June 10, 2011
Rocky Mountains Losing Their Snow
Trees grow at high elevations in the Rockies, fed by melting snow. (Photo: Greg Pederson, 2009, © Science/AAAS)
More than 70 million people across the North American West depend on water from the Columbia, Missouri or Colorado Rivers. And 60 to 80 percent of that water originates as snowpack. But that snowpack has been declining in recent decades, a worrisome trend as Western cities continue to grow and water demand rises.
Researchers led by the U.S. Geological Survey, reporting this week in Science, wanted to see if these recent trends are truly unprecedented. So they created snowpack histories for three regions—the upper Colorado, the Northern Rockies and the greater Yellowstone area—by using 66 tree-ring chronologies. Trees record in their patterns of growth (i.e., tree rings) the amount of water available to them during the growing season. In the West, that water is largely controlled by the amount of water in the snowpack, and by concentrating their tree-ring data on trees from areas where the precipitation comes mostly in the form of snow and on trees known to be most sensitive to the snowpack, the scientists were able to create a good record of snowpack levels in the area going back to around 1200 A.D.
The record has plenty of variability—snowpack levels are dependent on many different variables, such as sea surface temperatures, that aren’t consistent from year to year. But around 1900, two of the three regions underwent a major decline in snowpack, and then all three dropped precipitously starting around 1980. “Over the past millennium, late-20th century snowpack reductions are almost unprecedented in magnitude across the northern Rocky Mountains,” the scientists write. The culprit? “Unprecedented springtime warming due to positive reinforcement of the anthropogenic warming by decadal variability.” Translation: climate change.
Last year when I was reporting my story on the Colorado River, Patricia Mulroy, who manages Las Vegas’s water, told me that we need a new attitude about water, especially in the West. “It’s not abundant, it’s not reliable, it’s not going to always be there,” she said. How many times do we need to be told before it sinks in?
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I thought tree ring thickness was determined by length of growing season and thus was a proxy for temperature. It tells us about available water as well? How do they sort out a longer, drier growing season from a shorter, wetter one? Is there a qualitative difference in the tree rings?
I’ve learned fairly recently just how little people like to listen to anything that doesn’t directly affect them. And often-times that counts in to things that directly affect them. Suffice it to say, we will probably never truly adjust our attitudes on the environment as a species, even after we’ve caused a global emergency. (Though I’d say we qualify for one already.)
Basically, upper-elevation tree rings are affected by temperature more than water, and lower-elevation tree rings are the other way around. So by comparing trees from different areas at the same time, you can determine how much is from water availability and how much is from temperature.
Upper elevations and lower elevations can have radically different temps and rainfall, so the study basically means nothing at all. “A new study shows” is propaganda. No real scientist would stand behind findings unless they were replicated over and over again after being subjected to massive peer review. This study fails every possible scientific test for significant finding.
Really? People are willing to believe this stuff? I live in Wyoming, the snowpack was unprecedented this year all right, in the way that there was so much of it, it became immeasurable! Especially in the Rockies, their snowpack was estimated to produce over 2 million acre of water this year…there is flooding all over the place here in Wyoming because of so much snow…for the first time in memory certain seasonal roads couldn’t open in time because they couldn’t clear it fast enough since it was even more heavy and wet than usual…sure a few years back it was different…but it’s called a drought…it happens to a lot of places…apparently the writer prefers speculation over what is actually happening.
One winter of unusually heavy snowfall is unlikely to erase a trend covering decades. I’ve written before about the difference between climate and weather (http://blogs.smithsonianmag.com/science/2009/08/weather-vs-climate/). It’s very easy to look at the most recent weather events and think that it will always be like that. But only by looking at changes over long time periods and over large areas (that’s climate), can you see real trends and get a picture of where things are going. And it’s those climate changes that make people worry.
hmm well then it is really sad that signs of anthropogenic warming have been happening since the 1900′s and no one took a step back to change things/attitudes about climate before it became too bad…what was causing it back then? Is anyone doing anything about places like Las Vegas using water for things other than what it’s needed for?