Rainfall in Los Angeles

CLIMATE: Variability of local weather

With the current concerns about possible changes in global climate, unusual local weather events are cited often as circumstantial evidence of a change in the climate of the Earth. While earth scientists have identified twenty-nine separate regional climates on earth, climate in the largest sense is considered to be a global phenomenon, while weather is considered a local phenomenon. 

Just as variations in global climate are most meaningfully considered in the context of geological time that extends over thousands, millions, hundreds of millions, and even billions of years, local weather variability is most meaningfully understood in historical context over periods extending hundreds and even thousands of years. 

Author Joel Engel examines rainfall in Los Angeles in historical context, in an essay that appeared in The Wall Street Journal in March 2019 near the end of an unusually wet and rainy season in southern California. The article is reproduced here with the consent of the author. Readers can view it on the website of The Wall Street Journal by clicking here.

Los Angeles Dries Out After a Wild, Wet Winter: 

When it comes to precipitation in Southern California, there’s no such thing as “normal,” by Joel Engel, The Wall Street Journal, March 15, 2019.

 At long last, Los Angeles has been enjoying a rainy winter—over 18 inches of rainfall and counting, according to the National Weather Service. What a shock this must have been to Angelenos who could be excused for fearing that water falling from the sky had become a thing of the past.

“L.A. was not built in the desert, but the desert may be coming to us,” a Los Angeles Times editorial declared last November, echoing countless other media outlets. “We’ve had a worrisome number of dry winters.” 

Worrisome to whom? Only to those who believe that there’s anything “normal” about Los Angeles rainfall. The fact is that dry winters are the statistical norm. In 141 years of recorded Los Angeles weather history, 85 years (60%) have received below the NWS calculated average of 14.7 inches. Those dry years (measured July 1 through June 30) are counterbalanced by a smaller number of very wet ones, sometimes even biblically so—38 inches in 1884, and nearly that much in 2005. Only three times in that century and a half (1934, 1974 and 1975) have the recorded amounts been close enough for statisticians to call them “average” years. 

Still, that doesn’t deter the climate alarmists, especially those eager to tie the lack of rainfall to a supposed uptick in the number and frequency of damaging wildfires. “The desiccated ground beneath us was an important factor in the deadly Malibu and Woolsey fires,” a Times editorial claimed last year. That seems logical, since less than 5 inches fell in the 2018 season. But before Woolsey, the Santa Monica Mountains’ two most destructive blazes had been the Kanan Fire, which burned 25,000 acres and 230 homes, killing two, in Los Angeles’ fourth-rainiest year, 1978; and the Old Topanga Fire that burned 17,000 acres and 369 homes, killing three, in 1993, a year that enjoyed 27.36 inches—nearly twice the annual average.

But hasn’t climate change increased the length of dry stretches? That depends what you’re measuring against. Since 1877 there have been two five-year stretches (1987-91 and 2012-16) and one seven-year stretch (1945-51) of consecutive below-average rainfall. Of the 21 years between the 1944-45 season and the 1964-65 season, an alarming 17 years fell short of reaching the statistical average rainfall. Then, in 1969, the city was drenched by 27 inches of rain, twice the average. 

As a longtime L.A. resident, I consider it entirely fitting that our rain is as eccentric and unpredictable as the city itself. But that volatility plays into the hands of those who would purvey fear of drought. Today this is typically done for political gain, but in the past it was often done for financial gain.

In 1905, Los Angeles Times owner Harrison Gray Otis used his newspaper to campaign for a $1.5 million bond measure that would allow the city’s chief water engineer, William Mulholland, to study the feasibility of building a 240-mile aqueduct. The aqueduct would connect Central California’s Owens Valley to the north end of the San Fernando Valley—where, it just so happened, Otis and a consortium of associates (whose names now appear on Los Angeles streets and suburbs) owned thousands of acres of arid land. Stories in the Times flogged the risk of drought and warned of sand someday coming out of taps if new sources of water couldn’t be found. Given how rapidly the city was growing—from 9,000 residents in 1877 to more than 200,000 in 1905—it wasn’t a hard sell. The measure passed easily, though more than 19 inches of rain had fallen that year.

Two years later, in 1907, the Times published a rash of similar alarmist stories while pushing an additional bond measure that would raise $21.5 million to fund construction of the aqueduct. The measure passed, though nearly 20 inches of rain had fallen that year.

For the rest of the country, wild weather in Los Angeles may amount to nothing more than confirmation that almost everything about the place is odd. For Angelenos, it means we’d do well to consider “the end is nigh” warnings in historical context and enjoy the rain for as long as it lasts. After all, next year will probably be back to normal—you know, below average.