Dust darkens the surface of winter snows, warming it by absorbing sunlight that the white surface would have reflected (difference in albedos). That causes the snow to melt earlier than it otherwise would. According to a new study, overall dust levels in the mountains are about five times greater than they were prior to the mid-19th century, due in large part to increased human activity in the deserts. The study went on to quantify some of the effects dust has on snowmelt in Colorado.
Researchers set up test plots in the San Juan Mountains of Colorado. Some plots were left alone to collect snow and dust naturally, others had extra dust added and a third group had naturally arriving dust removed. It’s pretty easy to guess what happened. On average, according to the study, cleaning away the naturally arriving dust delayed snowmelt by 11 days compared to the plots that were left alone. Adding dust sped up the melt by 7 to 13 days. So there is an average of 18-24 days difference in the time which “clean” snow melts and when dusty snow melts.
What possible effect could this have? Well, due to the long-term established behaviors of plants, those plants are missing the water that results from the snowmelt during the most important phase of their growth: early spring. This is likely another reason why plant growth is starting earlier – the other being warmer temperatures earlier. Unfortunately for the plants, the dust on the snow is causing the snow to melt earlier than warmer temperatures arrive, which helps to trigger spring plant growth. As conditions continue to warm across the southwest U.S. and dust triggers earlier and earlier snowmelt, mountain ecosystems will be forced to respond. That response will have to take place over incredible short time scales, which means quite a few plant species likely won’t survive through the end of this century.
Each new climate-related study that comes out shows that the effects of climate change are happening faster and to a greater degree than even experts recognized just a few short years ago. That might make the job of policy-makers more difficult than it otherwise would be, but it’s the reality we’re all facing. I want to again commend the Congressional Representatives from Colorado that voted to pass H.R. 2454 last week. The threats of climate change obviously made more of an impact than did the threats of the extremist Cons in charge of Colorado’s Republican party. Thankfully, the Congressmembers who fell sway to the Cons’ fear-mongering and lies ended up in the minority. It is of critical importance that our U.S. Senators also recognize the very real threats that climate change poses to all of us and our planet. They need to listen to the majority of Coloradans and Amerians that demand something be done about greenhouse forcing today. The name-calling and polarization the Cons continue to perpetrate aren’t resonating with most of us.