Environment

Wildfires continue to rage across parts of Northern California and Washington, producing images that look familiar to many in Colorado.

First of a five-part series

The history of fire in the American Southwest is buried in a catacomb of rooms under the bleachers of the football stadium at the University of Arizona.

Here rules professor Thomas Swetnam, tree ring expert. You want to read a tree ring? You go to Tom. He's a big, burly guy with a beard and a true love for trees.

Ten years ago, a piece of ice the size of Rhode Island disintegrated and melted in the waters off Antarctica. Two other massive ice shelves along the Antarctic Peninsula had suffered similar fates a few years before. The events became poster children for the effects of global warming. But a new study finds that the story isn't quite so simple.

There's no question that unusually warm air triggered the final demise of these huge chunks of ice. But a lingering question is whether these events can be attributed to human-induced global warming.