward catastrophic increases.

Some feel we better be ready with a break glass in case of emergency solution. But is solving climate change really hopeless? A lot of young people have been rising up lately to demand action. They think the answer will require not just science, but political pressure.

17 year old Swedish activist Gratitude Emberg recently gained international attention for her call for a global climate strike and her demands for policy change at the United Nations.

People are suffering. People are dying. Entire ecosystems are collapsing. We are in the beginning of a mass extinction and all you can talk about is money and fairy tales of economic growth. How dare you?

In the U.S., a youth led environmental movement has been organizing to pressure politicians through sit ins, songs and communal action by.

You know, I decided to talk to one of the leaders in what's become a global movement.

My name is Varshney Prakash. I am one of the co-founders of and currently serving as the executive director for Sunrise Movement, which is organizing tens of thousands of people, predominantly young people across this nation to make climate action a priority in our nation for the first time.

So tell me how you got to that point. Like, what was your path?

I am the child of two South Indian immigrants. India is a place that is being ravaged by the climate crisis, whether it's through, you know, drought and water wars or farmers committing suicide by the tens of thousands or a climate fueled floods worsening and impacting people. And I remember it was like the fall of 2015 when a series of really horrific floods hit my family's farm in southern India. And I remember roads and sidewalks that I had walked on that my dad and I had grown up on, just covered in feet of water and seeing dead bodies and people walking chest deep in water for miles to sanctuary.

And it was this major moment of reckoning of realizing that the climate crisis was here. There were people dying as a result of it. It wasn't an issue 30, 40, 50 years in the future. And the movements that we had in that moment were not growing or weren't as powerful as we needed them to be.

To address this crisis, Farchione joined a group of young climate activists who wanted to drive big change.

We embarked on this process for almost a year of strategic planning, of research, of study, of an assessment of the field studying things like the civil rights movement, queer movements, women's suffrage, Vietnam War era movements, and then contemporary movements as well, like the Movement for Black Lives, Occupy Wall Street, others to see how do people make these grand societal transformations that we need to make to stop climate change? And how do we emulate that?

Out of this work came Sunrise Movement, which aims to bring together millions of people, especially young people. As you may have heard, they've proposed a program called the Green New Deal. One important element of the program is funding innovation to drive down the cost of renewables to the point where they're cheaper than fossil fuels.

But the aims of the Green New Deal are far more ambitious.

It can be thought of as a a decade long economic mobilization, really to stop climate change at a scale not seen since World War Two, everything from stopping climate change to creating tens of millions of good high paying jobs, virtually eliminating poverty in the process, everything from addressing agriculture systems to industry to power generation and land use, forestry, everything under the sun that we would need to deploy to address the crisis. It won't be just one piece of legislation.

And it was the same way with the New Deal. It wasn't there wasn't a New Deal, Bill. There were hundreds of bills and projects that FDR and others implemented. They were really embracing this ethos of experimentation, of doing whatever it takes to to get Americans out of the Great Depression and put money back in the pockets of working people.

The Green New Deal resolution is more of a framework than a specific piece of legislation at this point. Still, the idea has prompted a range of concerns. Climate change deniers belittle it.

They want to take your pick up truck. They want to rebuild your home. They want to take away your hamburgers. This is what Stalin dreamt about but never achieved.

Many scientists and economists view achieving carbon neutrality within ten years is a pipe dream, given the slow rate at which power plants are replaced. Others think it's trying to do too much to solve climate change, poverty and racial injustice all at the same time, but maybe the Sunrise's are onto something very important in the way they're building the coalition, packaging them as one thing.

This sounds sort of counterintuitive to some people, but it actually makes it more popular. The parts of the Green New Deal that are the most popular are the parts around job creation, are the investments in sustainable agriculture and renewable energy technology.

Foschini contrasted the Sunrise movement's approach to previous climate change legislation, efforts like the Waxman Markey bill in 2009, the last 40 years of focusing on just like a singular tax or a singular cap and trade model or something that people cannot understand as making basic improvements to their lives. That's why a lot of the reason why Waxman Markey failed in the Senate 10 years ago because there wasn't the public will and the public support.

She talked to Senator Markey, who sponsored both the 2009 bill and now the Green New Deal resolution.

I asked him, what is the major difference that you are seeing in 2019 versus, you know, 2009? And he said the number one difference and what we need so badly is that we actually have an army of people out there pushing for these solutions.

I asked Marcia McNutt what she thought about Sunrise movement.

I love it. I think it's critical. I mean, if it's not going to be that generation, then who they're the ones that are going to still be alive in 2050. It's not going to be me and it's going to be their children that are going to be alive in 2100 that are going to be inheriting this parched earth. It's incredibly important that they stand up and say, no, this is not their trajectory that I want for the planet.

And when politicians vote with a two year time horizon in their mind or if they vote special interest groups who are looking only at their corporation, one year ROIC, that is absolutely criminal.

So what would you say to the people in the sunrise movement? What what encouragement or message would you say to them? I would say they are just like the people who stood up to the Vietnam War and every other injustice. You know, this is an injustice to all of humanity. So after talking with Varshney about Sunrise movement, I asked her whether she and her fellow activists thought solar geoengineering might be an important tool in addressing climate change.

She was unconvinced regarding the technology as a distraction from solving the real problem, if the issue is decarbonizing and the long term problem is taking carbon out of the atmosphere, things like geoengineering don't even do that. But and so don't get me wrong. I understand the desperation. I understand the urgency. I understand that we need to kick everything into high gear. But I think, like, we are putting carbon into the atmosphere. Perhaps the easiest fix that we have is to stop putting carbon into the atmosphere.

Chapter nine. The moral hazard. I understand why climate change activists want to stay laser focused on decarbonising the world's energy supply, but at the same time, is there any harm in also having climate intervention as a backup?

Unfortunately, the answer is there might well be some people worry that pursuing solar geoengineering in parallel might actually make it harder to get the world to solve climate change.

Humans tend to address problems only when they feel the consequences, such as heat waves, wildfires, floods and hurricanes.

If blocking the sun decreases natural disasters caused by global warming, will we become complacent about solving the real problem?

It's like taking a painkiller instead of actually having the cancer taken out.

Eliminating one of the symptoms of carbon dioxide emission, which is the planet getting warmer, makes it easier to ignore the root cause of the problem and just continue emitting.

This is what economists call the moral hazard problem. The idea that people who have insurance against disasters aren't as careful about avoiding risks.

For example, because the government provides flood insurance for homes on flood plains, homeowners are more willing to keep rebuilding their flooded homes on the same sites. But David Keith is worried about something even more insidious, that the mere prospect of solar geoengineering will be used as a political weapon to deny the need to act on climate change.

At the beginning of this episode, I noted that some of the greatest enthusiasm in Congress for solar geoengineering has come from climate change deniers. That's certainly no accident.

People are terrified that if these ideas get out more in the big world, that they will be seized upon by opponents of climate action, by oil companies, by people who want to block emissions cuts. Those people will claim falsely that solar judiciary means we don't need to cut emissions or that it may mean we don't cut emissions. And they'll use that in the bruising political fight over emissions cuts. That is the underlying, I think, biggest fear. And you sure that, of course, it's a complete vision.

If I'm terrified about it, the certainty that they will try and use it as an argument is there. But that doesn't mean that necessarily humanity will do less emissions cuts. And in the end, those of us who want emissions cuts just have to win on the merits.

Although David Keith is certain his work will be misused by some politicians, he believes it's essential to do the research.

I still think that that fear is not a reason not to know more. You may think or some in your audience to this podcast may think this older generation is a terrible idea and never should be done. Others may think it really could be part of the way we manage climate change. But let me let you all out there in podcast land in on a big secret. We're not deciding now whether or not this happens. We're deciding whether we give the next generation realistic information.

If we keep the taboo going, then we'll hand them basically no information. So sometime in the next decades, some government, maybe the Chinese government, after their monsoon fails, maybe the U.S. government after a massive Category five has New York, maybe the Indonesian government after a big heat wave that kills a quarter million. Some government is going to seriously consider this. And my view is that we'd be better to give them lots of knowledge before they consider it.

But Repya Humbard doesn't buy it.

So David likes to make the case that if we don't do these experiments, we'll just be giving the gift of ignorance to the future. But sometimes the gift of ignorance is a precious gift. And so we have to decide first whether this is a case where the gift of ignorance is precious or a burden. I think if it had been possible to actually give the gift of ignorance about horrible things like nerve gas, if it had been possible to have the gift of ignorance about building hydrogen bombs, whether or not that would have been feasible or not, that would have been a nice cut and ignorance to have.

And again, I'm not saying that necessarily albedo modification is in the same category as these things, but someone has to make that judgment and it has to be made by by civil society in some way.

So where do you draw the line? I, I think that it would be impractical to have any form of governments that forbid computer experimentation.

But when it comes to stuff, kit gear, either a lab experiment, but especially outdoor experimentation, actually stuffing things into the atmosphere, even on a small scale, there is a kind of a clear line there. And so that's where I think there needs to be some kind of discussion. You know, is this a red line worth crossing? Is the scientific payback enough to actually justify crossing this red line? Conclusion, choose your planet. So there you have it, solar geoengineering, it could cool the planet, at least on average, it might buy time and mitigate suffering, but its precise impacts would be uneven and unpredictable.

And it's very hard to test. There could be big winners and losers. It could even trigger climate wars. If we choose climate intervention, we might end up addicted for thousands of years, threatened with rapid, massive temperature increases if we ever stopped. If we don't consider climate intervention, we might find ourselves without options as temperatures keep rising in the decades ahead. Should we start experimenting now so that we'll know enough to be ready, or is it a distraction or even worse, a gift to climate change deniers who use the prospect of solar geoengineering to keep us from solving the real problem?

So the question is, what can you do a lot? It turns out you don't have to be an expert and you don't have to do it alone. If enough people get engaged together, we will make wise choices, invite friends over for dinner and debate about what we should do or organize a conversation for a book club or a faith group or a campus event online, of course, for now in person, when it's safe. And if you hate having to consider these choices about solar geoengineering, then join a group to help stop climate change before it's too late.

You can find lots of resources and ideas at our Web site. Brave New Planet, Dawg. It's time to choose our planet. The future is up to us. And my kids still debate whether I'm their dad is more evil than Hitler and Stalin or Hitler and Stalin combined. That's good to know what the family debates are. That's fascinating.

Brave New Planet is a co-production with the Broad Institute of MIT and Harvard, Pushkin Industries and The Boston Globe with support from the Alfred P. Sloan Foundation. Our show is produced by Rebecca Douglas with Merridew theme song composed by Ned Porter, Mastering and Sound Design by James Gava, fact checking by Joseph Fridmann and a Stitt and Enchante. Special thanks to Christine Heenan and Rachel Roberts at Clarendon Communications.

To Lee McGuire, Kristen Zerilli and Justin Levine, our hand at the road to Mia LaBelle and Heather Fain at Pushkin, and to Eliane Broad, who made the Broad Institute possible. This is Brave New Planet. I'm Eric Lander.