Scientists are investigating whether releasing tons of particulates into the atmosphere might be good for the planet. Not everyone thinks this is a good idea.

By: JON GERTNER

or the past few years, the Harvard professor David Keith has been sketching this vision: Ten Gulfstream jets, outfitted with special engines that allow them to fly safely around the stratosphere at an altitude of 70,000 feet, take off from a runway near the Equator. Their cargo includes thousands of pounds of a chemical compound — liquid sulfur, let’s suppose — that can be sprayed as a gas from the aircraft. It is not a one-time event; the flights take place throughout the year, dispersing a load that amounts to 25,000 tons. If things go right, the gas converts to an aerosol of particles that remain aloft and scatter sunlight for two years. The payoff? A slowing of the earth’s warming — for as long as the Gulfstream flights continue.

Keith argues that such a project, usually known as solar geoengineering, is technologically feasible and — with a back-of-the-envelope cost of under $1 billion annually — ought to be fairly cheap from a cost-benefit perspective, considering the economic damages potentially forestalled: It might do good for a world unable to cut carbon-dioxide emissions enough to prevent further temperature increases later this century.

What surprised me, then, as Keith paced around his Harvard office one morning in early March, was his listing all the reasons humans might not want to hack the environment. “Actually, I’m writing a paper on this right now,” he said. Most of his thoughts were related to the possible dangers of trying to engineer our way out of a climate problem of nearly unimaginable scientific, political and moral complexity. Solar geoengineering might lead to what some economists call “lock-in,” referring to the momentum that a new technology, even one with serious flaws, can assume after it gains a foothold in the market. The qwerty keyboard is one commonly cited example; the internal combustion engine is another. Once we start putting sulfate particles in the atmosphere, he mused, would we really be able to stop?

Another concern, he said, is “just the ethics about messing with nature.” Tall, wiry and kinetic, with thinning hair and a thick beard that gives him the look of the backcountry skier he is, Keith proudly showed me the framed badge that his father, a biologist, wore when he attended the landmark United Nations Conference on the Human Environment in Stockholm in 1972. Now 53, Keith has taken more wilderness trips — hiking, rock climbing, canoeing — than he can properly recall, and for their recent honeymoon, he and his wife were dropped off by helicopter 60 miles from the nearest road in northern British Columbia. “It was quite rainy,” he told me, “and that ended up making it even better.” So the prospect of intentionally changing the climate, he confessed, is not just unpleasant — “it initially struck me as nuts.”

It still strikes him as a moral hazard, to use a term he borrows from economics. A planet cooled by an umbrella of aerosol particles — an umbrella that works by reflecting back into space, say, 1 percent of the sun’s incoming energy — might give societies less incentive to adopt greener technologies and radically cut carbon emissions. That would be disastrous, Keith said. The whole point of geoengineering is not to give us license to forget about the buildup of CO₂. It’s to lessen the ill effects of the buildup and give us time to transition to cleaner energy.

Beyond these conceivable dangers, though, a more fundamental problem lurks: Solar geoengineering simply might not work. It has been a subject
of intense debate among climate scientists for roughly a decade. But most of what we know about its potential effects derives from either computer simulations or studies on volcanic eruptions like that of Mount Pinatubo in 1991, which generated millions of tons of sunlight-scattering particulates and might have cooled the planet by as much as 0.5 degrees Celsius, or nearly 1 degree Fahrenheit. The lack of support for solar geoengineering’s efficacy informs Keith’s thinking about what we should do next. Actively tinkering with our environment — fueling up the Gulfstream jets and trying to cool things down — is not something he intends to try anytime soon, if ever. But conducting research is another matter.

A decade ago, when Keith was among the few American scientists to advocate starting a geoengineering research program, he was often treated at science conferences as an outlier. “People would sort of inch away or, really, tell me I shouldn’t be doing this,” he said. Geoengineering was seen as a scientific taboo and Keith its dark visionary. “The preconception was that I was some kind of Dr. Strangelove figure,” he told me — “which I didn’t like.”

Attitudes appear to have changed over the past few years, at least in part because of the continuing academic debates and computer-modeling
studies. The National Academy of Sciences endorsed the pursuit of solar geoengineering research in 2015, a stance also taken in a later report by the Obama administration. A few influential environmental groups, like the Natural Resources Defense Council and the Environmental Defense Fund, now favor research.

In the meantime, Keith’s own work at Harvard has progressed. This month, he is helping to start Harvard’s Solar Geoengineering Research
Program, a broad endeavor that begins with $7 million in funding and intends to reach $20 million over seven years. One backer is the Hewlett Foundation; another is Bill Gates, whom Keith regularly advises on climate change. Keith is planning to conduct a field experiment early next year by putting particles into the stratosphere over Tucson.

The new Harvard program is not merely intent on getting its concepts out of the lab and into the field, though; a large share of its money will also be directed to physical and social scientists at the university, who will evaluate solar geoengineering’s environmental dangers — and be willing to challenge its ethics and practicality. Keith told me, “It’s really important that we have a big chunk of the research go to groups whose job will be to find all the ways that it won’t work.” In other words, the technology that Keith has long believed could help us ease our predicament — “the nuclear option” for climate, as one opponent described it to me, to be considered only when all else has failed — will finally be investigated to see whether it is a reasonable idea. At the same time, it will be examined under the premise that it may in fact be a very, very bad one.

Climate change already presents a demoralizing array of challenges — melting ice sheets and species extinctions — but the ultimate severity of its impacts depends greatly on how drastically technology and societies can change over the next few decades. The growth of solar and wind power in recent years, along with an apparent decrease in coal use, suggest that the global community will succeed in curtailing CO₂ emissions. Still, that may not happen nearly fast enough to avert some dangerous consequences. As Keith likes to point out, simply reducing emissions doesn’t reverse global warming. In fact, even if annual global CO₂ emissions decrease somewhat, the total atmospheric CO₂ may continue to increase, because the gas is so slow to dissipate. We may still be living with damaging amounts of atmospheric carbon dioxide a half-century from now, with calamitous repercussions. The last time atmospheric CO₂ levels were as elevated as they are today, three million years ago, sea levels were most likely 45 feet higher, and giant camels roamed above the Arctic Circle.

‘No matter what, if we emit CO2, we are hurting future generations.’


Recently, I met with Daniel Schrag, who is the head of the Harvard University Center for the Environment, an interdisciplinary teaching and research department. Schrag, who helped recruit Keith to Harvard, painted a bleak picture of our odds of keeping global temperatures from rising beyond levels considered safe by many climate scientists. When you evaluate the time scales involved in actually switching our energy systems to cleaner fuels, Schrag told me, “the really depressing thing is you start to understand why any of these kinds of projections — for 2030 or 2050 — are absurd.” He went on: “Are they impossible? No. I want to give people hope, too. I’d love to make this happen. And we have made a lot of progress on some things, on solar, on wind. But the reality is we haven’t even started doing the hard stuff.”

Schrag described any kind of geoengineering as “at best an imperfect solution that is operationally extremely challenging.” Yet to Schrag and Keith, the political and technical difficulties associated with a rapid transition to a zero-carbon-emissions world make it sensible to look into geoengineering research. There happens to be a number of different plans for how to actually do it, however — including the fantastical (pumping seawater onto Antarctica to combat sea-level rise) and the impractical (fertilizing oceans with iron to foster the growth of algae, which would absorb more CO₂). Some proposals involve taking carbon out of the air, using either immense plant farms or absorption machines. (Keith is involved with such sequestration technology, which faces significant hurdles in terms of cost and feasibility.) Another possible approach would inject salt crystals into clouds over the ocean to brighten them and cool targeted areas, like the dying Great Barrier Reef. Still, the feeling among Keith and his colleagues is that aerosols sprayed into the atmosphere might be the most economically and technologically viable approach of all — and might yield the most powerful global effect.

It is not a new idea. In 2000, Keith published a long academic paper on the history of weather and climate modification, noting that an Institute of Rainmaking was established in Leningrad in 1932 and that American engineers began a cloud-seeding campaign in Vietnam a few decades later. A report issued in 1965 by President Lyndon B. Johnson’s administration called attention to the dangers of increasing concentrations of CO₂ and, anticipating Keith’s research, speculated that a logical response might be to change the albedo, or reflectivity, of the earth. To Keith’s knowledge, though, there have been only two actual field experiments so far. One, by a Russian scientist in 2009, released aerosols into the lower atmosphere via helicopter and appears to have generated no useful data. “It was a stunt,” Keith says. Another was a modest attempt at cloud brightening a few years ago by a team at the Scripps Institution of Oceanography at the University of California, San Diego.

Downstairs from Keith’s Harvard office, there is a lab cluttered with students fiddling with pipettes and arcane scientific instruments. When I visited in early March, Zhen Dai, a graduate student who works with Keith, was engaged with a tabletop apparatus, a maze of tubes and pumps and sensors, meant to study how chemical compounds interact with the stratosphere. For the moment, Keith’s group is leaning toward beginning its field experiments with ice crystals and calcium carbonate — limestone — that has been milled to particles a half-micron in diameter, or less than 1/100th the width of a human hair. They may eventually try a sulfur compound too. The experiment is called Scopex, which stands for Stratospheric Controlled Perturbation Experiment. An instrument that can disperse an aerosol of particles — say, several ounces of limestone dust — will be housed in a gondola that hangs beneath a balloon that ascends to 70,000 feet. The whole custom-built contraption, whose two small propellers will be steered from the ground, will also include a variety of sensors to collect data on any aerosol plume. Keith’s group will measure the sunlight-scattering properties of the plume and evaluate how its particles interact with atmospheric gases, especially ozone. The resulting data will be used by computer models to try to predict larger-scale effects.

But whether a scientist should be deliberately putting foreign substances into the atmosphere, even for a small experiment like this, is a delicate question. There is also the difficulty of deciding on how big the atmospheric plumes should get. When does an experiment become an actual trial run? Ultimately, how will the scientists know if geoengineering really works without scaling it up all the way?

Keith cites precedents for his thinking: a company that scatters cremation ashes from a high-altitude balloon, and jet engines, whose exhaust contains sulfates. But the crux of the problem that Harvard’s Solar Geoengineering Research Program wrestles with is intentionality. Frank Keutsch, a professor of atmospheric sciences at Harvard who is designing and running the Scopex experiments with Keith, told me: “This effort with David is very different from all my other work, because for those other field experiments, we’ve tried to measure the atmosphere and look at processes that are already there. You’re not actually changing nature.” But in this case, Keutsch agrees, they will be.

Source: https://www.nytimes.com