Dimming the Sun to Cool the Planet Is a Desperate Idea, Yet We’re Inching Toward It | Bill McKibben | The New Yorker

If we decide to “solar geoengineer” the Earth—to spray highly reflective particles of a material, such as sulfur, into the stratosphere in order to deflect sunlight and so cool the planet—it will be the second most expansive project that humans have ever undertaken. (The first, obviously, is the ongoing emission of carbon and other heat-trapping gases into the atmosphere.) The idea behind solar geoengineering is essentially to mimic what happens when volcanoes push particles into the atmosphere; a large eruption, such as that of Mt. Pinatubo, in the Philippines, in 1992, can measurably cool the world for a year or two. This scheme, not surprisingly, has few public advocates, and even among those who want to see it studied the inference has been that it would not actually be implemented for decades. “I’m not saying they’ll do it tomorrow,” Dan Schrag, the director of the Harvard University Center for the Environment, who serves on the advisory board of a geoengineering-research project based at the university, told my colleague Elizabeth Kolbert for “Under a White Sky,” her excellent book on technical efforts to repair environmental damage, published last year. “I feel like we might have thirty years,” he said. It’s a number he repeated to me when we met in Cambridge this summer.

Others, around the world, however, are working to speed up that timeline. There are at least three initiatives under way that are studying the potential implementation of solar-radiation management, or S.R.M., as it is sometimes called: a commission under the auspices of the Paris Peace Forum, composed of fifteen current and former global leaders and some environmental and governance experts, that is exploring “policy options” to combat climate change and how these policies might be monitored; a Carnegie Council initiative of how the United Nations might govern geoengineering; and Degrees Initiative, an academic effort based in the United Kingdom and funded by a collection of foundations, that in turn funds research on the effects of such a scheme across the developing world. The result of these initiatives, if not the goal, may be to normalize the idea of geoengineering. It is being taken seriously because of something else that’s speeding up: the horrors that come with an overheating world and now regularly threaten its most densely populated places.

This year, the South Asian subcontinent went through an unprecedented spring heat wave, and then the heat settled, for nearly the entire summer, on China. Drought plagued Europe, while Pakistan endured the worst floods in decades, and the Horn of Africa suffered a fifth consecutive failed rainy season. All this, along with more systemic damage, such as the melt at the poles, happened with a globally averaged temperature increase of just slightly more than one degree Celsius over pre-Industrial Revolution temperatures. To the extent that nations have agreed on anything about climate change, it’s that we need to limit that temperature rise; with the 2016 Paris climate accords, nations adopted a resolution that committed them to “holding the increase in the global average temperature to well below 2° C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5° C above pre-industrial levels.”

The method to accomplish this was supposed to be the reduction of emissions of carbon dioxide and methane by replacing fossil fuels with clean energy. That is happening—indeed, the pace of that transition is quickening perceptibly in the United States, with the adoption of the Biden Administration’s Inflation Reduction Act and its ambitious spending on renewable power. But it’s not happening fast enough: the Intergovernmental Panel on Climate Change has said that we need to cut worldwide emissions in half by 2030, and we’re not on track to come particularly close to that target—in this country or globally. Even before 2030, we may, at least temporarily, pass the 1.5-degree mark. In late September, the longtime NASA scientist James Hansen, who has served as the Paul Revere of global warming, pointed out on his Web site that 2022, like most years in recent decades, will be one of the hottest on record, which is remarkable in this case, because the Pacific is in the grips of a strong La Niña cooling cycle. And the odds are strong, Hansen wrote, that there will be a hot El Niño cycle sometime next year, which means that “2024 is likely to be off the chart as the warmest year on record . . . Even a little futz of an El Nino — like the tropical warming in 2018-19, which barely qualified as an El Nino — should be sufficient for record global temperature. A classical, strong El Nino in 2023-24 could push global temperature to about +1.5°C.”

It’s likely, in other words, that conditions may force a reckoning with the idea of solar geoengineering—of blocking from the Earth some of the sunlight that has always nurtured it. Andy Parker is a British climate researcher who has worked on geoengineering for more than a decade—first at the Royal Society and then at Harvard’s Kennedy School—and now runs the Degrees Initiative. He told me, “For the whole time I’ve worked on this, it’s been like nuclear fusion—always a few decades away no matter when you ask. But there are going to be events in the next decade or so that will sharpen people’s minds. When temperatures approach and then cross 1.5 centigrade, that will be a non-arbitrary moment.” He added, “That’s the first globally agreed climate target we’re on course to break. Unless we find a way to remove carbon in quantities not imaginable presently, this would be the only way to stop or reverse rapidly rising temperature.”

Everyone studying solar geoengineering seems to agree that it’s a terrible thing. “The idea is outlandish,” Parker told me. Mohammed Mofizur Rahman, a Bangladeshi scientist who is one of Degrees Initiatives’ grantees, noted, “It’s crazy stuff.” So did the veteran Hungarian diplomat Janos Pasztor, who runs the Carnegie initiative on geoengineering governance, and said, “People should be suspicious.” Pascal Lamy, a former head of the World Trade Organization (W.T.O.), who is the president of the Paris Peace Forum, agreed, saying, “It would represent a failure.” Jesse Reynolds, a longtime advocate of geoengineering research, who launched the forum’s commission, wrote recently that geoengineering’s “reluctant ‘supporters’ are despondent environmentalists who are concerned about climate change and believe that abatement of greenhouse gas emissions might not be enough.” Reynolds speaks for this geoengineering community on this point. They are, to a person, willing to acknowledge that reducing emissions by replacing coal, gas, and oil represents a much better solution. “I think the basic answer is moving more rapidly out of fossil fuels,” Lamy said. “I’m a European. I’ve been supporting this view for a very long time. Europe is in some ways well ahead of others.”

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