After Geoengineering

by Holly Jean Buck

  Australia’s Great Barrier Reef, actually a 2,300-kilometer system made up of nearly 3,000 separate reefs, has suffered severe bleaching in the past few years. Daniel Harrison, an Australian oceanographer, is looking at what might be done to buy more time for the Great Barrier Reef. “When the reefs got bleached back to back so badly, two years in a row, we kind of just formed a little informal working group, and were like, ‘You know, if we can send people to the moon, and to Mars maybe soon, then surely we can stop the reef from bleaching, you know? From just overheating.’” The situation is getting dire. “There might be as little as 25 percent of coral cover left from pre-anthropogenic times,” he tells me. “We don’t really know, because nobody started surveying before 1985 … It’s incredible, isn’t it? I mean, you’ve got less than 1 percent of the ocean in coral reefs, and 25 percent all marine life. And it’s not just the Great Barrier Reef that’s in dire trouble, obviously. You know, we’re looking at losing all of that really quite quickly, in evolutionary terms. Quite quickly, in human lifetime terms.”

  The Australian working group formed teams to look at different ideas that could help the reef stay alive. Their investigations showed that most of their exploratory, out-of-the-box ideas wouldn’t scale too well. For example, they wondered: Since the ocean is full of cooler water at deeper depths, could we just pump up some of that in order to cool of the reef? Harrison explains: “You might be able to do something to protect small areas of the reef. Or to maybe protect important coral larvae source reef, and that sort of thing. But none of the other ideas—I mean, it’s just infeasible to move up enough cool water to kind of cool the whole reef.” After considering different options, the researchers honed in on the idea of marine cloud brightening—a form of solar geoengineering—as something worthy of further study. Brighter, more reflective clouds could cool the area. If small salt particles were sprayed into the air, tiny water droplets could condense around them, and these micro-droplets would make the clouds brighter. Harrison is doing modeling research to better understand the feasibility of this idea. The first stage of the modeling his team has done indicates that it might be possible to cool the water by 0.5° to 1°C.

  Another research effort, the Marine Cloud Brightening Project, thinks that this could be a scalable approach with some promise for reefs. I talked with Kelly Wanser, the executive director of the non-profit organization SilverLining and senior advisor to the MCBP, which is led by atmospheric scientist Robert Wood and colleagues at the University of Washington. Wanser describes even more ways scientists are thinking of sustaining corals: they could be genetically modified, or otherwise bred to withstand warmer waters. Robust corals could also be moved into new areas and replanted. But doing these on ecosystem-wide scales would entail a tremendous undertaking just to restore tiny parts of the whole. “The Great Barrier Reef, that’s like reinforcing the Rocky Mountains. It’s massive.”

  “Essentially, it’s heat stress that’s killing corals,” explains Wanser. “They’re affected by other stressors. Heat compounds the other stressors. Heat makes acidity worse. It’s a compound stressor. Heat is the mother of all stressors on corals, and it’s just like there’s a certain delta, and they start to go.” She recalls a recent Ocean Studies Board meeting, where a scientist offered a grim prognosis: there’s maybe twenty years left for 95 percent of the world’s corals. Year by year, the maps went red. “If I didn’t work on solar geoengineering, I would have had to leave, because it was very emotional because to see that. It’s stunning.”

  What would brightening marine clouds actually look like? Essentially, it consists of engineering devices to spray seawater. “There’s certainly some technical challenges to be overcome, but the basic process of just taking sea water and filtering it and then spraying it out, at submicron size, is not that difficult a technical challenge,” Harrison says. His modeling results suggest that there would probably need to be some stations far offshore, beyond the edge of the continental shelf, which would require floating platforms or ships. This gets pricey. The maintenance costs would probably be the larger part, and the whole project could cost around $300 million. Expensive, but then again, the reef brings in an estimated $6 billion to the Australian economy. In Harrison’s conception, you wouldn’t want to brighten the clouds all the time, or even every summer. Rather, it would be done when the coral was at risk of bleaching, which would require about two weeks of forewarning in order to cool the water down to the maximum extent.

  “But, I mean, there’s some real unknowns here, right?” Harrison says. “Because no one’s ever done any field work on this. So, it’s quite unknown. You know, there’s a general belief here that you can only target low-lying marine stratocumulus clouds, if they’re already occurring. But then there’s also quite a large body of evidence that shows that production on the reef influences the local climate, and influences cloudiness in an actual analog to what we’re sort of thinking about.” Essentially, coral can produce a chemical that makes clouds form—though this research on how reefs modify their own climate is in its early stages. His research team is interested, and worried, about how that will change as the reef bleaches, and whether there might be a positive feedback loop, wherein less clouds mean even more bleaching. “So, to some degree, we might be putting the system back towards where it was with aerosol production on the reef. But we really don’t know, so I don’t want to over emphasize that. And it’s probably impossible for us to know, because we started monitoring the reef too late in human history.”

  Indeed, marine cloud brightening comes with a lot of unknowns—in part because cloud–aerosol interactions are not well understood in climate science, more generally. For a big-picture look at what climate models can and can’t tell us, I spoke with Ben Kravitz, an atmospheric science professor at Indiana University who coordinates a project that compares geoengineering model simulations. He explains: “The climate system is inordinately complex. It’s one of the more complicated systems that we know how to deal with. A great example of this is clouds. If you look out the window on an airplane, you can see clouds with all sorts of different structures. They’re moving, some of them are a couple meters across, some of them are tens of kilometers across. Some of them are organized, some of them are not. Basically, you can’t model all of that behavior in any single model, because we don’t have the computational power. If there were a way to understand how clouds behave, in such a way that we could parameterize those behaviors and put them in models that we could actually run, that would solve some of the largest uncertainties in climate science.”

  Newer climate models are better at controlling for clouds’ varying sensitivities to aerosols, so perhaps there will soon be better tools to get information about the effectiveness of marine cloud brightening. But for that to happen, there has to be funding. Kelly Wanser of the Marine Cloud Brightening Project says that applied cloud-brightening research could actually help us understand some of these basic unknowns. However, potential funding organizations may see controlled outdoor field experiments into cloud–aerosol interactions as geoengineering related, because they have geoengineering applications. For the US-based project, their next step is to actually test the nozzle with seawater, which they would like to do on the California coast. The association with geoengineering has made it difficult to raise funding to actually build and test these nozzles. “I think we talked to all of the relevant government agencies who could support this, and essentially there’s no one willing to say, ‘We’ll just do it as the cloud–aerosol basic science.’ They’re like, ‘No, the cat’s out of the bag, this is geoengineering. We would have to get approval.’” So, on one hand, there’s a potential technique that could have global applications, as well as regional or local ones for particular marine ecosystems—but we don’t know how well it would work, or what it would take to do it. On the other hand, it’s been difficult to fund the research needed to get those answers because of the stigma of geoengineering.

  Another asp
ect of marine cloud brightening that lies at the edges of scientific understanding is the teleconnections in the system—for example, how clouds in one place are connected to weather in another place. Anthony Jones, a climate modeler, has simulated regional solar geoengineering using stratospheric aerosols. His work has examined what happens when only certain parts of the system are modified. He tells me, “I think it scares me, the thought of doing marine cloud brightening.” Because of all these weird teleconnections that we don’t understand, I ask? “Yeah, the teleconnections. I’ve been looking at that a bit in some of our [stratospheric aerosol] simulations recently. So if you cool the North Pacific, you can actually shift the position of the jet stream … You get cold temperature on the western half of America, and warmer temperature on the eastern half of America,” Jones explains. “The teleconnections are almost unavoidable, and if you can cool a certain area significantly, you are going to change the climate and the weather response.” For this reason, Daniel Harrison thinks any attempt to use marine cloud brightening on a global scale would bring up major questions around governance: “If you want to cool the whole planet by doing marine cloud brightening, you know, some places are going to cool more than others. You’re certainly going to alter, to some degree, global weather patterns. Maybe not that much, in the scheme of things, but it might not have to be very much to disadvantage some group of people living in some certain place, while advantaging everybody on the average.” On the other hand, the concern about shifting weather patterns in remote places is less severe when it comes to brightening marine clouds over a reef, versus trying to modify temperatures globally with this technique. Those are two different goals. It would be better to consider something like area-specific marine cloud brightening for reefs to be a form of radical adaptation, rather than geoengineering.

  So who cares about coral reefs, besides enamored children watching movies about clownfish? Coral reefs are not just a backdrop for colorful fish and exotic species. Reefs protect coasts from storms; without them, waves reaching some Pacific islands would be twice as tall. Over 500 million people depend on reef ecosystems for food and livelihoods.1 Therefore, keeping these ecosystems functioning is a climate justice issue. Again, over 99 percent of corals would be wiped out at a two-degree-Celsius temperature rise, and perhaps 70 to 90 percent would be lost at 1.5 degrees.2 And even if temperatures eventually stabilize at 1.5 degrees of warming a century or two from now, it’s not known how well coral reef ecosystems would survive a temporary overshoot to higher temperatures.

  Are we basically agreeing to give up on coral, and all the other animals and plants and unique forms of life in reefs, and the human economies and communities they support? On a societal level, it seems so. Many coral scientists, however, aren’t willing to give up, though they oscillate between hope and despair, as ethnographer Irus Braverman finds in her research. In her book Coral Whisperers, Braverman describes how this polarity maps on to the rift between those conservation scientists who believe that it is possible to use traditional conservation methods (like withdrawal of human impacts), and others who take a more interventionist approach (on the basis that the natural systems are already fundamentally altered). Interestingly, she notes that “female scientists, many of them young and with diverse backgrounds, have taken the lead in promoting narratives of hope and models for assisted evolution.”3 But the restoration efforts in which many coral scientists are engaged stop short of intervention in the climate; some scientists in Braverman’s book describe these efforts as holding together a patchy safety net, or as reef gardening—according tiny spaces of management that would hopefully survive an overshoot, like an outdoor aquarium in which to keep them until global warming is managed.

  Is the survival of these life-forms and lifeways important enough to warrant research and discussion of geoengineering, or to justify coming up with a different conceptual category and language around geoengineering that would include more targeted interventions? It seems not. Nonhuman life is relatively absent from the anthropocentric geoengineering discussion, even though, as the saying goes, extinction is forever.

  “The corals are a little bit like the canary in the gold mine,” Harrison says. “They’re very, very temperature sensitive. I really do think it’s just a harbinger of things to come. You know, the coral ecosystem might collapse first, but I think there might be quite a few more ecosystems that’ll follow it. I think that life is very resilient, but ecosystems as we know them aren’t.” Other ecosystems are also at high risk from even small changes in global mean temperature: Arctic ecosystems, mountain glaciers, and the Redwood forests in California, for instance. So are species that can’t move quickly and find another suitable ecosystem. “It’s the things that already live at the kind of extreme ends of the scale, and that can’t move, right? So coral reefs, you know, they’re stuck in already some of the warmest waters. If it gets too hot for them there, then (a) they can’t move, and (b), they’ve got nowhere to go anyway. And the same with the extremely cold ecosystems. And the same with the Redwood forests. I guess. Trees can’t up and move quickly enough to keep up with climate change.”

  Once you delve into the temporalities of the climate change problem—and especially the permanence of some of these changes, like extinction—it’s easy to see how the idea of solar geoengineering makes its entrance. You’re not reading this book in 1990, when carbon dioxide concentrations were still in the neighborhood of 350 parts per million. At this point, most people would agree that there’s at least a chance we don’t decarbonize before we lock in dangerous change—and for sensitive species and ecosystems like coral, the danger threshold has already been passed. The question, then, emerges: Can one use solar geoengineering to keep ecosystems on life support and forestall climate tipping points, while also decarbonizing?

  Enter the “peak shaving” scenario, which uses solar geoengineering to “shave the peak” off of warming while carbon dioxide levels are being brought down. While we’ve discussed marine cloud brightening above, “solar geoengineering” in this context usually implies stratospheric aerosol injection, which would be a global- scale program.

  In a nutshell, the most basic version of this peak-shaving scenario (depicted in Figure 2) means using specially designed high-altitude aircraft—perhaps a small airline’s worth—to constantly fly aerosol precursors into the stratosphere. These aerosol precursors would cause the formation of particles made from sulfur, calcite, or some yet-to-be-determined substance. Why, if the world is trying to reduce particulate air pollution, would we put more particles up there? The particles are injected into the stratosphere—a layer of the atmosphere above where clouds form, and higher than planes usually fly. This means they would not fall back to earth in only a few days, as pollution from trucks and factories tends to. Rather, they would circulate around the whole planet, staying aloft for a year or so. Nevertheless, such an undertaking would not be without human health impacts. One study estimated an additional 26,000 deaths per year with enough sulfur-based geoengineering to offset one degree Celsius of warming, due to air quality and ultraviolet exposure; for comparison, 4 million people currently die each year from degraded air quality.4 Indeed, the idea is to create a blanket of intentional, high-altitude pollution that would reflect something like 1 to 2 percent of incoming sunlight, perhaps less. Depending on one’s perspective, this may sound mundane, or it may sound like an alarmingly unprecedented intervention into a poorly understood system.

  Figure 2. Conceptual diagram of using solar geoengineering to “shave the peak” off a temperature overshoot. Sometimes called the “napkin diagram,” based on a presentation by John Shepherd at Asilomar in 2010. Version source: Doug MacMartin

  We’ve come full circle, then, since the beginning of this book. Is “buying time” for carbon removal a legitimate reason for doing a limited amount of solar geoengineering? Or is it a weak justification for a project that will send the earth system careening down a dangerous road? Once started, how wo
uld people make sure the carbon really does get removed? In this chapter, we will look at some best-case and worst-case scenarios for a climate intervention program that includes solar geoengineering.

  Kingston, Jamaica, July, 92°F / 33°C

  Rain clouds hang in the Blue Mountains but never descend. The sidewalks in Kingston are jammed with people in business suits walking to work and street vendors selling sweets, making their way through fumes and honking and reggae blaring from car stereos. It is a glorious morning. I catch a ride up to the university, where there’s a meeting about solar geoengineering research governance—the first such convening here in Jamaica.

  The country has recently suffered from a drought, and while people here are accustomed to dry periods, yearlong droughts are something new. “Unfamiliarity is transforming our sensitivity into a vulnerability,” explains the first speaker, climate scientist Michael Taylor. Jamaica has steep slopes and narrow coastal plains; with limited water storage, farms are largely dependent on rainfall. Livelihood, well-being, and water access here and elsewhere in the Caribbean are linked to the rains. But now the rain is more variable; the “nature” of rain is changing. Nighttime temperatures are soaring; one has to run the fan straight through the night. The climate will keep changing, Taylor says, with 98 percent of days here being “hot” by the 2090s—he emphasizes that only 2 percent of them will be cool.

  It’s sweltering in this room, and we’re shifting uncomfortably on our wooden seats. There are a few fans, an adaptation to the broken AC, but even the local residents are sweating beads. Someone makes the inevitable joke about our prospects for controlling the global climate when we can’t even control the climate in the room—a joke that’s been made at approximately one-third of the geoengineering meetings I’ve ever been at. We press on.