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WE®: How Climate Change Is Affecting California

Climate scientists forecast hotter and drier conditions for the state as the climate crisis continues.


(Ed. Note: This post was lightly updated on March 17, 2022 to provide additional information on Climate Reality’s upcoming, free, in-person climate advocacy training in Las Vegas, Nevada from June 11-13, 2022. For further information or to apply for the training today, click here.)


From lush vineyards, relaxing beaches, and beautiful snowcapped mountains to the vast studio lots where movie magic is made, California is one of a kind. The state is best known for its extraordinary natural beauty and laid back perspective, but it’s increasingly making headlines for a different reason altogether. Namely, the many ways our warming climate is transforming the environment.


Over the last several years, the recurring drought situation in California has been getting all kinds of media attention – and for good reason. From 2012 to 2016, the state experienced one of the worst droughts in its history. And it took the wettest winter in a century in California’s northern Sierra Nevada mountains to rescue the state from the prolonged dry spell.

The recent relief may prove short-lived: Climate scientists forecast hotter and drier conditions for the state as the climate crisis continues.

And in California, which gets about 75 to 80 percent of its freshwater from the Sierra Nevada snowpack, that combination of rising temperatures and decreasing precipitation, particularly in the winter and early spring, could prove especially dangerous.

“The Sierra Nevada snowpack functions as the most important natural reservoir of water in California. Under current conditions, the snowpack is created in fall and winter and slowly releases about 15 million acre-feet of water in the spring and summer, when California needs it most,” according to the California attorney general's office. “California’s dams and water storage facilities are built to handle the snow melt as it happened in the past. Higher temperatures are now causing the snowpack to melt earlier and all at once. Earlier and larger releases of water could overwhelm California’s water storage facilities, creating risk of floods and water shortages.”

(Assuming there’s even snow to melt: Earlier this year, after “an historically dry December,” the snow-water equivalent (SWE) of the northern Sierra Nevada snowpack was at just 27 percent of its multi-decade average.)

It’s important here to remember how truly global climate change is – because part of California’s precipitation woes could come down to a phenomenon happening half a world away in the Arctic. 

A recent study, conducted by scientists at Lawrence Livermore National Laboratory and published in the journal Nature Communications, discovered a link between diminishing Arctic sea ice and the buildup of high ridges of atmospheric pressure over the North Pacific. In short, California’s rain and snowfall are sensitive to both tropical and mid-latitude atmospheric circulation changes – and these ridges are effectively pushing storm tracks away from the state.

“Using complex new modeling, the scientists have found that rapidly melting Arctic sea ice now threatens to diminish precipitation over California by as much as 15 percent within 20 to 30 years,” the Los Angeles Times writes. “Such a change would have profound economic impacts in a state where the most recent drought drained several billion dollars out of the economy, severely stressed infrastructure, and highlighted how even the state most proactively confronting global warming is not prepared for its fallout.”


Wildfires have become more frequent and more severe across California in the last few decades, and the science behind why is pretty simple: Droughts dry out the land, killing plant life. All these dead and dried-out plants then act as tinder, igniting when the heat soars or lightning strikes or a careless cigarette butt is tossed in the wrong direction. And, with less predictable rains, once fires begin, it’s harder to stop them.

“Today's fire season in the western United States starts earlier, lasts longer, and is more intense than in the last several decades,” the attorney general's office writes.  “Wildfire occurrence statewide could increase several folds by the end of the century, increasing fire suppression and emergency response costs and damage to property.”

For a state whose 100 million acres are 80 percent covered by forest and rangelands, it’s an existential concern, particularly after last year’s devastating wildfire season. Several major wildfires burned their way across the state in 2017, including the largest-ever in California’s history, the Thomas Fire, costing the state a record high of $702 million in firefighting alone.

The Thomas Fire ignited in early December and burned about 281,900 acres, an area equivalent in size “to more than Dallas and Miami combined,” according to CNN. And while it may stand as the state’s largest, it’s not the only devastating one to strike recently:  Seven of California’s 10 largest modern wildfires have come in just the last 14 years.


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While drought and all that comes with it usually come to mind first when it comes to climate impacts on the Golden State, it’s important to remember California’s 840 miles of Pacific Ocean coastline – and the major flood risk it faces as sea levels rise.

About 85 percent of California’s more than 39 million residents live and work in coastal counties. And while the amount of sea-level rise the state can expect by the end of the century varies wildly from a low-emissions scenario to a high one – from one foot to 10 feet, respectively – one thing is looking more clear than ever: California is likely to see greater sea-level rise than the global average.

This has everything to do with changes in the rate and orientation of Earth’s rotation, gravitational fields, and crust,  according to an April 2017 study conducted by a seven-scientist working group of the California Ocean Protection Council Science Advisory Team.

Scientific American reports the team found “that the rate of ice loss from Greenland and Antarctica is increasing. [This] soon will become the primary contributor to global sea-level rise.”

For California, this increased melting, particularly in the Antarctic, could create something of a worst-case scenario, greatly increasing the amount of sea-level rise along its coast.

“For California, there is no worse place for land ice to be lost than from the West Antarctic Ice Sheet,” the study concluded. “For every foot of global sea-level rise caused by the loss of ice on West Antarctica, sea-level will rise approximately 1.25 feet along the California coast.”

By the end of the century, the state estimates that a 55-inch (4.6 feet) sea-level rise could threaten “$100 billion in property and infrastructure, including roadways, buildings, hazardous waste sites, power plants, and parks and tourist destinations.” While that 55 inches may sound exaggerated, it’s less than half of what scientists project could happen in an extreme sea level rise scenario.

And this doesn’t even include the cost of sea-level-rise-driven saltwater contamination of California’s freshwater delta and levee systems. The San Joaquin/Sacramento River Delta and the San Francisco Bay were found to be "particularly vulnerable to sea level rise and changes in salinity, temperature, and runoff” by the National Climate Assessment, meaning that as sea levels rise, the nearly 30 million Californians who use these systems could see their drinking water become contaminated with salt.


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There are numerous health consequences from drought, wildfires, and coastal flooding. Fresh drinking water could become more and more scarce as drought and warming combine to dry up reservoirs, rivers, and groundwater – or polluted floodwater runoff contaminates what they do have to offer. And, of course, fires can cause devastating direct injuries.   

But here, we’d like to focus on a few things we haven’t yet covered: namely the health impacts of extreme heat and air pollution associated with climate change.

Extreme heat elevates the risk of death from heart attack, heat stroke, organ failure, and more – and just last year, the state endured several record-setting bursts of it.

On September 1, San Francisco set an all-time heat record of 106 degrees – in what went on to become the state's hottest recorded summer, overall. Further south, as the Thanksgiving holiday approached, the Los Angeles area was gripped by a run of 90-degree Fahrenheit days, a full 20-plus degrees above the normal for late-November.

Average temperatures in southern California have already warmed about 3 degrees Fahrenheit in the last century.

“From 1950 to 1970, temperatures in Walnut Creek, for example, topped 100 degrees six days a year, on average. But from 2006 to 2016, there were nine days on average. And unless there are significant reductions in greenhouse gases, from 2030 to 2050 there will be 16 days a year over the century mark, and a sweltering 32 days a year by 2100,” the Mercury News reported, using information from a database of temperature statistics and C02 emissions scenarios created by the Scripps Institution of Oceanography and the University of Washington. “The numbers are similar for every other major California city.”

Californians should also expect to see an uptick in asthma and allergies right alongside these rising temperatures. The science here is true in many places around the globe: With rising temperatures, pollen seasons will start earlier and last longer. Plus, concentrations of ozone and particulate matter in the air (which contribute to asthma and allergy attacks) will increase.

“Californians already experience the worst air quality in the nation. Hotter temperatures lead to more smog, which can damage lungs, and increases childhood asthma, respiratory and heart disease, and death,” the state attorney general’s office cautions. “Certain segments of the population are at greater risk, including the elderly, infants, persons with chronic heart or lung disease, people who can’t afford air conditioning, and those who work outdoors.”


Luckily for Californians (and the rest of the planet!), the state is at the forefront of climate action in the US. Among elected officials, Governor Jerry Brown is “America’s de facto leader on climate change,” and the state will host a Climate Action Summit later this year in San Francisco to bring together “the leaders of states, cities, businesses, and others who made pledges to curb heat-trapping greenhouse gas emissions as part of the Paris accord.” 

The state’s leaders know the climate crisis threatens their future – and they’re taking action. But so are regular Californians up and down the state, pushing the envelope in everything from sustainable business to community-based clean energy.

Ready to take action and fight back when it matters more than ever?

Our upcoming Climate Reality Leadership Corps training in Las Vegas, Nevada from June 11-13 is a good place to start.

At Climate Reality Leadership Corps trainings, individuals ready to make a difference for our planet’s future spend three days working with former Vice President Al Gore and world-renowned scientists and communicators learning about the climate crisis and how together we can solve it.

Give us three days. We’ll give you the tools to change the world.