From 30,000 ft. in the air, the Greenland ice cap seems impregnable, nearly 800 trillion gal. of frozen water locked safely away. But get closer and the cracks begin to emerge. Dancing by helicopter above the mouth of the Jakobshavn Glacier, near the western coast of Greenland, you can make out veins of the purest blue meltwater running between folds of ice. What you can't see is Jakobshavn's inexorable slide toward the sea at 65 ft. to 115 ft. a day--an alarming rate that has accelerated in recent years. As the glacier nears the coast, it breaks off into the Ilulissat fjord, a stream of churning ice that might have birthed the monster that sunk the Titanic. Those icebergs are spat out into Disko Bay, 20 billion metric tons' worth every year, where they loom above the tiny fishing boats that ply these deep, cold waters. Sail close and you'll find that these seemingly permanent cathedrals of ice, some 200 ft. to 300 ft. high, are leaking water like broken pipes. They're dying.
Greenland is the front line in humanity's battle against climate change. The warming that is easy to dismiss elsewhere is undeniable on this 860,000-sq.-mi. island of fewer than 60,000 people. More and more of Greenland, whose frozen expanses are a living remnant of the last ice age, disappears each year, with as much as 150 billion metric tons of glacier vanishing annually, according to one estimate. If all the ice on Greenland were to melt tomorrow, global sea levels would rise more than 20 ft.--enough to swamp many coastal cities. Though no one thinks that will happen anytime soon, what keeps glaciologists awake at night is that thinking is not the same as knowing--and no one can say with certainty what Greenland's fate will be.
That's why researchers like Dorthe Dahl-Jensen, stationed on a barren speck of land near the heart of Greenland's ice sheet to decode the island's climatic history, is among TIME's heroes for the environment. These scientists, activists, financiers and political and religious leaders--chronicled in the following pages--display a passion for the planet that just might save it.
I got a firsthand look at such heroism this summer when I joined a team of international researchers led by Dahl-Jensen at the NEEM camp in Greenland. NEEM stands for North Greenland Eemian Ice Drilling (the acronym is Danish, as are the leaders of the project), and the scientists are digging deep into the Greenland ice--more than a mile and a half deep to be precise--to try to understand its pedigree. Depth is time, and the lower you go, the further back in history you travel. As ice formed in Greenland, year after cold year, bits of atmosphere were trapped in the layers. Drilling into the ice and fishing out samples--ice cores--that contain tiny bubbles of that ancient air can reveal the temperature, the concentration of greenhouse gases, even the ambient dust from the year that layer was formed. It's like tree rings but for climatic history. "In order to predict the future, we have to understand the past," says Minik Rosing, a geologist at the University of Copenhagen.
NEEM is focused on the Eemian stage, a period from about 115,000 to 130,000 years ago, right before the last ice age, when the world was warm--quite warm, about 9°F hotter in Europe than it is today. Given that the U.N.'s Intergovernmental Panel on Climate Change estimates that temperatures could rise 3.24°F to 7.2°F over the coming century, the Eemian could offer a model for the effect such thermometer swings will have on Greenland's ice. A full climatic record of the Eemian has never been constructed, but over the next several summers (scientific work is seasonal on the freezing-cold island), the NEEM researchers hope to harvest cores that will help them track the state of the ice throughout that era, when Greenland was warm enough to actually be green. Dahl-Jensen believes that with enough information, they will be able to project forward and understand just how vulnerable Greenland is to future melting. "With 10 years of intense research, I think we can reach a reliable estimate for that tipping point," she says.
It's that type of confidence that serves as our light in the climatic darkness, living proof that hope hasn't vanished. You need that comfort when you're standing on a rocky hilltop in Greenland, watching the ice disappear. As Jakobshavn gives way to the fjord, a stadium-size iceberg suddenly implodes, disintegrating like a collapsing skyscraper. I watch as a plume of mist fills the air where the iceberg once was, while the fjord churns on. And then I wonder, Just how much time do Greenland and the rest of us have before it's too late? That may be up to us--and the heroes we choose to follow.
A CNN Worldwide Investigation Planet in Peril To watch more of Anderson Cooper's worldwide investigation Planet in Peril, tune in to AC360° on CNN, Mondays at 10 p.m. E.T., and visit CNN.com/planetinperil Also, don't miss the new documentary Planet in Peril: Battle Lines, Dec. 11 on CNN