A new study on global warming confirms what many have believed for years: that the thinning snowpack in the Rockies is a result of global warming. While this year was out of the ordinary, with heavy snowfall throughout the winter season (which has in turn caused lots of spring flooding), overall, the snowfall levels are trending downward.
This isn’t just bad news for winter sports enthusiasts. According to Greg Pederson of the U.S. Geological Survey in Bozeman, Montana, over 70 million people rely on the water from snow melting in the Rockies. That water feeds the Columbia, Missouri, upper Colorado rivers, and even the Rio Grande.
So how did researchers come to this conclusion? People weren’t measuring the snow levels even 100 years ago, let alone 500 or 1000 years back in history. Luckily, nature takes it’s own record of snow levels, storing it in tree rings. Pederson and his colleagues looked at tree rings through two lenses:
- Trees have fat rings during wet years, which signals higher snowpack, and skinny rings during a dry season, with less snow.
- The growth of trees at higher elevations is stunted because of higher snow levels (they don’t begin to grow until the snow melts in the spring).
Using these two factors, they were able to look back hundreds of years, putting the data into a larger historical context. Pederson says, “The 20th century, across the northern Rockies, looks quite low, on average, compared to the amount of snow that was there over the past millennium.” He attributes this diminished snow levels to the global warming trend, with the data they collected showing the affects that warming temperatures have on the snow levels. “After we get the delivery of snow, we’re oftentimes seeing warmer air masses coming in afterward. So even if it’s dropped as snow, everything’s warmer, so it tends to melt faster once the snow is delivered.”
How does this impact the future of the Rockies? Farmers will need to prepare for the potential longer, drier, and warmer summers if snow levels cannot provide the area with a steady supply of water. While this may be many years, even decades away, learning to conserve resources now will help in the long run. It’s hard to hear about the possibility of long-term droughts when there has been widespread flooding this year across the country, but one of the main focuses of Pederson’s research was that you can’t judge climate change by a single year, decade, or a few decades. You have to go back several centuries to see the overall trend.
Results from Pederson’s study will be featured in this month’s issue of Science magazine. Read more about Pederson’s research on NPR.org.
