Last week, at a dinner organized by the New York Times to promote Nathaniel Rich’s magazine-length global-warming history “Losing Earth,” the legendary climate scientist Wallace Smith Broecker — who coined the term “global warming” and is, miraculously, still with us and, at 86, still working — raised his hand and asked to speak. The room had been chattering about the importance of hopefulness in fighting climate change, and in writing about it — a common refrain among advocates battling the possibility of burnout. Broecker wanted to offer a dose of perspective — to cut against the hope a bit, and, he said, give just a sense of how big the problem really is.
There are now devices, he said, capable of extracting carbon out of the atmosphere — that’s the good news. They have about the mechanical complexity of a car, he said, and, at roughly $30,000, cost about as much — that’s the first part of the bad news. To merely match the amount of carbon we are putting into the atmosphere every day, he said, we’d need 100 million of them. To take carbon down by just 3 parts per million (ppm) per year — we are at about 410 ppm right now, and rising, already about 60 ppm above the 350 ppm threshold most scientists believe is the tipping point of problematic change — we’d need 100 million more. To take it down by 20 parts per million, we’d need a billion of the machines, distributed optimally around the planet. Each of them, he reminded the audience, would cost $30,000 — and that was just to build them. Then we’d have to run them.
Of course, Broecker continued, there was another option: solar geoengineering. We could shoot sulfur dioxide into the atmosphere, where it would turn into droplets of sulfuric acid capable of reflecting at least some of the sunlight coming toward Earth — which could counterbalance the planet-warming effects of more greenhouse gases in the atmosphere. It would also be much cheaper. He told me a similar thing when I visited him last year, while researching a long feature surveying worst-case scenarios for climate change. He said then that he doubted he’d live to see the experiment undertaken. “But in your lifetime …”