“You never want to be a company that succeeds because things are going terribly,” Dan Whaley says of his South Park startup’s apocalypse-ready product. “But here we are.” Whaley’s company, Climos, is peddling an idea that is elegantly simple in its outline, fiendishly complex in its details, and, at least at first blush, batshit crazy: It aims to fight global warming by seeding the ocean with iron.

But ocean iron fertilization, as it’s called, is far from insane. In fact, it’s a promising (albeit controversial) area of study in the emerging field of geoengineering, which attempts to right our climate wrongs not by cutting carbon emissions but by manipulating the earth’s atmosphere. The idea has caught on among scientists who argue that the world isn’t likely to change its carbon-heavy ways anytime soon. “Even if we stopped emitting carbon right now, we’d still have a climate problem,” says Ken Buesseler, senior scientist at Massachusetts’ Woods Hole Ocean­ographic Institution. “We shouldn’t rule out any option.”

Here’s how it works: Our oceans are startlingly good at stripping carbon from our atmosphere—at any given time, around 90 percent of Earth’s CO² molecules lie deep underwater, where they can’t contribute to climate change. Iron is crucial to this process, sweeping in from land to help fertilize microscopic plants that absorb carbon. When those plants die a few weeks later, they take that carbon with them to the ocean floor, where it remains for anywhere between a century and a millennium. Whaley proposes dropping a water-soluble iron-liquid mixture in the deep waters of the Southern Ocean above Antarctica—the optimal location, studies suggest—to increase plant production and the uptake of carbon. Researchers estimate that iron seeding, done right, could absorb more than 10 percent of our carbon emissions each year. As Whaley puts it, “It’s not a silver bullet, but it is part of the solution.”

Iron fertilization occupied a legal gray area for years (you can’t just dump stuff in the water, even for science’s sake), but the international bodies that govern the sea recently agreed to allow more testing. In the next few years, Whaley is hoping to launch an experimental 60-day cruise cov­ering a 93-square-mile area. All he needs is money. While Climos raised $3.5 million last year (investors included Elon Musk, cofounder of electric-car maker Tesla), Whaley figures he’ll need another $15 million for the expedition.

There may be an even bigger hurdle, though: No one is sure that iron fertilization is safe. In fact, many environmental groups believe that iron might harm fisheries and create massive “dead zones” where nothing will grow. But Whaley counters that we must act sooner rather than later to avoid the ravages of climate change, even if we’re not actually sure how our actions will pan out. And that, ultimately, is what geoengineering comes down to. Whaley is betting that if efforts to slash emissions fail and San Francisco starts looking like New Orleans post-Katrina, we’re going to want a Plan B. “More knowledge is better. If we’re going to be stupid, we’ll be stupid anyway, only in worse ways.”