On May 4, the entire Central Coast reached a D2 (Severe Drought) classification. I assumed our region would remain at this level through the summer since we had moved into our historically dry season of May through September. However, by early June, most of the state of California transitioned to either an Extreme Drought (D3) level or D4 (Exceptional Drought) classification, the most severe category, an unprecedented rate of increase.
This drought is not only rearing its ugly head in California but impacting the entire western United States. I have never seen such a dramatic increase in drought harshness over such a short period. I have been closely watching this index for more than two decades.
The U.S. Drought Monitor says it determines the severity of a drought utilizing the “Palmer Drought Severity Index, the Standardized Precipitation Index and other climatological inputs; the Keech-Byram Drought Index for fire, satellite-based assessments of vegetation health and various indicators of soil moisture; and hydrologic data, particularly in the West, such as the Surface Water Supply Index and snowpack.”
Why did the Central Coast’s drought level change so dramatically?
Of course, the main reason is the well below-average precipitation over the past two years. We depend on the rain and snow to fill our lakes and reservoirs and recharge our groundwater basins and aquifers. In fact, we experienced the driest back-to-back Februarys in 152 years of rainfall records at Cal Poly, historically the wettest time of the year.
Another crucial factor late in the rainy season also played a role in the rapid increase in the drought classification: the dramatic warming of overnight minimum temperatures, especially in the Sierra Nevada mountains.
Over the past 54 years, the daily minimum temperatures for PG&E’s Lake Spaulding Climate Station have drastically increased. The station is at an elevation of 5,160 feet along Highway 80 as you head to Lake Tahoe. The eight-year moving average over a 41-day period from June 1 through July 11 of each year reveals a significant warming trend.
From the 1970s through the 1990s, the average daily minimum temperature remained around 43 degrees Fahrenheit, plus or minus one or two degrees. From the year 2000 onward it has rapidly increased, reaching 49 degrees this year
These much warmer-than-average minimum temperatures produce earlier snowmelt and more evaporation from the lakes, reservoirs, soils and plants — worsening the drought severity.
At Paso Robles Municipal Airport, the normal low temperature in June is 49.8 degrees. This June, it was 53.7 degrees. Typically, San Luis Obispo County Regional Airport’s normal low temperature in June is 51.2 degrees, this June, it was 54.8 degrees. There was a day in June where the overnight low never got below 72 degrees in Paso Robles.
Not only are these warmer-than-normal temperatures exacerbating the drought, but they’re also impacting our health — especially the health of those in underserved communities without the resources to purchase air conditioners or take trips to cooler regions such as Central Coast beaches.
I attended the American Meteorological Society Broadcast Meteorology Conference in San Diego in June 2019. One of the speakers was physician and climate activist Dr. Bruce Bekkar, who I found particularly thought-provoking.
“The current human cost of climate change in America is not limited to the death tolls of headline-grabbing superstorms, floods and heatwaves,” he told us. “Although extreme weather events are increasing, evidence now clearly connects our global warming to additional, more prevalent dangers, including warmer average temperatures, worsening air pollution, new infectious agents and acute and chronic stress.”
Bekkar said that it is not just the heat waves that are causing problems but also the warmer overnight conditions that aren’t allowing people to cool off, adding significantly to their stress. “Hospitalizations due to cardiac problems increase about 5%, and respiratory conditions rise 6% for every day that is 10 degrees warmer than typical in Southern California, or for example, a day with 80 degrees temperature versus 70 degrees,” Bekker said.
Bekker said that when he attended medical school back in the1980s, he only spent two hours over four years studying tropical infectious diseases because students were told they would never see them unless they moved to the lower latitudes toward the Earth’s equator.
Since the time he attended medical school, tropical infectious diseases have spread northward. Today, many of those tropical diseases are now occurring in the United States. For example, the first case of the West Nile virus in the country happened in the Midwest back in 1999 and has since spread west, north and east to most of America, with the first occurrence in California in 2002. Tragically, a resident in San Luis Obispo County died from complications of West Nile virus in July, according to Dr. Penny Borenstein, San Luis Obispo County public health officer. It was the first death from the mosquito-borne disease in San Luis Obispo County.
Another tropical disease that seems to be propagating northward is dengue fever. The illness is spread by the bite of a mosquito and was previously only found in the tropics. Unfortunately, it has now been spotted in Florida and Texas.
Bekkar ended by saying, “Even though it will get worse before it gets better, by reducing the amount of fossil fuels we burn, for example in automobiles, we will see a rapid increase in air quality, which will improve everyone’s health.”
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