Bold, almost reckless: Israeli scientists seek to block solar radiation in a radical climate experimen

On June 8, 1783, a 25-kilometer-long fissure opened in Iceland, unleashing the eruption of about 130 volcanic craters. For the next eight months, lava shot from the earth in fountains reaching 800 meters high. Around 120 million tons of sulfur dioxide poured into the atmosphere, obscuring the sun. Nearly a quarter of Iceland's population died, along with most of its livestock.

One eyewitness, the pastor Jón Steingrímsson, described the unfolding catastrophe in an account recalled by Scientific American: "First the ground swelled up with tremendous howling, then suddenly a cry shattered it into pieces and exposing [the Earth's] guts, like an animal tearing apart its prey."

The effects reached far beyond the small North Atlantic island. Sulfur particles rose into the stratosphere and traveled on atmospheric currents across the Northern Hemisphere, forming a veil that altered the global climate. Monsoons in India and Africa weakened dramatically, while one-sixth of Egypt's population died of starvation due to the dwindling Nile. Europe and North America had an exceptionally harsh winter. The Mississippi River froze as far south as New Orleans, and ice floes drifted through the subtropical waters of the Gulf of Mexico. Scientists estimate the eruption lowered average temperatures across the Northern Hemisphere by about 1 degree Celsius.

Ice floes with penguins floating through the Gulf of Mexico may sound like an appealing vision in today's warming world. But achieving it, perhaps, does not require a catastrophic volcanic eruption.

A small company based in Nes Tziona, in central Israel, believes it has another way. Its ambition is nothing less than to dial Earth's temperature back to pre-industrial levels through advanced climate engineering. To do that, the company has developed a particle that, if dispersed in the stratosphere in quantities of millions of tons, would reflect most of the incoming solar radiation that hits them back into space – much like a tiny mirror.

The technology is groundbreaking. The promise is enormous. And so are the risks.

If artificial intelligence seems like humanity taking one step too far in its quest to play God, Stardust Solutions pushes the idea even further. On paper, its proposal sounds almost insane. Yet behind it stands a team of respected scientists. The company has already raised $75 million, making it by far the world's most successful solar geoengineering startup. Investors include the Canadian-Israeli venture capital fund Awz Ventures, whose founders and advisers include former senior officials from Israeli intelligence, the Mossad, Shin Bet security service, and their counterparts at the CIA, FBI and MI5.

The latest Israeli attempt to reshape the world is not on a disputed stretch of land in the Middle East but in the Earth's atmosphere itself. Depending on whom you ask, the project could help save humanity or push it closer to catastrophe. It is already attracting global attention.

About a month ago, the company published eight papers online describing the project for the first time, generating intense interest. Interview requests have poured into its offices in Nes Tziona from major newspapers and television networks across the world, from Australia and East Asia to North America. Haaretz is the first Israeli media outlet to visit the company's laboratories for an open, if not always easy to follow, conversation with its three founders.

Dozens of research groups at universities around the world are exploring ways to cool the planet by injecting tiny particles, or aerosols, into the stratosphere, where they would reflect part of the sun's radiation back into space. A team from Cambridge University and Harvard University, backed by the British government, plans to send a drone into the upper atmosphere next year to test light-reflecting particles.

Nearly everyone in the field focuses on sulfates – the same material released during volcanic eruptions. The logic is clear: Scientists know sulfates reduce global temperatures, and they also understand their drawbacks, including damage to the ozone layer and the risk of warming parts of the stratosphere. Stardust chose a different material, one it believes can provide the same cooling effect without those costs.

The company was founded three years ago by Prof. Eli Waxman, a theoretical astrophysicist and head of the Particle Physics and Astrophysics Department at the Weizmann Institute of Science, who also served as chief scientist of the Israel Atomic Energy Commission during the negotiations that led to the 2015 Iran nuclear agreement under the Obama administration; Dr. Yanai Yedvab, who served as Waxman's deputy at the commission; and Amyad Spector, a former physicist at Israel's Negev Nuclear Research Center in Dimona.

We meet for a four-hour marathon conversation at the company's offices in the well-maintained Nes Tziona Science Park. The spacious conference room is large enough to hold all 25 of the company's employees, including chemists, aerospace engineers, physicists and nanotechnology experts. Across the hall, a chemistry laboratory is developing the particle that its creators hope could help save humanity. Farther down the corridor, an experimental physics lab is working on methods to monitor the particle, in case it decides to cause harm instead. In a nearby building, another lab houses a test chamber where engineers are developing the system that would disperse the particles into the stratosphere, a challenge with life-or-death implications.

The story began during the COVID-19 pandemic, explains Spector, the youngest of the three founders: "Everything we were doing stopped, and suddenly we had an opportunity to think about how to get out of the mental bubbles we were living in."

"Naively, we started thinking about climate," Yedvab says, jumping in. "It felt like a huge problem that combined scientific and technological questions with decision-making and public policy, which were exactly the kinds of issues we had dealt with at the commission."

So a few physicists, with unexpected free time, decided to solve the climate crisis?

"The first person to propose addressing climate change by dispersing particles in the atmosphere was the physicist Edward Teller," Waxman says. "Teller was one of the leaders of the American nuclear program, Oppenheimer's nemesis, if you remember the movie. So he was a physicist, a Jew, and a member of the Atomic Energy Commission. In other words, someone a lot like us."

For six months, the three nuclear scientists met and learned about the new field.

"We had a kind of thinking club," Yedvab recalls. "We debated the fundamental questions. At that stage, we weren't even thinking about starting a company. We realized the climate crisis was getting worse and that the costs could become unbearable, and that the existing solutions weren't providing an answer. Reducing emissions and developing better renewable energy are essential, but we concluded they probably wouldn't be enough. Humanity would need another complementary tool."

"That's how physicists work," Waxman says. "We approach problems methodically. For example, we looked at carbon capture and concluded that it doesn't solve the problem. But Teller's idea does."

The concept has existed ever since Teller published his influential paper in 1996, when he was 88 years old. Yet little has changed. "We realized that for 30 years the research community has focused on sulfates," Waxman continues. "One group studies the sulfates themselves, another how they disperse in the atmosphere, and a third how they affect wind patterns. But no one had precisely defined the overall problem and worked backward to develop a complete solution."

"In every scientific field, researchers naturally begin with basic science," Yedvab explains. "That happened here too. Starting with sulfates also made sense because they were already well understood. But at some point, you need to shift to systemic thinking – to connect the Lego bricks. That simply hadn't happened. Quite a few people abroad told us that an initiative like this probably could not have started anywhere except Israel."

Waxman: "Israelis have an exceptional ability to challenge conventions and do things differently."

Yedvab: "When we started there was no particle, no delivery system, no algorithms, no monitoring system. Most startups solve a single problem. We had to imagine an entire chain of technologies, invent every component before we even knew what it should look like, and convince the world that this was a good solution. At a time when Israel's international image is less than optimal, creating positive leadership in a field that addresses a global problem could be significant."

Or, people might say: The Israelis are making trouble again, dispersing particles into the atmosphere while making money from it.

"Israelis aren't going to disperse anything," Waxman replies. "We'll make the technology available to humanity. Humanity may ultimately decide it doesn't want it, but that decision won't be ours."

"The problem is global," Yedvab says. "The solution will have to be global as well. It will require agreement among many countries. At the same time, we're proud that the technology was developed in Israel."

The idea of deliberately altering the atmosphere is highly controversial. In 2022, more than 600 scientists signed off on a call for an international moratorium on such efforts. Several U.S. states have already banned forms of climate engineering, and in February, Republican Congressman Greg Steube introduced legislation that would prohibit weather modification.

No one knows with certainty how solar geoengineering will affect weather patterns, food supplies or even global politics. Many scientists argue that it will take years of additional research before it is possible to determine whether the technology's benefits outweigh its risks, which could be catastrophic. Climate models suggest, for example, that the approach could reduce rainfall in parts of Africa, alter monsoon patterns and intensify hurricanes in the North Atlantic. Yet Earth's climate system is extraordinarily complex, and existing models have only limited ability to predict the consequences of an intervention on this scale.

Even if the technology proved beneficial overall, some countries could still suffer. What, for example, would happen if monsoon rains in India diminished and the country demanded that the program be halted (a scenario explored in the book "The Collapse of Western Civilization: A View from the Future")? An abrupt end after years of deployment could trigger what scientists call "termination shock": a rapid surge in global temperatures that could itself be catastrophic.

And what if, while the technology was in use, another massive volcanic eruption like Iceland's in the 18th century occurred? The list of possible disruptions and disasters is too long, and we only have one Earth on which to test them. But this is also the Earth we are steadily destroying.

Despite advances in clean energy, greenhouse gas emissions continue to rise. In a 2022 report, the Intergovernmental Panel on Climate Change, aka IPCC, concluded that humanity is already locked onto a path toward more frequent and intense heat waves, megafires, floods and droughts. Coral reefs around the world are expected to collapse, and diseases and agricultural pests could spread. These phenomena are expected to worsen with rising temperatures, which will almost certainly lead to the extinction of many animal species, water and food-related crises, widespread migration waves and growing instability and conflict around the world.

Perhaps, then, we no longer have a choice but to bet on climate engineering.

Since the Industrial Revolution, humanity has continuously pumped carbon dioxide and other greenhouse gases into the atmosphere. Together, their warming effect is equivalent to about 1 percent of incoming solar radiation.

"If we block 1 percent," Waxman says matter-of-factly, "we return to the pre-industrial era."

His comment sends a pleasant shiver down the spine. For a moment, it all sounds simple. Maybe we really can turn back the clock and have our cake while keeping it cool.

"The challenge is doing it without causing negative impacts," he adds, bringing the conversation back to reality. Still, he believes that may be possible. And argues that the particle developed by Stardust could make it possible. But not everyone agrees.

Ben Kravitz, an associate professor in the Department of Earth and Atmospheric Sciences at Indiana University, has extensively researched the potential effects of solar climate geoengineering.

"Stratospheric aerosol injection is probably the most studied idea in climate intervention," Kravitz told Haaretz. "The most common choice of aerosol is sulfate, which mimics a large volcanic eruption. There are downsides to that, and we know there are downsides because we've seen volcanic eruptions in nature. But because of those eruptions, we also know the idea would probably work.

"Stardust is proposing to use calcite with a silica coating, according to its papers. We've never seen any amount of that in the stratosphere, so there are huge unknowns. We don't even know if it would work the way they say it would, and there are enormous potential risks. Stardust's papers claim that this material is attractive because of its 'chemical inertness in the stratosphere' and 'biocompatibility,'" Kravitz continued.

"As far as I can tell, these claims are untested, and there is strong evidence suggesting they may not be true. With sulfate aerosols, even if you don't like the idea, we have enough information to have an informed discussion about the potential benefits and risks. With this proposed designer particle, we'd be doing little better than guessing."

"There is a difference between what a company says it wants and what it actually does," Kravitz concluded. "I caution people against believing what Stardust says without strong evidence. If Stardust is genuinely interested in building trust and fulfilling a social contract, it still has a long way to go."

Suspicion toward Stardust has grown within the academic community after several years in which the company's team worked in secrecy. The founders say the publication of their recent series of papers marks a change of direction. In one of the eight papers, the researchers outlined what they believe should be the minimum safety requirements for any solar geoengineering technology.

The first is biological and environmental safety. The material must not harm humans or other living systems, and once it returns to Earth, it should decompose rather than accumulate in the environment like microplastics. The second requirement is that it must not damage the stratosphere or the ozone layer. The third is that it must not trigger other climatic changes as an unintended consequence of reducing incoming solar radiation.

"These principles guide our work," Yedvab stresses. "But regulation must, of course, be established by governments and international bodies. Right now, there is no regulation in this field, and we hope the proposal we presented to the scientific community will encourage discussion and help move the issue forward."

The researchers began by searching for naturally occurring materials with the right optical properties. They needed a substance that could reflect solar radiation while remaining transparent to visible light. In other words, it could not absorb light and heat up itself. Not surprisingly, there are very few materials that meet those criteria. Fortunately, nature provides a handful.

The researchers identified five candidates, one of which stood out as especially promising: an amorphous silicon dioxide particle, better known as silica. It just might save the world.

Kravitz is also skeptical about the particle's biological safety. He points to the lung disease silicosis, which is caused by inhaling silica dust and is common, for example, among miners exposed to it. "If you want to scare yourself, look up silicosis and then imagine megatons of silica-bearing particles being injected into the upper atmosphere," he said.

The Stardust team insists there is no cause for concern. "Silicosis is caused by silica with a different chemical structure, one with sharp edges," Spector says. "Our particle is amorphous and smooth. Nature produces it in algae and plants, and it's already used in food additives."

Spector opens his laptop and searches Google. "Seeing is believing," he says, pulling up a 2016 Fox News report on experiments conducted by the U.S. Department of Homeland Security. As part of a study of airflow in the New York subway system, researchers dispersed the same material throughout subway stations and tunnels while commuters moved through them.

"The purpose was to study how air flows through the subway," Spector says. "They used our material because there's nothing hazardous about it. They simply dispersed it in stations and tunnels."

Would you let your own children breathe the particle?

"The material comes in bags that I transport to the lab in my own car. Some of it has already spilled inside, and that's the same car my children ride in."

To examine the particle's effect on the stratosphere, the researchers exposed it in the laboratory to the ultraviolet radiation and gaseous conditions that prevail at those altitudes.

"The work is still under review," Waxman says. "But based on our lab experiments, we found that the particle remains unchanged under stratospheric conditions, consistent with the requirements we established." Nor should people on the ground notice its presence. Reducing incoming solar radiation by about 1 percent would be virtually impossible to detect with the naked eye, he says, adding, "Natural variations during the day, for example, because of cloud cover, are much larger."

One of the biggest engineering challenges is simply getting the particles into the atmosphere. Tiny particles naturally tend to clump together, forming larger particles that are unsuitable for dispersion.

"This is a major problem, and perhaps one reason other researchers haven't pursued this approach," Waxman says. "Our chemical engineers developed a manufacturing process that uses high-temperature heating and attaches molecules to the particle's surface, preventing it from reacting with neighboring particles."

The particles would be released from aircraft equipped with a specialized dispersion system, which would release them in trails behind the aircraft.

From a safety perspective, the most complex aspect is determining whether the technology could produce unintended climatic effects, as a large-scale field experiment cannot be carried out at the outset. Researchers therefore have to rely heavily on climate models, which inevitably contain substantial uncertainty.

To reduce dependence on models, Stardust has developed what it describes as a novel monitoring system. Each particle would be tagged individually, allowing researchers to track their movement through the atmosphere using instruments carried by balloons and drones. Simultaneously, satellites would measure changes in Earth's radiation balance and monitor any heating of the stratosphere.

The plan is to begin by dispersing a relatively small quantity of particles, and then to observe how they spread and affect the stratosphere.

Yedvab: "It's similar to clinical trials in the pharmaceutical industry. You start with a small number of participants and test for safety. There are clear criteria for success, and if they're met, you expand the trial and gradually collect more information. We would do the same: start with quantities so small that they have no environmental or health impact. If the results meet the criteria, we would proceed step by step.

"There will be a multiyear process aimed at gathering data and calibrating models, before approaching dispersion levels large enough to affect the climate. That way, we would never suddenly cross into unknown territory. At every stage, the process could be stopped or modified."

The researchers argue that this gradual approach is one of their particle's biggest advantages. According to them, sulfates do not allow for such small-scale testing because the stratosphere already contains hundreds of thousands of tons of naturally occurring sulfate. Any experiment would therefore require releasing a large additional quantity to produce measurable results. Sulfates also react chemically with other atmospheric compounds, whereas Stardust says its silica particle remains chemically inert.

Most research in solar geoengineering takes place within universities and public research institutions. Stardust, by contrast, is a private for-profit company. That, too, fuels some of the suspicion surrounding it.

"It wasn't obvious that we would become a company," Yedvab admits. "We explored several options. In the end, we chose this path because when you look at technologies that have benefited humanity, whether in medicine, space exploration or dozens of other fields, many were developed by private companies. That's where it's possible to raise significant resources and attract talented people."

I assume no pharmaceutical company began with bad intentions. But commercialization creates incentives. Eventually, even if you've developed something as harmful as opioids, there's enormous pressure to sell it.

"There are pharmaceutical companies that have had a positive impact, and others that have done harm," Yedvab explains. "We were very careful to choose investors whose goals aligned with ours. Our lead investor is the Lowercarbon Capital, in California. We had dozens of conversations with them. If their priority had been commercialization at any cost, we would not have partnered with them. We had other options."

He says that commitment extends throughout the project: "If, at any point in the development process, we conclude that the technology doesn't work or isn't safe, we'll walk away from it. We will not take part in irresponsible deployment. We told our investors that from the outset, and we continue to remind them. For all of us, this is a second or third career. We have children, and we want to leave them a world that is at least as good as the one we inherited. We're idealists."

Facebook also began as a platform meant to strengthen social connections. OpenAI started as an open-source company. We've seen this story before. Here, we're talking about a private company that hopes to release millions of particles into the atmosphere.

Spector: "It's much harder to control artificial intelligence. AI is just code. Anyone can run it. Something like this can't happen without governments approving it. Investors understand that the client is many countries together."

"Our approach is transparency," Yedvab adds. "Look at the papers we've published. Everything is public, including the particle's composition. Anthropic doesn't publish its code. We have agreements with researchers at 20 universities in Israel and abroad, and those agreements require both sides to publish all research findings. No cherry-picking."

He cites a few scientists who have joined the effort: "Prof. Vicki Grassian from the University of California San Diego, one of the world's leading atmospheric chemists, is working with us. She has four postdoctoral researchers working full time on our particle. Prof. Piers Forster from the University of Leeds, lead author of the last two IPCC reports and one of the world's foremost climate scientists, is also working with us."

In correspondence with Haaretz, Forster said he was impressed that the three physicists are sincere and open about what they are doing.

"I am keen to encourage open research generally," he wrote. "Stardust have built up a lot of knowledge. I was keen to get as much of it into the public domain as possible, so their science can be thoroughly investigated by a wider research community. I think the biggest risk is that a lot rests on their particle being chemically inert. So it's good that they have put its details in the public domain so it can be thoroughly tested."

Even if Stardust's particle proves to be chemically inert and the technology works well, lowering global temperatures would not solve some of the most serious consequences of climate change. Ocean acidification would continue, as would air pollution, because greenhouse gas emissions would not stop. In fact, emissions could even accelerate if cooler temperatures reduced the urgency to cut them.

"We're buying humanity time," Yedvab says, "a few decades during which all those other problems will still have to be addressed. The point is that without this solution, we'll face not only the problems you mentioned, but an increasingly catastrophic combination of extreme climate impacts."

So humanity would become dependent on your technology. If particle dispersal continued for decades while greenhouse gases kept accumulating, stopping the program could trigger a sudden spike in temperatures.

Yedvab: "The idea is to integrate this approach with other solutions. I'm convinced those solutions will emerge because there are already strong incentives to develop cheap, clean energy. Eventually it will happen, but it may take a few decades. And we are here to bridge that gap. But it is true that over decades, our technology will probably need to be implemented. It would have to be phased out very gradually to avoid termination shock."

Or you'll buy humanity a few extra decades, and humanity, as usual, will waste them.

"It's like treating a critically ill patient. First you stabilize them, then you address the underlying disease. Our assessment is that we'll need to deal with this acute problem in the coming years. We don't want to reach that point and ask ourselves, 'Why didn't we develop a tool that could stabilize the patient?' The main reason we founded Stardust is so governments will have an option 15 years from now. That's our goal. Decisions about whether to deploy this technology will ultimately be made by governments."

"Look at what happened during COVID-19," Spector adds. "If BioNTech, which is also a commercial company, hadn't already done the research, we would have needed several more years after the pandemic broke out. What we're doing is very similar. In both cases, governments decide whether to use the technology and how to regulate it."

Today's governments are heavily influenced by powerful economic interests. They don't always act in the public interest. It's easy to imagine the conspiracy theories that would emerge if your technology were ever deployed.

"We're developing the best technology we can within the limits of what we control," Yedvab says. "As part of that process, we've tried to understand the public's main concerns. One of them is the possibility that a private company could influence decisions in ways that don't serve the public interest. So, our position is unequivocal. There must be an iron wall between those who develop the technology and those who decide whether to use it."

According to published reports, you've hired lobbyists in Washington at a cost of hundreds of thousands of dollars.

Yedvab: "When we meet with policymakers, we're not asking for funding or special treatment for Stardust. Rather, we're urging them to establish regulations that define what is and isn't permissible. This is part of our responsibility as pioneers in the field. We tell decision-makers that the technology we're developing could mature within a few years and that, in the coming decade, we may need to stabilize Earth's temperature to prevent severe climate impacts. In light of this, we believe it is their responsibility to seriously begin developing regulations to govern the field."

Why are some scientists suspicious of you?

"There are people who've worked on this for 30 years," Waxman replies. "Then we came in from outside the field with an approach that's different from what the entire community has been pursuing. If there were no resistance, that would be surprising. Or it would mean we weren't doing anything interesting.

"In the papers we published," he adds, "it was very important for us to expose our work to the judgment of the scientific community. So far, no criticism has identified a flaw in either the proposed solution or its underlying logic. That strengthened our confidence that we're on the right track. In the end, this is a question of weighing risks.

"Humanity is already conducting an enormous uncontrolled experiment by releasing tens of billions of tons of greenhouse gases into the atmosphere every year. No one controls that, and no one can accurately predict the consequences. If we release our material, there are uncertainties, but they are inherently much smaller than the consequences created by what is already being done. And unlike greenhouse gas emissions, our technology allows us to deal with these uncertainties through a phased testing mechanism. And we know it will also do good things."

The company estimates it will complete development of its system within three to five years, giving governments enough information to begin making policy decisions and establishing regulatory frameworks. Reaching full operational capability within 10 to 15 years would require an enormous industrial effort. Factories would have to produce roughly 2 million tons of the particle each year. A fleet of several hundred aircraft would need to operate around the clock, every day of the year. And a global monitoring network of balloons, drones and satellites would continuously track the particles and their effects.

That operation sounds like a significant source of emissions in its own right.

Waxman: "Compared with current global emissions, it's negligible. Especially relative to the cooling effect it would produce. Our particle is about a million times more effective than greenhouse gases. In other words, 1 gram of a Stardust particle offsets the warming effect of roughly 1 ton of greenhouse gases."

And the price? A bargain. "To stabilize Earth's temperature, we estimate the cost would be about $20 billion a year," Yedvab notes. "This is negligible, compared with the economic damage caused by climate change. Climate-related losses are already estimated at hundreds of billions of dollars annually and, by conservative estimates, could reach $2 trillion to $3 trillion a year by 2050. Not all the questions you've raised have answers today, and many different players will have to cooperate for this to work. But providing a good, effective alternative to what humanity is doing seems a good use of our time here."

Prof. Douglas MacMartin from Cornell University, a solar engineering researcher for over 15 years, oscillates between admiration and suspicion, between anger and hope, on this subject.

"I think it's absolutely great that there are new people with new ideas," he said during a Zoom interview. "I think it's great that they're exploring alternative materials. My problem is when they mislead people about the relative advantages of what they're doing compared with sulfate, and about how mature their technology really is."

MacMartin argues that the main drawbacks of using sulfate are stratospheric heating, damage to the ozone layer and the formation of acid rain. In his view, however, those problems are relatively modest. The biggest problem, he says, is that when Earth is warmed by one mechanism and then cooled by another, it does not simply return to its original state. Even if global temperatures were restored to their levels at the beginning of the 19th century, Earth will never regain its youth.

What Earth would actually look like after large-scale cooling is a question that, according to MacMartin, is largely independent of the type of aerosol used. The same is true of many potential climatic side effects, including changes in rainfall patterns. Those consequences arise primarily from reducing incoming solar radiation itself, not from the specific material chosen to reflect it.

"They're trying to sell their special material as if it's far better than sulfate, but it's not really fixing anything and instead adds a lot of uncertainty," the professor argues, referring also to the possibility of people breathing it. "So I think the answer is: We don't know. Let's say you're a head of government five or 10 years from now, and you decide, 'All right, I think we should deploy stratospheric aerosol injection. What material are we going to choose?' There are multiple options on the table. If someone said, 'I've got a material that eliminates those side effects, but it's never been in the stratosphere, and we really don't know what it'll do,' which one am I going to pick? My guess is it's still going to be sulfate."

Let's leave aside the competition between sulfate and silica, or another particle that might be developed someday and proven to be the best. Are you essentially saying that humanity has a solution?

MacMartin: "People find the idea terrifying. And, you know, it is. But climate change is probably worse. So we should take stratospheric aerosol injection seriously. Most of the impacts of climate change are driven by temperature, and we know how to cool the planet."

There are other challenges, including "some actual engineering to be done," such as developing aircraft capable of reaching the stratosphere and systems for dispersing the particles. But those, MacMartin says, are engineering challenges that could be solved within five to 10 years.

"The biggest challenge," he declares, "is that this affects 8 billion people. How on earth do you make decisions on behalf of 8 billion people? Even if all the science said this would be better for everybody on the planet, is everybody on the planet going to believe that science? Is everybody on the planet going to believe the motivations of whoever chooses to use it?"

The moment is approaching when humanity can no longer continue with business as usual: more flights, more cars, more data centers, more meat consumption, endless consumerism, political leaders burying their heads in the increasingly hot sand, and the relentless pursuit of profit by giant corporations.

The sword will no longer be merely hanging over our heads. It will be embedded deep in the flesh.

Something will have to be done. Humanity is so stubborn that it sometimes seems it would prefer to keep emitting and die rather than stop emitting at all. And yet, there may still be something we can do.

On the eve of another hellish summer, courtesy of our greenhouse gas emissions and El Niño, that offers half a measure of comfort – and half a measure of dread.