Rivers fed by melting snow and glaciers supply water to over one-sixth of the world’s population–well over a billion people. But these sources of water are quickly disappearing: the Himalayan glaciers that feed rivers in India, China, and other Asian countries could be gone in 25 years (after this story appeared in print this claim was retracted by scientists: see correction). Such effects of climate change no longer surprise scientists. But the speed at which they’re happening does. “The earth appears to be changing faster than the climate models predicted,” says Daniel Schrag, a professor of earth and planetary sciences at Harvard University, who advises President Obama on climate issues.
Atmospheric levels of carbon dioxide have already climbed to 385 parts per million, well over the 350 parts per million that many scientists say is the upper limit for a relatively stable climate. And despite government-led efforts to limit carbon emissions in many countries, annual emissions from fossil-fuel combustion are going up, not down: over the last two decades, they have increased 41 percent. In the last 10 years, the concentration of carbon dioxide in the atmosphere has increased by nearly two parts per million every year. At this rate, they’ll be twice preindustrial levels by the end of the century. Meanwhile, researchers are growing convinced that the climate might be more sensitive to greenhouse gases at this level than once thought. “The likelihood that we’re going to avoid serious damage seems quite low,” says Schrag. “The best we’re going to do is probably not going to be good enough.”
This shocking realization has caused many influential scientists, including Obama advisors like Schrag, to fundamentally change their thinking about how to respond to climate change. They have begun calling for the government to start funding research into geoengineering–large-scale schemes for rapidly cooling the earth.
Strategies for geoengineering vary widely, from launching trillions of sun shields into space to triggering vast algae blooms in oceans. The one that has gained the most attention in recent years involves injecting millions of tons of sulfur dioxide high into the atmosphere to form microscopic particles that would shade the planet. Many geoengineering proposals date back decades, but until just a few years ago, most climate scientists considered them something between high-tech hubris and science fiction. Indeed, the subject was “forbidden territory,” says Ronald Prinn, a professor of atmospheric sciences at MIT. Not only is it unclear how such engineering feats would be accomplished and whether they would, in fact, moderate the climate, but most scientists worry that they could have disastrous unintended consequences. What’s more, relying on geoengineering to cool the earth, rather than cutting greenhouse-gas emissions, would commit future generations to maintaining these schemes indefinitely. For these reasons, mere discussion of geoengineering was considered a dangerous distraction for policy makersconsidering how to deal with global warming. Prinn says that until a few years ago, he thought its advocates were “off the deep end.”
It’s not just a fringe idea anymore. The United Kingdom’s Royal Society issued a report on geoengineering in September that outlined the research and policy challenges ahead. The National Academies in the United States are working on a similar study. And John Holdren, the director of the White House Office of Science and Technology Policy, broached the idea soon after he was appointed. “Climate change is happening faster than anyone previously predicted,” he said during one talk. “If we get sufficiently desperate, we may try to engage in geoengineering to try to create cooling effects.” To prepare ourselves, he said, we need to understand the possibilities and the possible side effects. Even the U.S. Congress has now taken an interest, holding its first hearings on geoengineering in November.
Geoengineering might be “a terrible idea,” but it might be better than doing nothing, says Schrag. Unlike many past advocates, he doesn’t think it’s an alternative to reducing greenhouse-gas emissions. “It’s not a techno-fix. It’s not a Band-Aid. It’s a tourniquet,” he says. “There are potential side effects, yes. But it may be better than the alternative, which is bleeding to death.”
FIVE GEOENGINEERING SCHEMES
Researchers and entrepreneurs have proposed approaches ranging from the relatively cheap and simple to the elaborate. Here are the ones that have received the most attention so far.
Sulfate Injection: Aircraft, or a hose suspended by hundreds of wing-shaped balloons, could inject aerosols into the upper atmosphere. The particles would reflect light and shade the earth. Pros: It could be cheap and fast-acting, cooling the earth in months. Cons: It could cause droughts. Injections might need to continue for hundreds of years. Photo Credit: Brown Bird Design
The idea of geoengineering has a long history. In the 1830s, James Espy, the first federally funded meteorologist in the United States, wanted to burn large swaths of Appalachian forest every Sunday afternoon, supposing that heat from the fires would induce regular rainstorms. More than a century later, meteorologists and physicists in the United States and the Soviet Union separately considered a range of schemes for changing the climate, often with the goal of warming up northern latitudes to extend growing seasons and clear shipping lanes through the Arctic.
In 1974 a Soviet scientist, Mikhail Budyko, first suggested what is today probably the leading plan for cooling down the earth: injecting gases into the upper reaches of the atmosphere, where