I GREW UP in California, where human ingenuity is a force of nature. Computers, the Internet, Hollywood, blue jeans, the Beach Boys - they are all inventions of my home state. The economic and cultural power of these things is obvious. What's less obvious is how they transformed the place that gave birth to them. Until the early 1970s, my hometown of Silicon Valley was mostly orchards and Victorian ranch houses, with rows of cherry and apricot trees that marked the coming of spring with delicate white and pink blossoms. During the PC revolution, I watched those orchards fall to make room for glassy high-tech office buildings. The hillside where I saw the footprint of a mountain lion in the 1970s is now cluttered with houses. Silicon Valley is still a beautiful place, but the blossoms are mostly gone, the sky is hazy, and the beaches are crowded. This is happening everywhere, of course - it's the story of modern life. And there are many upsides to this transformation, including the fact that the ideas and technologies born in California have been a great boon to humanity. But you have to be pretty obtuse to grow up in a place like Silicon Valley and not be aware that progress sometimes comes at a price.
I left the Valley in my midtwenties and moved to New York City to begin a career as a journalist. My connection to the Valley served me well. I spent the next decade or so writing about the business and culture of my hometown for publications such as Rolling Stone and the New York Times Magazine. But my perspective changed after I became the father of three kids. The future of digital culture was suddenly much less interesting to me than the survival of the human race. I spent a lot of time with climate scientists while I was reporting my previous book, which was about the coal industry. It was a sobering experience. I think of myself as an optimistic person, but the deeper you probe into the climate crisis, the darker the story gets. It's hard not to read it as a parable about the dangers of living in a high-tech society. (No matter how hard they tried, a world of hunter-gatherers could not cook the planet.) And it's harder still not to wonder whether the smartest, most technologically sophisticated creatures that ever existed on earth will figure out a solution for this looming catastrophe. My friends in Silicon Valley are sure we can. They believe we are one big idea - Thin film solar! Cellulosic ethanol! High-altitude wind power! - away from solving this crisis. I used to think that, too.
In early 2006, a friend emailed me an essay by Paul Crutzen that was about to be published in an academic journal. Crutzen is a Dutch atmospheric chemist who won the Nobel Prize for his pioneering research on the ozone hole in the atmosphere. In his note, my friend - a successful entrepreneur in the solar power industry - wrote: “Read this. We are in deep trouble. We're going to geoengineer the damn planet now!”
I may have heard the word “geoengineer” once or twice before, but I knew next to nothing about it, other than the fact that it generally referred to people with outlandish ideas about how to counteract global warming. I had a vague memory of reading an article about a handful of scientists - I imagined them toiling in a lab buried deep in a mountain somewhere in New Mexico - who wanted to launch mirrors into space or dump iron into the ocean in a desperate attempt to cool the earth. The title of Crutzen's essay certainly amused me: “Albedo Enhancement by Stratospheric Sulfur Injections: A Contribution to Resolve a Policy Dilemma?” The phrase “albedo enhancement” sounded like a procedure a surgeon might perform on a lonely middle-aged man.
When I started to read, however, I was captivated. The basic facts were familiar: carbon dioxide (CO2) levels in the earth's atmosphere are rising to concentrations not seen in twenty million years, with no end in sight. Meanwhile, the earth's climate is warming even faster than scientists had predicted just a few years ago. What was new in Crutzen's paper - new to me, anyway - was the view that some of this accelerated warming was driven not only by high levels of CO2 but also by the progress we have made in the fight against smog and other traditional pollutants. The tiny particles that cause some kinds of air pollution act like mirrors in the sky, reflecting sunlight away from the earth, which cools the planet. As we eliminate pollution, the particles vanish, letting us all breathe easier - but also letting more sunlight in, which heats up the earth ever faster. As Crutzen pointed out, by trying to save kids from asthma, we were inadvertently making the climate crisis worse.
What to do? Clean air is obviously a good thing: air pollution kills people. The simplest solution would be to cut greenhouse gas emissions. If anyone should have been confident that we could take bold action to address this problem, it should have been Crutzen. After all, he was in part responsible for the fact that the leading nations of the world had come together in the late 1980s to confront another global threat, the ozone hole. In that case, once the risk of ozone damage was clear, action was swift: an international treaty, the Montreal Protocol, was negotiated and signed in 1987, banning ozone-depleting substances. It was an inspiring example of political leaders from around the world coming together to confront a grave threat in a rational and decisive way. But when it came to dealing with greenhouse gases, Crutzen was not so sanguine that a political solution could be found. He understood that the problem of reducing greenhouse gases is far deeper and more complex than eliminating chlorofluorocarbons from refrigerators and air conditioners, in part because greenhouse gas emissions are, in some ways, a proxy for economic health and prosperity. In fact, Crutzen called the notion that industrialized nations would join together and significantly reduce emissions “a pious wish.”
Instead, Crutzen offered a radical proposal: rather than focusing entirely on cutting greenhouse gas emissions, maybe it was time to think about addressing the potentially catastrophic consequences of global warming in a different way. If the problem is too much heat, an obvious solution would be to find a way to reduce that heat. One method to do that would be to increase the earth's reflectivity in ways that would not cause asthma attacks and kill people. As Crutzen knew as well as anyone, about 30 percent of the energy from sunlight that hits the earth is immediately reflected back into space, while the other 70 percent is trapped here by CO2 and other greenhouse gases, warming the planet. If we could reflect just 1 or 2 percent more sunlight away from the earth's surface, it would be like popping up an umbrella on the beach on a hot summer day. Crutzen called it albedo enhancement (“albedo” is just another word for reflectivity).
There are lots of ideas about how one might deflect sunlight away from the planet, from launching mirrors into space to painting roofs white. But as Crutzen pointed out in his paper, the simplest way to do it might be to add a relatively small number of sulfate particles - you can think of them as dust - to the upper atmosphere. The dust would remain in the stratosphere for only a year or so before raining out - so any serious geoengineering scheme would require continuous injection. But unlike pollution in the lower atmosphere, which is where the nasty stuff we breathe resides, pumping a modest amount of particles into the upper atmosphere would pose little danger to human health. The effect they might have on the chemistry of the stratosphere, especially the ozone layer that protects the earth from the sun's ultraviolet light, was, Crutzen admitted, unclea...