A shocking report released earlier this year predicts the Lake Tahoe snow season could decrease by as much as one to three months by the end of the century if greenhouse gas emissions are not reduced.

The report, Simulated Hydrologic Responses to Climate-Change Projections for the Lake Tahoe Basin, by Michael Dettinger, Ph.D. and Seshadri Rajagopal, Ph.D, was released by the Desert Research Institute in March. The study was commissioned by the California Tahoe Conservancy.

The study authors estimate temperatures around the lake may rise from 4 degrees to as much as 9 degrees Fahrenheit by 2100. The report predicts that a failure to effectively address emissions could cause the snowmelt in parts of Lake Tahoe Basin to “all but disappear” by the end of the century and “decline by about 80% in the rest of the Basin.” 

Those startling predictions are based on projections from eight different global climate models the researchers plugged into a hydrologic simulation of the Basin to examine two different future scenarios: one where climate action is taken to rein in greenhouse gasses and another where emissions continue unabated without intervention.

As the San Francisco Chronicle explained in an article examining the study last week, the report projects that “the loss of snow will be most severe on the north and east sides of the Tahoe basin,” including around popular Incline Village, and farther south toward South Lake Tahoe. Eagle and Cascade Creeks near Emerald Bay are projected to be “less impacted overall.” 

Also alarming, the “center” of snowmelt timing could arrive 20 to 50 days earlier in the year, which could cause the center of streamflow timing to also arrive about 20 to 50 days earlier on average “depending on locations and emissions.”

However, if climate action successfully reduces emissions, the basin snowmelt would face a less dramatic, but still concerning, 10 to 20 percent decrease.

Surprisingly, as the San Francisco Chronicle describes, the report predicted "flow of rivers and creeks overall… would not decline” because “total precipitation is not expected to change — just more rain instead of snow” is expected. The study estimates precipitation could increase up to 15% by century’s end.

“The increasing temperatures will result in warmer storms dropping more precipitation in large bursts, increasingly as rain rather than snow,” the Desert Research Institute explains in a summary of the study on its website that calls the study “the most detailed projections yet for how the region’s landscape will be impacted by climate change.” 

The study projects that year-to-year streamflow fluctuations will cause “increased episodes of hydrologic whiplash between drought conditions and flood.” And, those large streamflows carrying dirt and debris could pose a threat to Lake Tahoe’s world-famous crystal-clear blue water, the Chronicle reports.

Study author Michael Dettinger hopes that by comparing the Tahoe areas facing the greatest potential impacts with those expecting less impacts overall, the local communities can decide how to best focus their resources. According to the DRI website, Dettinger “hopes to work with web engineers to create a web app that can integrate the [study’s] data with GIS mapping and provide the climate projections in intuitive and useful ways.” 

“I believe that Tahoe is one of the few places that’s ready to do something to address the impacts of climate change,” Dettinger said. “We’ve got to figure out how to do this in a way that will actually benefit Tahoe.” 
The data is available at https://datadryad.org/stash/dataset/doi:10.5061/dryad.2v6wwpzrg.