Early Snowmelt Ignites Global Warming Worries
There was no shortage of snow here last winter.
But under a withering sun, the snowmelt started in mid-March, in what appears to be one of the earliest onsets in almost 90 years. Some scientists suspect it is another sign that climate change is eroding the Sierra Nevada snowpack, the state’s main source of water.
“This is not what you would expect to see in June,” said researcher Jessica Lundquist of the Scripps Institution of Oceanography, as she measured the flow of the Tuolumne River on Saturday. “This is very low. This is a July measurement.”
Research elsewhere in the West points to the same phenomenon: As temperatures have grown warmer over the last 50 years, less snow is falling in some places and it is often disappearing one to three weeks earlier.
Stream gauge data of the Merced River from 1916 to the present show a shift in the onset of the melt from mid-spring to late winter or early spring over the last two decades, said Dan Cayan, director of the Climate Research Division at Scripps and a researcher with the United States Geological Survey. In 10 of the last 20 years, the melt began on or before April 1.
Scientists have long known that a change in the climate could result in declining snowpacks, but in recent months evidence has emerged that it appears to be happening.
“The mountain ranges are essentially draining and drying earlier,” Cayan said. “I would say there’s enormous concern about this.”
Mountain snowpacks have long served as a storage tower for the West, slowly releasing water -- and creating hydroelectricity -- in the hot, dry summer months, when the needs of cities and farmers are greatest.
California water managers are now grappling with a tough scenario. In winter, reservoirs must be kept low to provide flood control for cities. As a result, there is no place to store the water if it comes rushing down earlier in the year, meaning it could be allowed to flow to the ocean.
“Is this a short-term cycle or is it longer? That’s the big question, and everyone’s looking for the answer,” said Frank Gehrke, the chief snow surveyor for the California Department of Water Resources.
The average global temperatures of the last two years were tied for being the second warmest on record since the late 1800s, when data were first collected, according to the National Oceanic and Atmospheric Administration. United Nations data show the 10 warmest years on record have been since 1990.
Philip Mote, a research scientist at the University of Washington, testified to Congress earlier this year that snowpacks were down an average of 11% across the West since the 1970s.
Mote has also found that snow accumulations at more than 200 sites in the West were down since the 1950s. That included sites in the Sierra, Cascade and Rocky mountains -- the three ranges that define the West and supply the bulk of its water.
Idaho legislators brought him to Boise this spring for a consultation on how global warming might impact their state. Idaho “is a state that has been in the camp that there isn’t global warming, and if there is, it’s going to be good,” Mote said.
Many scientists -- Mote, Cayan and Lundquist included -- are reluctant to pin the heat wave that ignited the early melt this year solely on global warming. The reason is that weather in the West is notoriously fickle on a year-to-year basis.
Scientists also said that this year’s weather fits into a larger trend of warming temperatures -- with more rain and less snow -- that can be seen in data collected over recent decades.
“There is a chance that all this will be covered with snow this time next year,” said Lundquist as she tromped along the Tuolumne River. “But I can also say there’s a greater probability that there will be less snow over the next 20 years.”
On Wednesday, the National Center for Atmospheric Research in Boulder, Colo., said new calculations show that global temperatures will rise by nearly 5 degrees Fahrenheit in coming decades if carbon dioxide is released at its current rate by the burning of fossil fuels.
Although many scientists agree that global warming is occurring, disagreement remains over the cause.
Some, like Lundquist, believe fossil fuels are the culprits. Others blame natural fluctuations in the climate.
Bill Patzert, an oceanographer at the Jet Propulsion Laboratory in Pasadena, believes the Earth is growing warmer because people have drastically altered the landscape, by paving cities and leveling rural areas for farms. Yet, Patzert also said that the cause of warming is somewhat of a moot point because there are sufficient data showing that snowpacks are melting earlier. “The bottom line is we better start using our water more wisely,” he said.
Water agencies are already trying to find ways to store more water.
“I don’t know if global warming is happening or not, but I’ve been in the business for 25 years, and in the more recent years nothing seems to be normal anymore,” said Mario Santoyo, the environmental and facilities manager for the Friant Water Users Authority, which provides water for 15,000 farmers in the San Joaquin Valley.
Santoyo said his district is pushing the federal government to build another giant dam upstream of the existing Friant Dam on the San Joaquin River. The idea, he said, would greatly increase the district’s capacity to catch snowmelt runoff while still providing flood control for Fresno.
But Santoyo acknowledges that a new dam on the San Joaquin -- or anywhere else -- would be enormously controversial with some environmentalists, and he predicts a future of even more fighting over water.
Environmentalists have long opposed dams, arguing that the structures destroy important wildlife habitats and serve only to allow farmers and urban users to continue wasting water.
The Metropolitan Water District, which provides water to more than 18 million Southern Californians, is facing two problems.
The Sierra snowpack appears to be melting earlier, while another major water source, the Colorado River, is in a drought that appears to be the region’s worst since 1590 to 1594, according to the U.S. Geological Survey.
Adan Ortega, an MWD vice president, said the agency began consulting experts on global warming several years ago. Each told the agency the same thing: Hoard more water in the good times, and store it for the bad.
In that spirit, the water district has well over two years of water supply in reservoirs and aquifers.
Lundquist hopes to build computer models that will help water managers at the MWD and other districts better understand the timing of future snowmelts. Using an array of devices, she is collecting data that will reveal where and when the snow is melting.
She counts herself as lucky to work in the park but also said that she’s increasingly alarmed at the changes that may be taking place that will affect people, as well as plants and wildlife.
“My parents brought me up here every summer when I was a kid,” said Lundquist, sitting on the banks of the Tuolumne. “And when I have kids I want to bring them here. But at one point I don’t think we’re going to need the down sleeping bags.”
