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Bougainvillea lines the winding roads across San Diego, including near where Hanna grew up. (Hanna Webster for The Xylom)

Heat Waves, Wildfires, and Downpours: San Diego is Changing and Climate Change is One Culprit

Fuchsia bougainvillea and scarlet trumpet vines drip over the fences on the winding road toward the house where I grew up.


Reaching the crest of the hill, the lush valley of San Diego's North County stretches toward a silver strip of the horizon—the ocean, gleaming, at what looks like the edge of the world. Eucalyptus trees shed their ashy scythes onto the rough blacktop, hot to the touch. Growing up, our side yard was home to avocado and orange trees, generous with their bounty and thriving in near-tropical temperatures that rarely dipped below 50 degrees Fahrenheit (10 degrees Celsius). In the summer, a pitcher of fresh-squeezed orange juice often sat on the ivory tile of our kitchen counter. My siblings and I were sent to wrestle with the avocado picker, twice as tall as us and leaning precariously out over a patch of grass we feared was slithering with rattlesnakes. Now, the orange tree suffers, likely ridden with a blight of citrus-killing disease and choking from drought. When I returned home after seven years in the Pacific Northwest, the hometown I grew fond of had changed—and climate change was one culprit.



While scientists have warned of the impending climate disaster for decades, these events have begun to manifest in real-time. Local residents have been exposed to heat waves, wildfires, and smoke time and time again. A 2020 paper published in Geophysical Research Letters by climate scientists at UCLA states that California has been experiencing more extreme weather patterns by way of more concentrated precipitation. An unfortunate series of events caused by drought can lead to increased flooding when it does rain. According to Drought.gov, 100 percent of San Diegans are affected by the current drought. Combined with existing crises of COVID-19 and inequity, this is an environmental, agricultural, and public health disaster brewing on the boundless Pacific horizon, threatening vulnerable communities the most.


 

When I moved back home in September of 2021, I flew into a heat wave. It is not uncommon for September and October to be hot in Southern California, but last year the thermometer pushed 90 degrees, and 100 in more inland areas. A weather forecaster in an article from The San Diego Union-Tribune said daytime temperatures during this heat wave were about seven degrees above normal.




Heat waves during the fall season receive their fair share of attention because of how dangerous they are: when 90-degree days become 100-degree days, we can’t release our body heat through sweating, resulting in heat strokes that can endanger the population. Dry and hot environments make wildfires worse. However, heat waves during the winter can be overlooked because cool 40-degree days becoming mild 50-degree days isn’t life-or-death. Across the Southern California coast, winters are heating faster than summers, with abnormally hot days in the winter happening more than twice as often than in the summer.



Warmer winters mean that some crops do not get the necessary chilling time, ultimately yielding smaller harvests. This also means pests and diseases can spread faster, plants get confused, or the heat straight up kills crops. Take the notoriously fickle avocado as an example: A 2018 study carried out by researchers across various University of California institutions and published in the journal Agronomy predicted that by 2050, avocado yields could decline by 40 percent. This is alarming not only because San Diego County has over 5,000 farms, more than any other county in the United States—many of them being small, family-run farms—but also, San Diego County leads the state and nation in the annual production value of avocados at a whopping 153 million dollars. My father, whose sprawling garden boasts 12 beds, has given up on growing lettuce because the perpetual heat prevents it from thriving. Lettuce thrives between 70-80 degrees, but can only tolerate a few days of 80-85 degree temperatures.


 

On the other hand, a perfect storm brews when wildfires blaze across the state concomitantly with hot Santa Ana winds during the hot and dry season. Tarik Benmarhnia is an environmental epidemiologist with a joint appointment at UC San Diego’s Scripps Institution of Oceanography and the Herbert Wertheim School of Public Health and Human Longevity Science. He studies how environmental science, epidemiology, and public health together can inform the impact of global climate events. In 2021, he was involved in a study on Santa Ana Winds published in the journal Climate Dynamics.




Benmarhnia and his colleagues looked at two “flavors” of Santa Anas: Hot Santa Anas are dry desert winds that blow in from the Great Basin, an area that covers most of Nevada and some of its surrounding states. Not all extreme heat events along the Southern Californian coast are caused by hot Santa Anas, but the two are moderately correlated, and hot Santa Anas exacerbate the worst effects of heat waves when they both occur. Cold Santa Anas are named so because of the extreme cold they bring from a more northerly direction in the Pacific Northwest, preceded by widespread precipitation over the West and accumulation of snow over the Great Basin.