California snowpack data debunked: 2023 was no record year. And neither was 1952

Photo: Clouds pass above the snow-covered Sierra Nevada mountains, with Mammoth Yosemite Airport buildings standing below, in the wake of an atmospheric river event which brought heavy snow to higher elevations on March 12, 2023 near Mammoth Lakes, California. (Photo by Mario Tama/Getty Images)

That top honor should really go to 1983, which cinched first at 231% of normal, an analysis by the Bay Area News Group found

It was the snowpack reading that spawned a hundred headlines. “California ties 1952 record for all-time Sierra snowpack,” proclaimed KTVU. “California’s snowpack soars to record high after 17 atmospheric rivers,” trumpeted the Washington Post.

State officials largely seemed to agree. “As of right now, it’s looking like this year’s statewide snowpack will probably, most likely, be either the first — or second — biggest snowpack on record dating back to 1950,” Sean de Guzman, manager of the California Department of Water Resources monthly snow survey, declared the day of the official April reading earlier this month.

But this year wasn’t a record at all. It only appeared that way in large part because of the state’s shifting definition of a “normal” snowpack, which critics say obscures the true impact of climate change. And, in a closer look at the state’s seven decades of snowpack data, 1952 — the year atop the state’s data — wasn’t a record either. That top honor should go to 1983, which cinched first at 231% of normal, a new analysis by the Bay Area News Group found, when “normal” is considered the average dating back to 1950, the start of the state’s recordkeeping.

Over that period, 1952 is tied for second with 1969 at 226% of normal. This year actually came in fourth, at 222% of normal.

You won’t find those percentages in the California Department of Water Resources’ official records. But in an interview this past week, the agency didn’t dispute the data analysis behind the reordering that gives 1983 its due as the biggest, baddest Sierra snow year on record.

What explains this history redefining shift? Twin issues in how the state compiles the statewide snowpack figures are to blame.

So we ran the numbers, compiling 74 years of April snowpack data from over 300 locations called “snow courses” scattered throughout the Sierra, solving both issues plaguing the state data. The changes are not massive. But even small shifts can have an impact on scientific models. And they can change which year breaks a record. […]

Full article: www.mercurynews.com

Also see: The Science Behind Atmospheric Rivers