Can We Cool the Planet?

Can We Cool the Planet?

PBS Airdate: October 28, 2020

NARRATOR: Are rising temperatures driving Earth’s ecosystems past a point of no return?

JANE LONG (Senior Fellow, California Council Science & Technology): We can’t go back. There is no path backwards.

STEVE PACALA (Princeton University): Every year the damages are worse.

NARRATOR: We have promising technologies that put the solutions within our grasp, but are we reaching far enough?

FRANK KEUTSCH (Harvard University): We have to have emissions cut to zero.

DAVID KEITH (Harvard University): Even if we stop emitting CO2, we still have the CO2 we’ve already emitted.

NARRATOR: So, scientists are building a new toolkit. It has power to ensure a prosperous future:…

ARMAND NEUKERMANS (Marine Cloud Brightening Project): Our society has to survive.

SHEILA JASANOFF (Harvard University/John F. Kennedy School of Government): We need to reduce the heating effect.

NARRATOR: …cutting-edge solutions…

ALDO STEINFELD (Swiss Federal Institute of Technology Zurich [ETH Zurich]): It’s going to be revolutionary.

LOLA FATOYINBO-AGUEH (NASA Goddard Space Flight Center): It’s like science fiction.

There’s the balloon up there.

NARRATOR: …and high-risk measures,...

FRANK KEUTSCH: I really hope we’ll never have to do this.

STEVE PACALA: It’s really important that humanity has a backstop.

NARRATOR: …in a race to discover, Can We Cool The Planet? Right now, on NOVA.

SHEILA JASANOFF: It’s a new time in the earth’s history, in which we are not just inhabiting our planet, we’re operating as stewards of the very thing that we’re living on.

NARRATOR: Since the industrial revolution, humanity has been running an unintentional experiment in Earth’s atmosphere, pushing the climate to new extremes.

JANE LONG: Things are going to get hot.

Boy, you can feel the heat. This is insane! Oh, my god.

STEVE PACALA: Attitudes have changed rapidly, because everyone can see for themselves the climate change that is occurring.

NARRATOR: A child born today will witness, across her lifetime, a planet transformed by rising temperature.

WOMAN IN FLOOD TALKING TO DOGS: I got you, I got you.

NARRATOR: How did we get here?

JANE LONG: Every time you get in your car, every time you fly a plane, every time you turn the heat on, all of those things are putting carbon dioxide into the atmosphere. And if there’s more carbon dioxide in the atmosphere, there’s a higher temperature.

NARRATOR: And now temperatures have started to spike.

DAVID KEITH: If we keep pumping billions of tons of CO2 into the atmosphere each year, we really will cook ourselves, literally, in the end.

NARRATOR: To stop the worst impacts of planetary heating, we need rapid emissions cuts, starting now.

STEVE PACALA: The developed nations of the world need to go from the energy system they have now to one that emits nothing, zero, in 30 years’ time. The good news is we know how to do that.

Renewables now are the cheapest form of electricity on two-thirds of the Earth’s surface, and it’s going to be everywhere.

NARRATOR: A world of carbon-free energy is coming, but climate impacts are coming faster.

KATE MURPHY (Palo Alto Research Center): Lasers are at power. There it is.

NARRATOR: So, scientists are opening a second front in the battle…

ATTICUS: Sweet. It has power.

NARRATOR: …bringing new technologies to bear on the way we fight climate change…

LOLA FATOYINBO-AGUEH: We now have so much data. This is going to be a gamechanger.

STEVE PACALA: There are a whole class of solutions to actually get this job all the way done.

NARRATOR: …by removing CO2 from the air…

SANDRA SNAEBJORNSDOTTIR (Reykjavik Energy): This little guy, this is just the beginning.

NARRATOR: …converting CO2 from a waste to a resource...

APOORV SINHA (Carbon Upcycling Technologies): We see this kind of as a testing ground.

NARRATOR: …even extreme measures, like shielding us from the sun.

STEVE PACALA: There’s been a technical revolution in the last few years that’s unlike anything we’ve seen in the previous hundred. This is a problem with a solution.

NARRATOR: Can a new wave of climate tech take us the rest of the way to turn down the global thermostat?

FRANK KEUTSCH: We need to look at everything that’s out there: natural solutions, CO2 sequestration, solar geoengineering. There may be this idea out there that nobody has come up with that could be really transformative.

NARRATOR: Cooling the planet means, first, stopping more CO2 from entering the atmosphere and then finding ways to remove it.

But just how much CO2 are we talking about?

SCOTT DENNING (Colorado State University): Imagine you filled the National Mall, all the way from the Lincoln Memorial to the Capitol steps, with coal, and you piled it up, all the way to the top of the Washington Monument, 10 times. That would be a gigaton of coal. A “giga” means “billion.” So, that’s a billion tons.

Now, we actually burn 10 times that much carbon every year. People actually go dig that stuff up out of the ground, 10-billion tons of it, and set it on fire in power plants, in engines, in factories, all over the world.

And then, because that carbon has reacted with oxygen, 10-gigatons of carbon is burned, but it creates 37-gigatons of CO2.

NARRATOR: At our current rate, that’s just one year of CO2 emissions. To blunt the impacts of heating the planet, we need to shrink that number to zero.

But there’s another problem: the gigatons that came before.

JANE LONG: The single most important fact about climate change is that the carbon dioxide that we emit into the atmosphere stays there for thousands of years.

NARRATOR: Year after year, we live with the carbon dioxide we’ve added over time, nearly 1,000-metric-gigatons since the industrial revolution began.

JANE LONG: Almost everything we emit stays there, and it’s staying there until you do something about taking it out.

NARRATOR: Pulling CO2 out of the air…

APOLLO 13 MISSION CONTROL: Clock Start.

Roger.

All Engines.

NARRATOR: …it sounds futuristic, but it’s a problem we’ve encountered before.

JAN WURZBACHER (Climeworks): Remember Apollo 13? That was all about CO2 filtering, right? That was the big problem, how to get the CO2 out of the air.

NARRATOR: In 1970, following an accident, the crew of Apollo 13 aborted a mission to land on the moon.

APOLLO 13 MISSION CONTROL: Houston, we’ve had a problem.

NARRATOR: Forced to return to Earth in a smaller capsule, the astronauts faced a big problem.

JAN WURZBACHER: You’re in confined spaces, people exhale CO2. You need to remove that CO2.

NARRATOR: Every exhale caused carbon dioxide to build up, making the air increasingly toxic.

APOLLO 13 MISSION CONTROL: Okay, now, let’s everybody keep cool. Let’s solve the problem, but let’s not make it any worse by guessing.

NARRATOR: The astronauts survived by modifying their air scrubber to remove more carbon dioxide. Inside the scrubber, negatively charged sites on the filter polarize and bond with the CO2, removing it from the air.

Could something like this work in Earth’s atmosphere?

SCOTT DENNING: There’s not a lot of CO2 in the air, compared to nitrogen and oxygen Imagine a box with 10,000 ping pong balls in it, and four of them are painted black; those are the CO2 molecules. Trying to find those four balls out of that big box full of ping pong balls is hard.

NARRATOR: Removing CO2 from a spacecraft is one thing. Removing it from our atmosphere poses a much bigger challenge. Is it realistic?

JAN WURZBACHER: Most people to whom we told, “We are taking CO2 out of the air,” would say, “You’re crazy.” But here you see a full-scale direct air capture plant. You see it consists of twelve individual modules capturing the CO2 out of the air.

NARRATOR: Jan Wurzbacher is a co-founder of Climeworks, a Swiss start-up, specializing in what’s called “direct air capture.”

JAN WURZBACHER: Through this side, we suck in ambient air with 400 p.p.m., that’s 400 parts per million, CO2. And on the other side, we expel about 100 p.p.m. CO2 content. So, three-quarters are kept inside.

NARRATOR: A filter with highly-reactive chemicals, called “amines,” catches even small concentrations of CO2. Heating the filter then breaks the bond.

JAN WURZBACHER: You release the CO2, and you can extract pure, concentrated CO2. And then you start all over again.

NARRATOR: But generating the energy to do this can produce its own CO2. Their solution for that is garbage.

JAN WURZBACHER: Here, we are on top of the waste incineration plant. The reason why we’re here is the main energy source for our process of CO2 capture from the air: waste heat from the incineration process.

NARRATOR: Heat that would have been wasted instead heats the filters inside the array, which capture nearly 1,500-metric-tons of pure CO2 a year, about what’s expelled from the tailpipes of 300 cars. But capturing it is only half the battle.

STEVE PACALA: Once you’ve pulled CO2 out of the atmosphere with a direct air capture machine, the question is what to do with it.

JAN WURZBACHER: The big picture is taking one percent of CO2 out of the atmosphere within the next five to 10 years, that is roughly 400 million tons, and store it underground.

NARRATOR: Could we put carbon right back where we found it, underground?

STEVE PACALA: There are lots of rocks near the surface of the earth that would want to bond spontaneously with CO2. There’s enough of these kinds of minerals that you could remove all of the atmospheric CO2 many, many times over.

NARRATOR: One of the best places to try that out is Iceland.

SANDRA SNAEBJORNSDOTTIR: Here we are, the land of ice and fire. We have eruptions, we have earthquakes.

NARRATOR: Iceland is an island formed out of volcanic rock, called “basalt.”

SANDRA SNAEBJORNSDOTTIR: We see the basaltic mountains here around me and, actually, extending several kilometers downwards.

NARRATOR: Basalt is porous rock that readily bonds with CO2, over centuries. Sandra Snaebjornsdottir’s team has found a way to speed up that process.

SANDRA SNAEBJORNSDOTTIR: Carbfix is the method of capturing CO2 and turning it into stone. It’s magic, but it’s magic that already occurs in nature.

NARRATOR: Carbfix is turning one-third of the CO2 from this power plant into solid rock in less than two years. The key is water.

Inside this scrubber, gaseous CO2 is dissolved in water to react with basalt more quickly.

SANDRA SNAEBJORNSDOTTIR: This scrubber is actually just a giant SodaStream®.

NARRATOR: The fizzy water is then pumped into injection wells.

SANDRA SNAEBJORNSDOTTIR: This is actually my favorite part of it all; from here, the magic starts to happen. This pipe extends to over 2,000 feet, and there, we finally release this fluid to the rock.

NARRATOR: Once inside the basalt, the dissolved CO2 reacts with metals in the rock to form new solid minerals like calcium carbonate.

SANDRA SNAEBJORNSDOTTIR: Once we have injected the CO2 into the rock, it’s there forever.

NARRATOR: And Sandra is looking beyond Iceland. She is test-driving a direct air capture unit that can suck up CO2 anywhere.

SANDRA SNAEBJORNSDOTTIR: We don’t need the power plant. This can be done anywhere where you have a formation to store your CO2.

JANE LONG: What that means is you can go backwards. You can reverse the process of emitting carbon dioxide into the air.

NARRATOR: Negative emissions technologies like direct air capture could play a role in reaching net zero, the moment when humans remove as much CO2 from the atmosphere as they put in.

So, why isn’t this the ultimate answer to our CO2 problem?

JANE LONG: These technologies are very hard to scale up to a meaningful amount.

JAN WURZBACHER: The base module of our direct air capture plant, that’s a 40-foot shipping container.

In order to take one percent of global emissions out of the air, we would need 750,000 shipping containers.

NARRATOR: All to remove just half-a-gigaton of our annual emissions.

SCOTT DENNING: Direct air capture is very expensive, and it takes energy to suck CO2 out of the air. So, I hope you’re not imagining direct air capture vacuuming up the entire fossil fuel emissions of the world, because it ain’t going to happen.

NARRATOR: We’ll need lower-cost clean energy everywhere, before the promise of direct air capture can meet the scale of the problem.

LAB TECHNICIAN: M7 is on.

NARRATOR: So, some are exploring another idea: recycling our emissions.

LAB TECHNICIAN: Correction factor, zero point seven.

JANE LONG: We need to think about this problem very pragmatically. We can electrify a lot of things, but there’s certain parts of the energy system that are extremely hard to decarbonize.

STEVE PACALA: A good example is aviation.

JAN WURZBACHER: You couldn’t build, today, a commercial airplane for long distances which could fly on batteries. You would just carry way too much weight.

ALDO STEINFELD: This is physically impossible. There is no way around jet fuel.

JANE LONG: We need to be producing fuel that, when you burn that fuel, it doesn’t emit carbon dioxide.

ALDO STEINFELD: Remo, go ahead and rotate.

NARRATOR: Aldo Steinfeld thinks he’s found a way.

ALDO STEINFELD: Perfect. We are on target.

We have demonstrated that we can produce liquid hydrocarbon fuels from two ingredients: sunlight and ambient air. It may sound like science fiction or magic, but it is chemistry, is heat transfer, and also it’s a lot of engineering.

NARRATOR: Aldo captures CO2 and water from the air and feeds them into a solar reactor.

ALDO STEINFELD: Solar radiation is reflected and concentrated, at the focus, by a factor of 5,000. It is like the intensity of 5,000 suns.

NARRATOR: Concentrated solar energy drives a reaction that generates a synthetic gas, which can then be converted into fuels.

ALDO STEINFELD: And here, in my hands, I have an example of solar methanol.

NARRATOR: When it’s burned, the carbon in this fuel returns to the atmosphere. But since it was harvested there, the net CO2 is zero. This is called “carbon neutral,” and hundreds of scientists, like Aldo, are working to make carbon-neutral fuels a reality.

If they succeed, annual net emissions would drop by as much as one-billion tons.

ALDO STEINFELD: It’s going to be something revolutionary.

NARRATOR: But with these fuels up to six times the cost of standard fuel, it’s a revolution that has only just begun. But it raises the question: what else can we make by recycling CO2?

SCOTT DENNING: Carbon is this incredible building block. Think of it like those little, sort of, LEGO®toys that we used to have, only there’s four little plug-ins for it. So, you could bond carbon to carbon to carbon to carbon, to build all kinds of stuff.

CARBON XPRIZ: Imagine a world where everything around you is made from carbon emissions.

NARRATOR: This ad, from the XPRIZE Foundation, pitches a future where recycled CO2 shapes our world and a $20-million bounty to make that a reality.

MARCIUS EXTAVOUR (XPRIZE): We announced, “Hey, there’s a $20-million prize out there. We’re looking for innovators around the world. If you know how to convert CO2 into a useful material, consider entering this prize.”

We are trying to help catalyze the whole ecosystem of companies, of investors, of people that can deploy these technologies.

NARRATOR: The Carbon XPRIZE has brought five of the finalists here, to put their innovations to the test. They’re setting up shop next to a plentiful supply of CO2.

MARCIUS EXTAVOUR: They’ve got to take the emissions from a natural gas power plant and convert those into whatever material they like.

NARRATOR: From toothpaste, to yoga mats, to watches, each team will be scored on its net CO2 reduction.

MARCIUS EXTAVOUR: You could have a process that uses up a lot of CO2 to make its product, but in the end just produces more CO2 than it uses up. We don’t want that. We want things that actually are reducing CO2 overall.

APOORV SINHA: We just moved to site about two weeks ago. A day later, and I think we’d have snow in here that we’d be shoveling out.

NARRATOR: Apoorv Sinha is the C.E.O. of Carbon Upcycling Technologies, or CUT.

APOORV SINHA: We’re a carbon tech company, which takes carbon emissions and converts them into solid nanomaterial products, for use in anything from cutlery to car parts.

NARRATOR: But to make the biggest impact on CO2 and win this competition, Apoorv is focused on cement. Cement is an essential component of concrete, the glue that binds it together, but producing it creates a lot of CO2.

APOORV SINHA: Cement production accounts for over eight percent of the world’s annual emissions. If all the cement producing companies were a country, they would be the third largest emitter in the world.

NARRATOR: Apoorv’s process converts CO2 into a needed ingredient for concrete. And he believes it will also reduce the amount of cement that concrete manufacturers need.

He starts with an industrial waste powder, left over from burning coal, called “fly ash.”

APOORV SINHA: With the reactor that we have behind us, we’re scaling up and commercializing an enhanced fly ash, where the fly ash has been chemically activated to capture CO2.

As the reactor spins the fly ash, we inject CO2. Ball bearings coated with a catalyst speed up the chemical reaction. As the ball bearings rise and fall, the motion breaks up the fly ash and roughs up the surface so that more CO2 can be absorbed.

NARRATOR: As the CO2 penetrates the fly ash surface, it forges tunnels along the way. In effect, carbon dioxide has bonded with fly ash to create a nanoparticle with more reactive surface area, which can bind concrete together and strengthen it, with less cement.

APOORV SINHA: If concrete producers are able to use less cement in their production, they could considerably reduce the emissions that come from their industry.

NARRATOR: The question remains: is it strong enough for concrete makers to buy it?

NEIL: We just want to make sure that the technology is good and that it works really well.

APOORV SINHA: One of our local partners is a family-owned, Calgary-based concrete business called BURNCO.

NARRATOR: BURNCO is testing the strength of concrete held together using Apoorv’s nanoparticle.

BURNCO (Calgary District): When the cylinder breaks, we will have our final pressure, right up there.

NORM KUNTZ (BURNCO, Calgary District): These are impressive results. In normal production, you’re looking for changes of three to four percent, and these are showing results in double digits, which is very encouraging.

APOORV SINHA: We’re very confident that we can get up to a 10 percent reduction in the amount of cement used today. But our real target is to get that number up to 20 or 25 percent. Then we start talking about significantly moving the needle on the 37-gigaton-a-year number.

NARRATOR: But even if these new technologies can scale to their full potential, they could only lock away a fraction of our emissions.

DAVID KEITH: The total volume of CO2 that we create in the atmosphere is so much bigger than the volume of any products. I think people are losing track of the central issue, which is we have to reduce net CO2 emissions.

SCOTT DENNING: The easiest thing, believe it or not, is to burn less carbon, right? To, to not generate the CO2 in the first place.

NARRATOR: Carbon-free energy like wind, solar and nuclear power can drive down most of our annual emissions. And the rest could be offset with negative emissions technologies that remove CO2 from the air.

DAVID KEITH: We will do it. We will get to the day where there’ll be global celebrations, where we get to net zero, the day where we brought human CO2 emissions to zero. I think it’ll happen in my lifetime. It is doable. But on that day, we have not solved the climate problem. All we’ve done is stop making it worse.

NARRATOR: The problem that remains is heat.

SCOTT DENNING: The temperature of the earth is determined by heat coming in from the sun and heat going out, by radiation, out to space.

NARRATOR: Every single day, CO2 from our past emissions traps energy in the earth system, the same amount of energy as 500,000 of the bomb dropped on Hiroshima, detonating at once. That heat is altering our climate.

JANE LONG: What’s it going to be like when three months of the year are 115 degrees, when vast ecosystems have died out? People are going to push for doing something about this.

NARRATOR: And many fear Earth is approaching a tipping point that will trigger rapid change.

STEVE PACALA: The uncertainties that keep me up at night are what if we aren’t doing enough, and there is some monster lurking behind the door, that all of a sudden comes out into the world among us?

It’s a good idea that humanity has some sort of a backstop technology, something to do if we get surprised in a way that is very, very dangerous.

NARRATOR: Some think that backstop could be solar geoengineering.

STEVE PACALA: It’s a way to intercept sunlight coming into the planet, to cool the planet.

DAVID KEITH: The core idea is that humans might deliberately alter the earth’s energy balance to compensate for some of the warming and climate changes that come from greenhouse gases.

NARRATOR: Geoengineering the climate is a controversial idea, but nature can show us examples of where we might start: clouds.

SARAH DOHERTY (University of Washington): A cloud is just water condensed down into particles, into small droplets.

NARRATOR: These collections of droplets are, in effect, floating sun reflectors.

SARAH DOHERTY: Clouds play a huge role in controlling the climate, because they control the reflectivity of the planet, especially over the ocean. You go from sunlight hitting a very dark surface, where a lot of the sunlight is absorbed, to sunlight hitting an extremely bright surface, reflecting a lot of that sunlight back to space.

NARRATOR: Sarah Doherty of the Marine Cloud Brightening Project is working on a way to boost that effect.

SARAH DOHERTY: Can we add really small sea salt particles to clouds in a way that significantly increases their brightness? And do so over enough of the ocean that we would have a significant impact on the global temperature?

NARRATOR: But how do you make saltwater particles and launch them up into clouds?

SARAH DOHERTY: What we need is a nozzle like you’d see in a, sort of, a snowblower, except that the particles that we want to produce are about a thousandth the width of a human hair.

NARRATOR: So Sarah’s working with an engineer who knows all about machines for spraying superfine droplets, a concept developer of the earliest inkjet printers.

ARMAND NEUKERMANS: In a different life, I was an engineer and a physicist. I couldn’t enjoy retirement anymore and just sit there and watch what’s going on. Once you know what’s going to happen or might happen, you can’t sit down and say, “Yah, I’m just going to enjoy life.”

NARRATOR: Armand and his team of retired scientists have been developing a cloud brightening machine for over 10 years.

KATE MURPHY: They have been self-funding this research in borrowed lab space. PARC is a really good place for them, because of our history with aerosols.

NARRATOR: PARC, or Palo Alto Research Center, has infused the Marine Cloud Project with fresh expertise and cutting-edge tools.

Here, Kate Murphy can make aerosols from just about anything.

KATE MURPHY: This is our deep conditioner.

NARRATOR: Aerosols are tiny particles suspended in air.

KATE MURPHY: This is ketchup.

NARRATOR: For clouds, they’re not going to spray ketchup, but Kate can help the team design a nozzle for spraying saltwater.

ARMAND NEUKERMANS: Let me just give it a little water, okay?

NARRATOR: Kate’s expertise will help optimize the size and speed of the particles to propel them into marine clouds.

SUDS JAIN (Marine Cloud Brightening Project): So, you’re going to be redesigning the nozzle based on your computational fluid dynamics?

KATE MURPHY: Well, we hope to be able to understand the effect of multiple nozzles, so we would want to measure things like velocity and direction.

NARRATOR: These crisscrossed laser beams can help reveal whether Armand’s nozzle will hit the mark.

KATE MURPHY: The lasers are at power. It looks like our signal’s pretty good.

ARMAND NEUKERMANS: So, can you measure the vertical velocity? Do you have a measurement of that?

KATE MURPHY: Yes.

SARAH DOHERTY: PARC will be working on developing a full spray system. And then we would want to move outside, into real atmospheric conditions.

NARRATOR: On the other side of the world, outdoor research has already begun. Armand and the team have shared their insights with researchers in Australia, who are testing cloud brightening as a way to cool the waters surrounding the threatened coral of the Great Barrier Reef.

That project is targeted and local, but some estimate that cloud brightening on a global scale could offset all the heat trapped by our CO2 emissions.

SARAH DOHERTY: It’ll probably take a good 15 to 20 years to do all of the research involved with understanding how big of an effect we can have and, also, what all the side effects might be.

NARRATOR: Those side effects are not well understood and could include disruptions to ecosystems and rainfall patterns. Further research is needed.

SUDS JAIN: We have kids, we have grandkids. We’re doing it for their futures.

ARMAND NEUKERMANS: We are all in this together whether you have kids or not. We’re more than individuals; our society has to survive.

NARRATOR: We’re facing a problem that’s getting worse, not better. Do we need to consider more extreme measures?

FRANK KEUTSCH: In 15 years or 20 years, humanity may find itself at a point where impacts are so big that there is very large demand for fast action.

NARRATOR: To prepare, Frank Keutsch is starting now, by researching a controversial technology that goes further than brightening clouds. It would brighten the entire planet.

FRANK KEUTSCH: Putting particles in the stratosphere could reflect back some sunlight to space, reducing the amount of sunlight that hits the surface, and cooling down the planet.

NARRATOR: The effect would be immediate.

STEVE PACALA: We know this works, because every time a big volcano goes off and it injects aerosols into the stratosphere, the planet cools down.

SHEILA JASANOFF: That’s the idea behind solar geoengineering. It’s like drawing a curtain over the face of the earth.

FRANK KEUTSCH: The first time you hear about this, and you think, “Well, that sounds like a really bad idea. How could that not go wrong?” But what we’re doing to the climate as humans, that really, to me, starts seeming also quite scary and crazy and really worrying.

DAVID KEITH: The fact is the CO2 is in the atmosphere. Without a time machine, we can’t make it go away. We want to, in the long run, do carbon removal, but during the time that concentrations are high, we might want to do solar geoengineering to reduce the climate risk.

All that is hard mounted to us.

FRANK KEUTSCH: That is exactly what I was thinking.

DAVID KEITH: And then there is the balloon up there.

NARRATOR: Frank and David’s team is designing a first-of-its-kind experiment called SCoPEx to investigate the impacts of solar geoengineering.

JOHN: The only place I see that conversation getting sticky is where we do risk assessment on it.

FRANK KEUTSCH: If you put these particles out, what happens when these come back down? What happens when it gets into the environment? Are we endangering people?

DAVID KEITH: There are lots of things that we might need to know where the existing experimental background is bad. You actually have to go out and make measurements.

NARRATOR: The plan is to launch a 100-foot balloon into the stratosphere and release a plume of reflective aerosols.

FRANK KEUTSCH: We want to put out the particles of calcium carbonate, for example, and then go back through this plume and see whether the evolution of the air is the way we predicted based on our laboratory results. This is an experiment on a very small scale. And in fact, the amount of material we’re putting out is less than a normal airplane flight puts out.

NARRATOR: SCoPEx may be small, but many fear a large-scale manipulation of Earth’s atmosphere could trigger a cascade of dangerous, unintended consequences that ripple across the planet.

SHEILA JASANOFF: Nothing in our scientific capability actually enables us to understand the complexity of the interactions that would be set loose.

JANE LONG: It’s not just that it lowers the temperature, but what are some of the other effects on the hydrologic cycle or on heat waves and droughts?

SHEILA JASANOFF: This is a manipulation of the Earth’s atmosphere on a huge scale. What happens if things go wrong?

NARRATOR: SCoPEx is designed to start answering those questions, but there may be effects, beyond the physical, that no experiment can predict.

SHEILA JASANOFF: If we think that there’s this solution out there, then people may think it doesn’t matter if you’re polluting the planet.

DAVID KEITH: The root of the concern is that solar geoengineering research, however well-intentioned, will be used as an excuse for big fossil fuels to fight emissions cuts.

SCOTT DENNING: It’s just like a sci-fi dystopian novel or something, where we continue to just belch all this CO2 into the atmosphere, but, hey, it’s okay, because we’ve got these little umbrellas that are, you know, hiding us from the sun.

DAVID KEITH: Solar geoengineering does not get us out of the ethical and physical requirement to cut emissions.

NARRATOR: But with so much uncertainty, some think we’re better off investing in a different kind of machine, one developed in nature’s own laboratory, over millions of years and with a proven record of safely drawing down gigatons of CO2: trees.

LOLA FATOYINBO-AGUEH: When I’m going on a hike, through a forest, I have a tendency to look up and say, “Okay, oh, that tree’s about, 60 feet tall.” And then I try to calculate in my head, “Okay, how much carbon is stored in that tree?”

NARRATOR: Lola Fatoyinbo-Agueh is a research scientist at NASA’s Goddard Space Flight Center.

ATTICUS: Sweet, it has power. I love it when things work.

NARRATOR: She and her team are about to see these century-old trees in a new light.

LOLA FATOYINBO-AGUEH: There’s carbon all around us. If you think of trees as a machine, then trees would be a carbon capture machine. When we’re looking at trees, about half of that weight is carbon.

NARRATOR: Lola and her team want to know how much carbon is stored in this entire forest. To measure each and every tree, they’re using a special kind of tool: lasers.

LOLA FATOYINBO-AGUEH: We’re using a terrestrial laser scanner that shoots out billions of laser pulses every second and then measures the distance from the instrument to whatever is around it. The data that we get back generate a point cloud.

NARRATOR: Billions of data points form a 3D measurement of forest volume and the carbon stored within.

LOLA FATOYINBO-AGUEH: It’s so dense that it almost looks like a photograph. It’s like science-fiction.

NARRATOR: This scan may look like reality, but this is data. It reveals that in an area the size of a football field, these trees are storing roughly 150 tons of carbon, all pulled out of thin air. Which prompts Tom Crowther to ask, “Could we enlist trees in the race to draw down CO2?”

THOMAS CROWTHER (Swiss Federal Institute of Technology Zurich [ETH Zurich]): Our lab is urgently trying to figure out how we increase the area of forest across the globe, to capture as much carbon as we possibly can, in the fight against climate change.

NARRATOR: Tom’s findings began with a surprising discovery.

TOM CROWTHER: We thought there was around 400-billion trees on the planet, but we showed that there is, in fact, around three-trillion trees. There’s more trees on the surface of our planet than there are stars in the galaxy.

NARRATOR: The big question is how many more trees could we add?

CONSTANTIN ZOHNER (Swiss Federal Institute of Technology Zurich [ETH Zurich]): In order to understand the global forest system we need to map a lot of things, we need to know where forests are, where forests could be.

TOM CROWTHER: We collect our data from millions of locations around the world, where scientists have been on the ground, evaluating those ecosystems.

NARRATOR: Data like leaf-fall patterns in forests around the world...

CONSTANTIN ZOHNER: I’m trying to understand the seasonal rhythm of plants.

NARRATOR: …microscopic organisms, like the tiny worms that feed the soil beneath the trees...

JOHAN VAN DEN HOOGEN (Swiss Federal Institute of Technology Zurich [ETH Zurich]): In just this clearing, there is millions and millions of nematodes living in the soil.

NARRATOR: …and decades of satellite data on factors like rainfall and temperature.

DEVIN ROUTH (Swiss Federal Institute of Technology Zurich [ETH Zurich]): When I look at ecosystems, most of the time I’m looking from the top down.

TOM CROWTHER: And with all of that data, we can start to see the patterns across the globe. Using remote sensing information from satellites and machine learning technologies, we can generate maps that can predict which regions can support new trees and which ones cannot. This really is a data revolution.

NARRATOR: The detail is astonishing. And the potential for new forests is vast.

TOM CROWTHER: Outside of urban and agricultural areas, there’s room for about 2.5-billion acres of forest.

CONSTANTIN ZOHNER: The area we identified equals the size of the United States. So, there is a huge area available for restoration.

NARRATOR: Enough space for 1.2-trillion new trees, all sucking CO2 out of the air.

TOM CROWTHER: If we were to restore a trillion trees, the right types of trees in the right kinds of soils, and have them grow to full health, they could store an additional 205-gigatons of carbon.

NARRATOR: To put that into context: we’ve released nearly 660-gigatons of carbon into Earth’s systems since human industrial activity began.

TOM CROWTHER: Restoring global forests and conserving the vital forests that we currently have could take a huge chunk out of that excess carbon. This is a really massive carbon drawdown solution. We knew that this was going to make an enormous splash.

NARRATOR: But these findings also made waves.

LOLA FATOYINBO-AGUEH: That study is causing a lot of debate. On the one hand, a lot of people are talking about the potential of restoration of forests. On the other hand, I would say that a lot of people are very upset about it. The uncertainty around the amount of carbon that’s stored in trees is so high that we can’t really make any informed recommendations on how many trees we need to plant.

NARRATOR: Lola wants to use new technology from NASA to fill those areas of uncertainty with hard data.

LOLA FATOYINBO-AGUEH: We have over 20 Earth-observing satellites right now, from NASA alone, looking at our Planet Earth. But what we’re seeing is all in two dimensions. What we’re missing here is the third dimension.

NARRATOR: Enter a powerful new tool called GEDI. With the same laser technology used in her terrestrial scanners, Lola can get a 3-dimensional measure of forest carbon from the international space station.

LOLA FATOYINBO-AGUEH: GEDI stands for the Global Ecosystem Dynamics Investigation, which is what you’re seeing, right here. This is about the size of a fridge. You can see the laser shooting down out of the bottom of the instrument, towards the surface of the planet. We actually can see a full profile of plant materials.

The game changer here is that this is going to be, for the first time, a near-global dataset.

NARRATOR: GEDI will give clearer insight on the carbon new forests could store. But equally important, it can pinpoint the old forest carbon we must preserve.

LOLA FATOYINBO-AGUEH: Forests are really important for our water supply; forests protect us from heat; forests breathe, they breathe, in some ways, just like we do. When you lose a lot of the ecosystem services that forests provide, that has a direct impact on the wellbeing of people.

NARRATOR: But on an increasingly populated planet, trees are not the only living things competing for land.

STEVE PACALA: We already use all of our agricultural land to feed our existing population, and over the next 30 years, food demand is going to double. If you take land to solve the climate problem, you create another problem.

NARRATOR: Is there a solution that can solve more than one problem at a time?

WHENDEE L. SILVER (University of California, Berkeley): Some people are looking at ways in which forests can help slow climate change. Our research is somewhat different in that we’re looking at grasslands.

I want to have enough so that we can do experiments.

NARRATOR: In California, Whendee Silver is looking for a way to pull down CO2 right where we grow our food, Earth’s grasslands.

WHENDEE SILVER: This is a classic, beautiful annual grassland. Grasslands grow in places where there’s drought for part of the year. And these grasses have developed great tools for getting water, particularly by growing more roots. And any time plants invest a lot of their energy into roots, it’s like injecting carbon into the soil.

NARRATOR: But tilling releases that carbon and degrades the soil. And producing our food creates even more problems.

WHENDEE SILVER: We all eat food every day. We have to grow that food. And we create a lot of organic waste in the process.

NARRATOR: When organic waste sits in a landfill or slurry pond, it creates an oxygen-deprived environment, favorable to certain microbes, which, in turn produce methane, a greenhouse gas 34-times more potent than CO2.

WHENDEE SILVER: We’re trying to tackle three big problems: waste, degrading soil health and climate change. We came up with something relatively simple: composting.

NARRATOR: In composting, food waste is regularly turned, adding oxygen to the mix and keeping the methane-producing microbes at bay.

WHENDEE SILVER: It creates this organic and nutrient-rich resource, like a slow release fertilizer that helps plants grow.

NARRATOR: By turning a waste into a nutrient, compost can boost plant growth and potentially turn vast stretches of Earth’s food crops into a carbon-storing juggernaut.

WHENDEE SILVER: We now have 10 years of data, showing that just a one-time dusting of compost onto the soil surface can have a long term impact on plant growth and increase carbon storage in soils.

NARRATOR: Whendee’s research shows that a single layer of compost can increase plant growth by up to 78 percent and increase soil carbon by up to 37 percent, for three years.

WHENDEE SILVER: The real challenge is to extrapolate from little tiny soil samples in the field, to big chunks of California or the globe. That’s a huge challenge.

NARRATOR: As the hunt for solutions continues in the decades ahead, stopping our emissions remains the most urgent challenge of today.

DAVID KEITH: If we really didn’t do anything to limit carbon emissions, we would have climate changes as big as the changes from the glacial to interglacial state and do that in one human lifetime with huge potential impacts.

SCOTT DENNING: The more of a mess we make, the bigger of a mess we’ll have to clean up. We, today, get to decide whether to continue along this path or to dramatically shift our economy off of coal, oil and gas.

MARCIUS EXTAVOUR: Every big transformative solution starts small. It starts with a couple people talking. They make a small version. They make a bigger version, and more people pile in.

CONSTANTIN ZOHNER: This is one solution, but we need thousands of solutions, if we want to tackle climate change.

WHENDEE SILVER: There’s no one magic silver bullet that will solve this problem.

APOORV SINHA: The main challenge that we have is that these transitions don’t happen overnight.

SANDRA SNAEBJORNSDOTTIR: We have the tools already, but we really have to start moving.

SCOTT DENNING: We need better transportation systems. We need solar power and wind power and water power and probably nuclear power. We need to plant trees. We need to manage our farms better. We need direct air capture. I think we probably need it all.

JANE LONG: We have to start really looking at what can scale up and be maintained for decades, if not centuries. That’s the challenge here, but it’s an incredibly important challenge.

STEVE PACALA: Fifteen years ago, no one would have predicted that the emissions in developed countries around the world would be dropping. Not fast enough yet, but that gives me hope and should give everyone hope that with the combined might of human ingenuity we can actually solve this problem.

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