Ski resorts, water supply could be threatened
May 9, 2003
TAHOE CITY — Mount Kilimanjaro could lose its famed snow-covered peak in the next 15 years. The Grinnell Glacier in Montana’s Glacier National Park has shrunk dramatically during the past 100 years. Could the Sierra Nevada be destined for the same fate?
According to two scientists at the Squaw Valley Institute’s speakers forum this week, the answer is yes. Due to a combination of global warming and natural causes, Western North America has been getting warmer for the past 50 years. While it’s doubtful the day would come when the Sierra sees no snow, the warming trend does have serious implications for California’s water supply and ski resorts.
The Squaw Valley Institute had its fourth in a series of environmental programs this week at the Resort at Squaw Creek. Dan Cayan, director of the Climate Research Institute at Scripps Institute of Oceanography, and Kelly Redmond, associate director of the Desert Research Institute’s Western Regional Climate Center in Reno, presented their studies on the long-range impact of global warming on the Sierra Nevada’s snowpack.
Since 1950, and especially after the mid-1970s, Western North America has experienced marked climatic changes. The region has warmed by 1 to 3 degrees Celsius, and extreme warm periods have become more frequent while the number of extreme cold days has declined. Tahoe City’s number of warm days from November to April, for example, has increased during the past 15 years, according to Redmond.
Global warming is caused by a combination of greenhouse gases, such as carbon monoxide, and natural shifts in the Earth’s climate, although scientists are not sure which is the greater contributor. They do know that the likelihood of reversing greenhouse gases in the atmosphere is slim, especially in light of increasing populations.
“This genie can’t be put back in the bottle,” Redmond said.
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This warming trend has caused the onset of spring to advance by five days to three weeks, Cayan said. A study by the University of Washington found that from 1950 to 2000, the state’s April 1 snowpack — which is usually at its peak — had diminished by an average of 38 percent.
Although elevations above 10,000 feet have warmed slightly since 1948, lower elevations have seen a greater loss of spring snow accumulation than higher elevations. This means there is not less precipitation but that the snow is melting faster. In fact, Cayan said precipitation levels have not changed that drastically compared to the rapid pace of the Earth’s warming.
The Sierra, with its eight rivers that drain on the Western Slope, is vital to California’s water supply. According to Redmond, almost all of the state’s water replenishment comes from the mountains.
“The mountains don’t occupy a large amount of land surface but they are hugely important for the West’s water supply,” he said.
Since the timing of California’s snowmelt is key for the state’s wells, a shortened winter season could mean less water during the summer months.
As an example, Cayan points to the Sacramento River, two-thirds of which flows into the Delta. Its April to July flow has diminished by 10 percent, which could seriously impact the Bay Area if the trend continues.
“Not only does the snowpack serve as an extra reservoir,” Cayan said, “but the snowpack is manageable because it’s released later after the snow season. It’s been a given Western communities have depended on.”
The Truckee River, by contrast, has only shown a marginal change compared to the Sacramento River because of its high elevation.
Cayan estimated that California will warm by 3 degrees Celsius during the next century. By 2090 he predicts the state could lose half of its late spring snowpack.
“We have a few decades, but it’s time to start thinking about (future water supply),” Cayan said.
In addition to the water supply, California’s shrinking snowpack could also affect ski resorts. While the biggest impacts will be seen at lower elevation resorts — those below 6,500 feet — the base areas of higher resorts could see a gradual loss of snow. The ski season will also likely be about a month shorter. The good news — the Sierra peaks will continue to see snow.
“The very highest places will probably get more snow as long as they stay below freezing,” Redmond said.
The bad news — the Southern Sierra may not have any ski resorts by the end of the century, which could mean longer lift lines in places like Tahoe.
“If you want to see snow in 2090, you will probably take a chairlift to look at some little patch of snow in the Southern Sierra,” Redmond said.