3:09

“The trend I see is that we’re getting permanent snow pack later, and we get to bare ground sooner. We’ll have years where there was a lot of snow on the ground, and then we lose snow sooner than years that had a lot less snow just because it’s a lot warmer now.”

This is a snow pack that supplies water to most of the southwest.

He's meticulous.

Every day for 40 years, Billy Barr has collected data about snow in the town of Gothic, Colorado, where he lives. He does it just to pass the time, but his data has been invaluable to climate scientists. Researchers at the Gothic-based Rocky Mountain Biological Lab stumbled upon Barr’s data and used it to find clear evidence of climate change.