The Los Angeles Times reminded readers on Monday that when Governor Jerry Brown ordered water restrictions on April 1, this year, he was standing in a Sierra Nevada meadow that should have been covered in 5 1/2 feet of spring snowpack.
The snowpack this spring was just five percent of the average for the second half of the century, according to researchers at the University of Arizona. The scientists say their findings indicate “the 2015 low is unprecedented in the context of the past 500 years.”
“We were expecting that 2015 would be extreme, but not like this,” said senior study author Valerie Trouet, a paleoclimatologist with the study. This latest study is one of a number of studies that have tried to explain and make sense of the depth of the four-year drought and its place in the broader context historically.
This study is a little different than past studies that used data from tree rings and other sources to approximate temperatures and snowfall amounts. This research looked specifically at the Sierra Nevada’s snowpack, along with tree ring data and past records on Temperatures, rainfall and snow levels.
The record-low snowpack, along with increased temperatures and low precipitation altogether, “suggests that the occurrence of much reduced snowpack is likely to be less rare in the future than it has been over the past half-millennium or longer, meaning less storage of water as snow,” Eugene Wahl, the co-author of the paper and scientist at the National Oceanic and Atmospheric Administration, told the Huffington Post.
NOAA’s NASA satellite images dramatically illustrate the difference in the snowpack amounts from 2010 and 2014. In 2010, the Sierra Nevada’s had an average amount of snowfall, and in 2014, it is quite different.
Snowpack is key to California’s water supply. The melting Sierra Nevada snows replenish the state’s reservoirs and supply roughly one-third of the water needed. Because of this dependence on snowpack, its levels have been monitored since the 1930s, and include 108 monitoring stations throughout the Sierra Nevada Mountain range.
When researchers compiled all their data, they discovered the “snow drought” this year was unprecedented because it affected the whole mountain range, something that shouldn’t be seen but once in every 500 years. Valerie Trouet, one of the authors at the University of Arizona, told Reuters there are reasons to believe that man-made global warming “played an important role in the 2015 snowpack low.”
“With anthropogenic warming, those high temperatures are going to be rising,” Trouet said. “We can assume that the return interval is going to get shorter.”
This study was published in the journal Nature Climate Change on September 14, 2015, and entitled: Multi-century evaluation of Sierra Nevada snowpack.
