Scatter, Adapt, and Remember: How Humans Will Survive a Mass Extinction

by Newitz, Annalee

  So it’s possible that algae will be helping us in our geoengineering projects. Another possibility is that we’ll be enlisting the aid of rocks. One of the most intriguing theories about how we’d manipulate the Earth into pulling down carbon was dreamed up by Tim Kruger, who heads the Oxford Martin School’s geoengineering efforts. I met with him across campus from Driscoll’s office, in an enormous stone building once called the Indian Institute and devoted to training British civil servants for jobs in India. It was erected at the height of British imperialism, long before anyone imagined that burning coal might change the planet as profoundly as colonialism did.

  Kruger is a slight, blond man who leans forward earnestly when he talks. “I’ve looked at heating limestone to generate lime that you could add to seawater,” he explained in the same tone another person might use to describe a new recipe for cake. Of course, Kruger’s cake is very dangerous—though it might just save the world. “When you add lime to seawater, it absorbs almost twice as much carbon dioxide as before,” he continued. Once all that extra carbon was locked into the ocean, it would slowly cycle into the deep ocean, where it would remain safely sequestered. An additional benefit of Kruger’s plan is that adding lime to the ocean could also counteract the ocean acidification we’re seeing today. Given that geologists have ample evidence that previous mass extinctions were associated with ocean acidification, geoengineering an ocean with lower acid levels is obviously beneficial. “A caveat is that we don’t know what the environmental side effects of this would be,” Kruger said, echoing the refrain I’d already heard from Driscoll and others.

  Kruger’s idea depends on something that the algae plan does as well. It’s called ocean subduction, and it refers to the slow movement of chemicals between the upper and lower layers of the ocean. Near the ocean surface, oxygen and atmospheric particles are constantly mixing with the water. When this layer becomes saturated with carbon, we see carbon levels rise in the atmosphere because the ocean can no longer act as a carbon sink. But the lower reaches of the ocean can sequester massive amounts of carbon beyond the reach of our atmosphere. “If the ocean were well mixed overall we wouldn’t have the problem with climate change,” he said. “But the interaction between the deep ocean and the surface is on a very slow cycle.” The goal for a lot of geoengineers is to figure out how to sink atmospheric carbon deep down into the water, where a lot of it will eventually become sediment. Kruger’s limestone plan wouldn’t deliver the carbon directly to the depths, the way the algae plan might have. Instead, the lime would keep more carbon locked into the upper layers of the ocean, allowing time for the ocean’s subduction cycle to carry more of it down into the deep.

  Another possible method of pulling carbon down with rocks is called “enhanced weathering.” In chapter two, we saw how intense weathering from wind and rain on the planet during the Ordovician period actually wore the Appalachian Mountains down to a flat plain. Runoff from the shrinking mountains took tons of carbon out of the air, raising oxygen levels and sending the planet from greenhouse to deadly icehouse. The Cambridge physicist David MacKay recommends this form of geoengineering in his book Sustainable Energy—Without the Hot Air. “Here is an interesting idea: pulverize rocks that are capable of absorbing CO2, and leave them in the open air,” he writes. “This idea can be pitched as the acceleration of a natural geological process.” Essentially, we’d be reenacting the erosion of the Ordovician Appalachians. MacKay imagines finding a mine full of magnesium silicate, a white, frangible mineral often used in talcum powder. We’d spread magnesium silicate dust across a large area of landscape or perhaps over the ocean. Then the magnesium silicate would quickly absorb carbon dioxide, converting it to carbonates that would sink deep into the ocean as sediment.

  However we do it, enhanced weathering relies on the idea that we could take advantage of the planet’s natural geological processes to maintain the climate at a temperature that’s ideal for human survival. Instead of allowing the planet’s carbon cycle to control us, we would control it. We would adapt the planet to our needs by using methods learned from the Earth’s history of extraordinary climate changes and geological transformations. Of course, this all depends on whether we can actually make geoengineering work.

  This diagram illustrates how a number of geoengineering projects could be used to transform the Earth’s climate by drawing carbon out of the atmosphere and reflecting sunlight back into space. (illustration credit ill.17)

  The Moral Hazard

  There is what Kruger and his colleagues call a “moral hazard” in doing geoengineering research, because it could popularize the idea that geoengineering solutions are a magical fix for our climate troubles. If policy-makers believe that there’s a “cure” for climate change just around the corner, they may not try to cut emissions and invest in sustainable energy. “It’s as if a scientist had some good results while testing a cancer cure in mice, and we started telling kids, ‘Hey, it’s OK to smoke, we’re about to cure cancer,’ ” Kruger said. The point is that we’re very far from being certain that geoengineering would work, and until we’ve got a lot more hard data, we have to assume that the best way to slow down climate change is to stop using fossil fuels.

  There’s another worry, too. “There’s a potential for nation-states to see geoengineering activities as a threat,” Cascio cautioned. Harking back to what Driscoll said about how stratospheric reflective particles might cause cooling in some places, but warming in others, Cascio warned that solar management might cause famines in some regions of the world while others cool down into fruitful growing seasons. So one country’s climate solution might be another one’s downfall. A failed experiment in stratospheric particle injection might not just be horrible weather—it might be nuclear retaliation from countries who feel attacked.

  To deal with these moral and political hazards, Kruger and several colleagues created the Oxford Principles, a set of simple guidelines for geoengineers to follow in the years ahead. Spurred by a call from the U.K. House of Commons Science and Technology Committee, Kruger met with a team of anthropologists, ethicists, legal experts, and scientists to draft what he called “general principles in the conduct of geoengineering research.” The Oxford Principles call for:

  1. Geoengineering to be regulated as a public good.

  2. Public participation in geoengineering decision-making.

  3. Disclosure of geoengineering research and open publication of results.

  4. Independent assessment of impacts.

  5. Governance before deployment.

  Kruger emphasized that the principles must be simple for now, because geoengineering is still developing. First and foremost, he and his colleagues want to prevent any one country or company from controlling geoengineering technologies that should be used for the global public good. Principles 2 and 3 touch on the importance of openness in any geoengineering project. (The rogue geoengineer in Canada notably violated principle 2, getting absolutely no input from the public before seeding the waters.) Kruger feels strongly that as long as the public is informed and able to participate, they won’t fear geoengineering in the way many people have come to fear other scientific projects, like GMO crops. Finally, the principles aim to prevent unchecked experimentation that could lead to environmental catastrophe, while also avoiding regulations so restrictive that they stifle innovation. Principle 5, “governance before deployment,” speaks in part to Cascio’s concern about countries interpreting geoengineering as an attack. Before we turn the skies white, or fill the oceans with lime, we must form a governing body that allows nations and their publics to consent to change the fundamental geological processes of the world. “There are huge risks associated with doing this, but doing nothing has huge risks as well,” Kruger concluded.

  To make Earth habitable for another million years, we will have to start taking responsibility for our climate in the same way we now take responsibility for hundreds of thousands of acres of farmland. Geoengineering of som
e kind is critical for our survival, because it’s inevitable that our climate will change over time. Certainly we’ll have to adapt to new climates, but we’ll also want to adapt the climate to serve us and the creatures who share the world’s ecosystems with us. If we want our species to be around for another million years, we have no choice. We must take control of the Earth. We must do it in the most responsible and cautious way possible, but we cannot shy away from the task if we are to survive.

  Of course, we can’t stop at the edges of our atmosphere. If climate change doesn’t extinguish us, an incoming asteroid or comet could. That’s why we’re going to have to control the volume of space around our planet, too. We’ll find out how that would work in the next chapter.

  20. NOT IN OUR PLANETARY BACKYARD

  WE ALREADY KNOW what an asteroid strike did to the creatures who lived during the Cretaceous period. Though it may not have been the sole driver of the K-T mass extinction, the 6.2-mile-diameter bolide that landed off the coast of Mexico roughly 65 million years ago devastated the planet, radically altering the Earth’s climate for possibly a decade or more. Among the scientists who study impacts, that one would have been classed as a 10 out of 10 on the Torino scale, a kind of Richter scale used to quantify impact hazards. Such disasters, where the entire planet is affected, are likely to strike once every 100,000 years or so (though not necessarily with the destructiveness of the K-T impact). That means we are long overdue for another one.

  Will we wake up tomorrow to a newscaster telling us that humanity has six months to live, so we’d better make the best of things before an asteroid wipes us out?

  Not likely. Contrary to Hollywood myths, we’d probably see an asteroid like the one that hit during the K-T mass extinction coming many years before it smashed into us. Less than two decades after scientists discovered the role an asteroid played in the planet’s most recent mass extinction, NASA launched an asteroid-spotting program called Spaceguard. The goal of Spaceguard was to discover and track 90 percent of near-Earth objects larger than a kilometer. A near-Earth object, or NEO, refers to asteroids, meteoroids, comets, and other heavenly bodies whose orbits around the sun bring them close to our own orbit. Most NEOs are not dangerous—they’re either so small that our atmosphere would burn them up, or they zip past us millions of kilometers away. That being said, there is a class of NEO called potentially hazardous objects, or PHOs, and these are the ones we have to be worried about. To achieve PHO status, an object has to be larger than 1 km and its likely trajectory must take it closer than 7,402,982.4 km from Earth.

  That sounds pretty far away, especially when you consider that we’ve had some near misses over the past two decades when sizable asteroids have come within thousands of kilometers of the planet (some would have caused explosions comparable to a nuclear bomb if they had hit). But our solar system is a constantly shifting set of gravitational fields, and the orbits of small objects shift a lot over time. If an asteroid zooms past Jupiter or another planet on its way to us, gravity from that other body could easily pull the asteroid into a new course, converting it from distant to deadly. That’s why astronomers want to keep a sharp eye on any large rocks or balls of ice that come within a few million kilometers of our orbit.

  The good news is that over the past two decades, we’ve gotten pretty good at spotting and tracking NEOs and PHOs. The bad news is that, at least right now, nobody is quite sure what we’d do in what NASA astronomer and asteroid hunter Amy Mainzer calls one of the most hopeful scenarios. That would be when an astronomer—possibly Mainzer herself—verifies tomorrow that there’s a mile-diameter asteroid twenty years out, on a direct collision course with Earth.

  Preparing for an Asteroid Hit

  Mainzer is obsessed with seeing into space. That’s why she’s worked on instrumentation for NASA spacecraft like the WISE (Wide-field Infrared Survey Explorer) satellite, whose sole job was to map as much of the sky as possible using an infrared telescope. Once the WISE mission was complete, Mainzer and her colleagues were able to reprogram the craft in 2010 to scan the sky for NEOs—they dubbed this mission NEOWISE. It was the NEOWISE mission that helped complete the Spaceguard project by identifying enough one-kilometer-or-bigger NEOs that we can say with confidence that we now know where 90 percent of them are. In all, we’ve located nearly 900 NEOs of that size. “That’s good for Earthlings,” Mainzer told me lightly by phone from her office at the Jet Propulsion Lab in California. But then, more seriously, she added, “We don’t know where most of the other ones are.” In her most recent work, Mainzer gathered data on PHOs among asteroids, and she and her colleagues estimate there might be as many as 4,700 of these potential impactors that are bigger than 100 meters. To give you a sense of what that means, a 100-meter asteroid wouldn’t cause a mass extinction, but it would easily flatten a city or a small country. If it landed in the ocean, the tsunamis it generated could do profound damage to coastal areas.

  Given that our local volume of space is swarming with deadly rocks, why aren’t we bombarded all the time? The simple answer is that we are. Every day, we are hit by tiny NEOs, most of which we never notice because they flame out before reaching the Earth’s surface. “You know the video game Asteroids?” Mainzer asks. Of course I do. “Well, it’s actually pretty accurate. Asteroids break up and make more little pieces. And there are far more little pieces than big pieces.” Aside from the relative rarity of larger asteroids, there’s also the fact that our solar system is a dynamic, constantly shifting sea of debris. All the overlapping gravitational fields of the planets and their moons may send rocks spinning into our path, but they also send them spinning out of it, too. “If you put a particle in near-Earth space, it doesn’t stay stable,” Mainzer explained. “After about ten million years, it will go into the outer solar system, crash into the sun, or crash into the Earth.” Keep in mind that 10 million years is nothing to a planet like Earth, which has been around for 4.5 billion years. Essentially, there’s only a short time window for these NEOs to do any damage before they’re hurled elsewhere by gravity.

  Still, Mainzer notes, there are probably “source regions” of the asteroid belt that are constantly resupplying the inner system with new NEOs. Possibly these source regions are shooting out new NEOs because of gravitational resonances with Mars and Jupiter, the two planets whose orbits sandwich the asteroid belt. “I like to think of it as a flipper on a pinball machine,” Mainzer said. “That’s what these resonances are like in the main belt—if an asteroid drops into one, it can get hurled very far from its original location.”

  With the amount of data we’ve gathered from satellites like NEOWISE, it’s reasonable to hope we’d have twenty years to deal with an asteroid or other PHO big enough to cause destruction over the entire Earth. Knowing where most of the large NEOs are can help astronomers to track their movements and determine whether they’re on a collision course. That said, collision courses are always expressed in probabilities. We can’t predict precisely where gravity will tug one of these objects on its way to our cosmic neighborhood. Also, we’re still struggling to track objects that could cause tremendous damage without actually destroying humanity. “Your warning time depends on the design of your instruments,” Mainzer said. She’s currently working on plans for a new space telescope, dubbed NEOCam, designed to spot objects smaller than 100 meters and to find more of those PHOs. “We’re designing it to give us decades of warning,” she said. The goal for Mainzer and others in her field is to get 20 to 30 years of warning for a likely impact, so that we have as many options as possible for stopping it.

  Defending the Planet

  Most people who are serious about defending Earth from PHOs don’t talk about blowing things up. As Mainzer explained with the 8-bit game Asteroids, the problem is that asteroids tend to break down into smaller asteroids. Nuking an incoming object might not do much more than shower our planet with dozens of burning chunks rather than one big one. The damage would be roughly the same. The reason Mainzer
’s data-gathering is so crucial is that the further away an asteroid is when we spot it, the easier it will be to nudge it out of the way. That’s right—our best bet is to nudge it. “Blowing up asteroids may be fun, but an Aikido move would be better,” Mainzer said, only half joking. “Having time gives you the ability to move its trajectory without a lot of energy.”

  The question of how to finesse this Aikido move in space has been the longtime concern of a loose coalition of scientists, policy-makers, and government representatives associated with the Center for Orbital and Reentry Debris Studies. Run by aerospace engineer William Ailor, the Center has developed a series of suggestions over the past 15 years for how we’d deal with asteroid threats. An affable man with tidy gray hair and a touch of the South in his speech, Ailor sketched out how he thought an impact scenario might unfold. “Anyone can find these things,” he said. “There are amateur astronomers all over, as well as more formal programs in space agencies. Most likely, it would be spotted by that community.” If it’s a smaller object, we might have very little time to prepare. “People like to think we’ll have twenty years, but we might only have a few years.”