Is Bakersfield's climate changing? Is the entire southern valley getting warmer?
Yes. And no.
According to the National Weather Service's Hanford station, five of the past six years have been the five warmest in Bakersfield’s recorded history. Since the turn of the millennium Bakersfield has experienced nine years that were ranked, on average, among the warmest 20 since records started being kept in 1893.
Fresno, Bakersfield's cousin to the north, is seeing even more dramatic warming.
Brian Ochs, a meteorologist at NWS Hanford who compiles a wide range of statistics, found that the past eight years have been the warmest eight years in Fresno’s history.
One reason the average temperatures have been higher is because minimum temperatures have been higher, Ochs said. It's not that the maximum highs are getting hotter, it's that the overnight lows, on average, are not dipping as low.
"In terms of the annual average temperature at Bakersfield and Fresno, seven of the last eight years (or each of the years during 2012 through 2019, except 2013) have reached at least in the top 14 warmest years on record," Ochs said in an email. "The last eight years at Fresno have been the top eight warmest on record, while 2014 through 2018 were the five warmest for Bakersfield."
According to Ochs, annual average temperatures have been rising throughout California and much of the world, and are likely due to both natural and human causes.
"An example of a human cause is an increase in concrete and asphalt that tends to absorb much of the solar radiation and allow temperatures to warm, especially during the overnight hours (also known as the Urban Heat Island effect)," he said. "So, a lot of this warming is reflected in both daytime high and overnight low temperatures, although urban heat island studies tend to show a lesser extent in terms of the response to daytime high temperatures. Natural causes can consist of cycles in radiation directly from the sun, volcanic activity, and upper atmospheric phenomena."
A Caltrans report released last year, which focused on Kern County as well as Madera, Fresno, Tulare and Kings counties, evaluated risks, including extreme temperatures, increased precipitation, storm surge, wildfire risk and sea level rise.
"Climate change is an immediate and escalating threat to California and its transportation system, and Caltrans is being proactive," Caltrans Director Laurie Berman said in a statement. "We are looking at where the state highway system is vulnerable, so we can address issues moving forward."
Extreme weather events associated with climate change are already disrupting and damaging the state's roadway infrastructure and has potential for more severe impacts in the future, Caltrans concluded.
Climate models agree that California will become warmer. The increased temperatures mean more precipitation will fall as rain instead of snow, according to the state Department of Water Resources. And that has huge implications for water storage and availability.
Daniel Sumner, an ag economist at UC Davis, said researchers across the state are busy studying the changing patterns of California's Mediterranean climate.
"We don't look at the average annual temperature," he said. "It's not that interesting."
When it comes to the effect climate change could have on the Central Valley — California's fruit basket — Sumner said researchers aren't seeing changes in summertime high temperatures. Instead, they're seeing increases in wintertime lows.
The warmer nights are a "big deal," he said.
Not only do warmer nights limit the all-important chilling hours for some of the valley's most valuable crops, it opens the door to damaging pests.
"Winter cold controls some pests."
But the "big headline," Sumner said, is this: "Winter snow might fall as rain. If that happens, we aren't ever going to have enough reservoir space for it."