It is over 50 degrees, and it’s mid-February here in the winter backcountry of Millcreek Canyon, just east of Salt Lake City. The snowpack is soft and slushy. And it’s melting. Whether this is climate change or not, skiers should be disappointed by this early melt-out. For millions of people living in the Wasatch front valleys below, things might be ok, but only as long as the early snowmelt can still supply enough fresh water.
Some think that warming temperatures are not the whole story here.
“There’s this popular misconception that snow melts faster because of increases in temperature,” says Tom Painter, who spoke at a TED talk last year. “Now, it’s true that that’s the case. But that’s not the primary driver. The primary driver is absorbed solar radiation.”
Painter is a geophysicist at NASA’s Jet Propulsion Laboratory and used to work at the University of Utah. He says the thing forcing snow to melt earlier is not just the temperature, but also darkly colored particles of dust.
“There are little particles in there. Little black carbon particles, dust particles, pollen, that are just slowly absorbing a little bit of radiation, and putting that into the snow.”
When dust gets blown onto the snow’s surface, Painter says it reduces the snow’s albedo, or its ability to reflect back the sun’s radiation, causing it to melt faster. About 10 years ago he and other researchers in Colorado began studying how dust from the four corners area was affecting the alpine snowpack of the San Juan Mountains in western Colorado, a major source of water feeding the Colorado river.