The name "arctic" comes from ancient Greek meaning "Land of the Great Bear."

But the warming climate is threatening this icon of the arctic, the polar bear. Flying above the sub-arctic region of Hudson Bay, Canadian scientist Nick Lunn is hunting polar bears in a 30-year study that tracks their health. It's the job of his assistant Evan Richardson to take them down with a tranquilizer dart.

Once tranquilized, Lunn carefully checks the bear with a pole, without getting too close.

The polar bear is the largest predator on land. Native people in the region say he'll even hunt humans, but not on the day Pelley joined Lunn: with the tranquilizer, the bear was awake but immobile.

The scientists knew this bear by his tattoo. His history is written chapter and verse in the "bear bible."

"This is the record book of all the bears that have been handled by us or Manitoba Conservation," Lunn explains.

The study began at the Wapusk National Park, because the bear population was thought to be the healthiest in the world.

Lunn's annual checkup records changes in fat, dimensions and an inventory of weapons. The polar bear uses its teeth to hunt primarily one thing — seals. That's where arctic warming comes in.

Polar bears can only hunt on the ice. Lunn says the ice is breaking up three weeks earlier than it did 30 years go. He's now finding female bears 55 pounds lighter — weaker mothers with fewer cubs.

Asked how the bear population has changed since he started his research, Lunn says, "When we first started doing this research, we've done inventories in the mid-80s, in the mid-90s. Both times we came out with an estimate of approximately 1,200 animals for what is known as the western Hudson Bay population. The numbers now suggest that the population has declined to below 1,000."

The bears are unlikely to survive as a species if there's a complete loss of ice in summer, which the arctic study projects will happen by the end of this century.

There are skeptics who question climate change projections like that, saying they're no more reliable than your local weatherman. But Mayewski says arctic projections done decades ago are proving accurate.