New weather analysis says it’s getting hotter in Fresno and the Valley

In the San Joaquin Valley, where triple-digit summer temperatures are a fact of life, warmer-than-usual years are becoming the norm, a new National Weather Service report suggests.

Last year was the fifth-warmest year in Fresno since record-keeping began in 1887. And the top five hottest years in Fresno have all been in the past five years, the 2017 Annual Weather Summary said.

The trend is Valleywide. For Bakersfield and Hanford, the top four warmest years on record have occurred in the past four years, and Merced and Madera had their top five warmest years in the past six years.

It may be part of a global phenomenon. Last year was Earth’s third-warmest year on record, the National Weather Service announced Thursday.

No matter the cause, Fresno city officials are preparing for a future of higher average temperatures, said Tommy Esqueda, director of public utilities.

“We should all be planning that this is an ongoing, long-term pattern,” Esqueda said.

Under an executive order, “Making Water Conservation a Way of Life,” that was issued last year by Gov. Jerry Brown, cities in California must take steps to reduce water use.

On Jan. 1, the city launched its new outdoor watering schedule, Esqueda said.

One-day-a-week watering is allowed January through March, two days per week in April and May, three in June, July and August when lawns and landscaping have the highest demand for water, returning to two days a week in September, October and November, followed by one day per week in December.

Fines start at $50 for the first offense and go up to $200.

The water conservation message appears to be taking hold. Since the city went to water meters for all homes a few years ago, use has dropped from about 380 gallons per person per day to 224 gallons, Esqueda said.

“The governor wants even less than that,” he said. “Now we’re looking at getting it under 200 (gallons per person per day).”

Do the past five years of higher average temperatures signal that global warming is causing permanent climate change in the San Joaquin Valley?

Climate scientist Dan Cayan at the Scripps Institute of Oceanography in San Diego said climate change is causing some of the average temperature rise in California and the West, but not all of it.

“A major portion of the warmth during the last five years is attributable to natural fluctuations” of weather in California and the western U.S., he said.

However, “I believe the California warmth is likely receiving a boost from anthropogenic (human-caused) climate change,” he said.

Scientists are seeing a “recurring string of near-record annual global average temperatures,” as well as receding sea ice, melting glaciers and ice sheets, higher humidity, more extreme rainfall and warming oceans, he said.

The cause: Greenhouse gases pouring into the atmosphere, he said.

The Paris climate accord got nations to agree to reduce their greenhouse gas emissions, although President Donald Trump announced last year the U.S. would exit the agreement. California has its own greenhouse gas law to reduce emissions to 40 percent of 1990 levels.

Carbon dioxide is up 40 percent from pre-industrial times and other greenhouse gases are increasing, Cayan said. The “greenhouse blanket” of the atmosphere has gotten thicker, so it’s harder for the planet to cool, he said.

“A reasonable conservative guess” is that global temperatures are going up about 0.2 degrees Centigrade (0.36 degrees Fahrenheit) per decade, he said.

Last year in Fresno, there were 53 days in which the mercury hit 100 degrees or higher; 21 of those days were 105 or hotter. (The all-time record in Fresno for days over 100 is 63, set in 1984). In Bakersfield, there were 67 days in which the high temperature hit 100 degrees or more; 21 days were 105 or hotter.

Hot summers and higher average temperatures have the potential to disrupt farming, a key component of the region’s economy and identity, but local agricultural leaders aren’t too worried.

Dairy cow death rates climb during heat waves, for instance. A heat wave last year prompted officials to allow farmers to bury dead cows instead of having them hauled to rendering plants after the region’s main rendering plant in Kerman got backed up.

But the dairy industry is prepared for heat waves, said Paul Sousa, director of environmental services at Western United Dairymen.

In 2006, a heat wave killed an estimated 20,000 milking cows in the state, he said. “That year caused a pivotal change in the dairy industry,” he said. Farmers now use fans and sprinklers called “soakers” to cool cows and the air around them, he said.

“We’ve really reduced those loses,” he said. Last year, cow deaths climbed during a heat wave, but the problem was nothing like 2006, he said.

The spate of five years of higher average temperatures in Fresno is notable, said Ryan Jacobsen, executive director of the Fresno County Farm Bureau.

“If it’s in July and August, we’re prepared for it,” he said. “But when it’s in May, it can be problematic for sensitive and immature fruit.”

Hotter summer temperatures may not be as worrisome as the potential lack of cold temperatures in winter, said Marilyn Kinoshita, agricultural commissioner in Tulare County.

“Stone fruit growers are worried about chilling hours this time of year,” she said, because trees need cold weather for fruit to grow in spring.

In December and January there has been a notable lack of rain in the Valley. But the storm that arrived Friday is expected to lower overnight temperatures to the low 30s Saturday and Sunday in the rural areas of Fresno, Tulare and Kings counties.

This story was originally published January 19, 2018 at 2:01 PM with the headline "New weather analysis says it’s getting hotter in Fresno and the Valley."