Professor Jeremy Pal: Less Water in California’s Future

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A projected increase of 3.6 degrees Fahrenheit (2 degrees Celsius) in the Southwest United States could cause an increase in the frequency and intensity of floods and droughts that would leave Southern California with water shortages in the coming decades, according to scientists at Loyola Marymount University and the Climate Change Science Institute at Oak Ridge National Laboratory in Tennessee.

In one of the most expensive and detailed regional climate modeling efforts, enabled by the fastest supercomputer (Titan) in the United States, researchers predict that by 2050, these rising temperatures will increase the amount of precipitation falling as rain rather than snow in the Sierra Nevada and Rocky Mountain ranges from which Southern California imports 60 percent to 70 percent of its water supply.

This phenomenon will make snowmelt occur earlier in the season, and reservoirs in the region will fill up earlier in the year, requiring the release of water in the winter for flood protection purposes. The result: In the summer, when the demand for water increases, less water will likely be available even during wet years.

In addition to the increases in heavy flood events, the study also projects an increase in the frequency and severity of drought conditions. Jeremy Pal, Graduate Program director and professor of civil engineering and environmental science at LMU and one of the lead researchers on the report, said: “Overall, average yearly precipitation amounts are not projected to change significantly by mid-21st century. However, given high year-to-year variability of California’s climate, increases in extreme wet and dry events, and snowpack reductions will critically impact water security of the region.”

Add to that a steep rise in the state’s population. By 2050, experts predict the population will increase by 30 percent. Brianna R. Pagán, one of the other lead researchers on the study, said, “Rising populations coupled with a lack of local water supply expansion could mean climate change impacts would leave the entire Southwestern United States more prone to water-supply shortages.”

In October 2015, Pal and co-author Elfatih A.B. Eltahir published a paper in an online edition of a scientific journal that indicated that climate change in the future could expose regional hotspots, such as in the Arabian Gulf area, that could severely affect human habitability because of rising temperatures.

Pal was also among the contributing authors of the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC). That work resulted in the IPCC’s sharing the 2007 Nobel Peace Prize with former U.S. Vice President Al Gore.

Jeremy Pal ’94 teaches classes in water resources, computer modeling and surveying. In 2009 and 2012, he led student groups that developed and installed a water filtration system in Malawi. Pal received a master’s of science degree in civil and environmental engineering in 1997 and a Ph.D. in civil and environmental engineering in 2001, both from MIT. In 2007, Pal co-authored a study that suggests that extremely hot days will increase by 200 percent to 500 percent in Mediterranean countries by the end of the 21st century if the current rate of greenhouse emissions continues.