Hotter and drier – these are the new standard for Southern California.
The warmer, especially late summer and fall months, and especially the drier November and March, traditionally mark the beginning and end of the region’s rainy season. Also more triple-digit temperatures every year.
That assessment comes from the National Oceanic and Atmospheric Administration, which recently updated “normal” weather at thousands of locations across the country. The new criteria based on the 1991 to 2020 season replace the old criteria based on the conditions from 1981 to 2010.
The Southern California Newsgroup analyzed data from 68 stations in Los Angeles, Orange, Riverside and San Bernardino counties that had both temperature and precipitation criteria for both eras, to compare how “normal” is changing.
“Southern California has a lot of warming and a lot of dryness, that’s for sure,” said Michael Palecki, project manager for climate parameters at NOAA’s National Center for Environmental Information.
Those concerned about the effects of climate change, Palecki said, “are rightly concerned with the situation we are facing.”
Michael Jarrett, co-director of UCLA’s Center for Healthy Climate Solutions, hopes that as people begin to notice changes in weather patterns and experience more extreme events, they not only believe in climate change Rather do something about it.
“I think all these things are reaching people. People are starting to realize that climate change is not a hoax,” he said. “It is not a hoax, it is real and it is happening.
“We have to influence the behavior of millions and millions of individuals,” Jarrett said. “People think this is a serious problem, and I think they’re starting to feel that way.”
more heat waves
In case you didn’t enjoy the heat waves that swept Southern California in June and July, the new benchmarks include some bad news: An average of 68 weather stations analyzed, nearly five more 100-odd than previously reported in the region. Degree days are visible. .
It’s worse in the desert.
Twentynine Palms formerly experienced approximately 63 triple-digit days per year. According to the new weather norms, it has now increased to 89. This represents the largest increase of any station analyzed, but one of the two stations, Joshua Tree and Barstow, is also getting 20 more triple-digit days than before.
Woodland Hills now has about 36 triple-digit days per year, compared to 21 days previously. The numbers nearly doubled in Van Nuys (from eight to 15) and Chino (from 13 to 23).
Of the 68 stations, 59 are seeing 100 degrees longer than the day before, while seven – all near the coast or in the mountains – remain unchanged. Only two in San Bernardino County – Victorville and Trona, are both seeing less.
(Maximum 100-degree days? The new normal is 131 of them per year at a station in Blyth near Riverside County’s border with Arizona, up from the old norm of 121.)
Heat waves are “one of the leading causes of weather-related deaths in the United States,” According to US Centers for Disease Control and Prevention. CDC shows data hundreds of people die years from heat-related illnesses, including 600. more than in California from 2010 to 2019.
Studies have shown that extreme heat has all kinds of other negative effects on people, UCLA’s Jarrett said. For example, work-related accidents — not just heat-related, but accidents of all kinds — increase and academic performance goes down, he said.
Even outside extreme heat events, Southern California is warming, new norms show.
Average annual temperatures – which take into account the fluctuations of each day of the year – increased at 67 of the 68 weather service stations analyzed. The only exception was Tustin Irvine Ranch Station, one of two near Great Park in Irvine, which is 0.6 degrees cooler than before. (The other Irvine Ranch station, however, is 0.9 degrees warmer than the first.)
Other stations range from 0.3 degrees warmer in places like Pomona and Wrightwood to 1.6 degrees warmer in Hemet and Ontario, with the biggest increase being 1.7 degrees at one of Riverside’s weather stations.
The average increase in the 68 stations analyzed is 0.7 degrees.
That may not sound like much, but there is actually a “quite substantial rate of growth,” Palecki said. He noted that the 20 years in the ages covered by the old norms and the new norms are the same.
“You’re really looking at the difference between 1980 and 2010 divided by three,” he said. In other words, an increase of 0.7 degrees between the two eras means that 2010 was 2.1 degrees warmer in Southern California than it was in the 1980s.
“So that means we’re growing really fast,” Palecki said.
And as Jarrett pointed out, “We’re not going to see it affect all people equally.”
The people most vulnerable to the effects of increased heat are people with pre-existing health conditions, the elderly, socially isolated people, and black and Latino communities, he said.
Not only are people in low-income and minority communities less likely to have air conditioning and more likely to have pre-existing conditions, but Jarrett said it does happen in their neighborhoods. low green space And more structures and concrete, which really makes them hot.
In fact, a UC San Diego study released in July found that the land surface may warm up to 7 degrees in high-poverty areas compared to the wealthiest areas in the same county.
The new criteria show that each month of the year has warmed slightly in Southern California, but the heat continues to drop further toward the end of the summer – with the months of August to November rising by an average of 0.9 to 1.0 degrees Celsius. The lowest increase was seen in May at 68 stations, only 0.1 degrees.
Breaking down by geography, temperatures increased most at inland stations—those more than about 5 miles from the coast but south and west of the mountains—at stations closer to the coast, in the mountains, or in the desert at the other. towards the mountains.
July and August are Southern California’s hottest months, but how hot it is varies by location. July’s new normal high is 69.4 degrees at the Santa Monica Pier, but more than 100 at most desert stations, and 110.5 degrees in the needles.
Looking for some chilly weather? Go to the mountains for the area’s lowest average temperature. For example, in Big Bear Lake, normal lows remain below freezing for half the year.
Less rain (and snow too)
The new standards show that on average the 68 weather stations are getting about 0.9 inches less rain each year.
This shortfall is not spread evenly throughout the year. March and November are each receiving about a quarter of an inch less rainfall, while April, August, September and October are each falling by about a tenth.
Only eight stations are receiving more rain than ever before, and half of them are getting a few hundredths of an inch more. Sandberg, in the far northwest corner of LA County, is about eight-tenths of an inch up, the Getty Center about 0.6 inches and Van Nuys up 0.4 inches.
On the other end of the spectrum, a station at Mount Wilson is receiving 3.8 inches less rain, and airport stations in Burbank, Ontario, Chino, and Riverside also show at least 3 inches of drop.
Only 13 stations analyzed had snowfall data. On average, they are getting an inch less snow per year than before.
The biggest drop was at Big Bear Lake — home to several ski resorts — whose normal annual snowfall dropped from 65.7 inches to 58.6 inches.
Wrightwood, which also offers skiing, is now snowier than Big Bear, according to NOAA data. Its new normal snowfall is 61.8 inches per year, a slight drop from the earlier 62.3 inches.
‘Perfect conditions for wildfire’
The timing of hot, dry conditions is particularly unfortunate for wildfire season. Less rain in March means vegetation may begin to dry out sooner, warmer fall temperatures can turn more vegetation into wildfire fuel as destructive Santa Ana winds come and a dry November means less rain. Helps to resolve conflict.
“They are certainly the perfect conditions for wildfires,” said Tirtha Banerjee, assistant professor of civil and environmental engineering at UC Irvine, who studies how fires move.
Climate change certainly isn’t the only factor in the increasing destructiveness of western wildfires – more people are living and visiting wild lands, which increases the risk, and people have been suppressing wildfires for so many years. There is an abundance of fuel to burn.
But the cycle of warmer temperatures and dryer conditions increases wildfire risk “substantially,” Jarrett said.
“I don’t think it’s a doomsday,” Banerjee said. “We have to start with the fact that fire isn’t necessarily all bad.”
Many ecosystems depend on fire, he said, so wildfires are not a disaster if they are not threatening people.
The question should be, “How do we live with fire?” Banerjee said. “We can’t afford to lose life or property, so how do we manage ecosystems better?”
One answer is more determined fires, which he said would reduce the amount of fuel available to burn in wildfires and, in turn, reduce their intensity. Engineers can work to “harden” infrastructure so it has less risk of burning, and officials can help communities be more prepared.