Guides get to climb to the summit of Mount Hood every week, he says, so glacier tours are more fun for them.

We climb inside a Sno-Cat and chug up the permafrost of the Palmer ski run, the treads easily navigating the crunchy snow. Halfway up the trail, we encounter Bowker and some of the folks from yesterday's class walking back down the slope with glum expressions. "They turned back," observes Bates. I never find out why.

Weather is often the key factor. My trip here was postponed for two weeks because of snow and rain.

"You could come up," Steve Baldwin, the guide company's co­director, had told me over the phone. "But it would be like being inside a ping-pong ball."

Fortunately, today there are supposed to be clear skies. The Sno-Cat stops at 8,500 feet, the top of the Palmer ski lift, and lets us out. We hike up another 200 feet toward the summit and then put on our crampons, cut across the slope laterally, and step onto the White River Glacier.

I immediately notice the distinct odor of sulfur, which seeps from fumaroles in the main crater above us; the gas stains the rocks yellow. Although the mountain hasn't erupted in a few hundred years, it's still technically a volcano - comforting thought.

I look back at the buildings far below. They look like Monopoly pieces. Over time, the glacier has carved out four moraines of churned-up dirt and rocks, which finger their way down to the tree line. You don't have to be a geologist to realize that the ice mass we're standing on was once two-thirds larger.

"The old-timers around here will tell you it used to go all the way to the lodge," says Bates.

It's difficult to find someone at Mount Hood who doesn't believe in global warming and glacial retreat, because everyone here is on mountains every day, and they see it for themselves.