Sign In or Create an Account.

By continuing, you agree to the Terms of Service and acknowledge our Privacy Policy

Climate

The Flood-Filled Future of California

It does rain in Southern California after all.

The California flag, underwater.
Heatmap Illustration/Getty Images

More Californians have searched for news about “floods” in 2023 than “wildfires,” which seems in keeping with this summer’s series of out-of-left-field climate disasters. The worst smoke pollution hit … the East Coast. The deadliest wildfire in modern U.S. history leveled … a former wetland in Hawaii. Naturally a hurriquake in Los Angeles and catastrophic flooding in Palm Springs would come next?

But California’s reputation as the land of drought and fire has obscured the fact that extreme flooding is the other player in the state’s deadly climatological triumvirate. From the atmospheric rivers this winter, which caused some 500 mudslides and inflicted as much as $1 billion in damage, to Hurricane Hilary dumping record-breaking rains over the southwestern United States this weekend, floods are understandably top-of-mind (especially with a relatedly somewhat slow start to the state’s fire season).

Here’s what you need to know about the future of extreme floods in the Golden State:

Will California be hit by more hurricanes?

Former Hurricane Hilary was the first tropical storm to make landfall in California in 84 years, easily snapping the practically nonexistent late August daily rainfall records around L.A. In fact, hurricanes making landfall in the lower lefthand corner of the U.S. is so rare that there isn’t actually much of a data record for scientists to use as a point of comparison, Inside Climate News reports — which makes forming future projections and establishing links to climate change actually rather difficult.

What we do know is this: California has largely avoided hurricanes in the past due to the generally cold waters off its coast, which NBC News describes as acting as a sort of “shield” for the state. Hurricanes get their strength and moisture by forming over warm waters, and the eastern Pacific has historically been as much as 9 degrees cooler than the same latitude in the Gulf of Mexico.

But California’s shield has a crack. July was the hottest recorded month on planet Earth and the waters Hilary passed over on its journey north were 4 degrees warmer than usual, the Los Angeles Times explains. Sure enough, research shows that hurricane landfalls in the eastern Pacific could increase dramatically along with global and oceanic warming — bringing more rain and floods along with them.

There are certain conditions that made Hilary particularly unusual, however: A heat dome that formed over the central United States, for example, helped tug the storm directly over California, as opposed to a more typical path of a hurricane or tropical storm being pushed out to sea by easterly winds off the continent. So while hurricanes might be more intense and wet in the future, they won’t necessarily continue to make it over to California the way Hilary has.

Does El Niño have anything to do with floods in California?

Yes, to some extent. In addition to greenhouse gas emissions making the oceans warmer, the weather pattern called El Niño is likely responsible for some of the warming of the waters off of Baja California, which intensified Hurricane Hilary. But again, there were also unique conditions that contributed to Hilary’s unusual path over the southwestern United States, including the prevailing wind patterns. Strong El Niño years, as a result, don’t necessarily mean more hurricanes for Southern California.

El Niños have tended to bring higher winter rainfalls to Southern California, though that is also not necessarily a guarantee. NOAA’s outlook for the coming winter doesn’t currently show above-average precipitation expected for the state. Some El Niño years are actually drier than average, which goes to show that “El Niño is just one hand on the atmospheric steering wheel,” Weather Underground writes.

Why are we even talking about floods? Isn’t California in a drought?

California isn’t a land of droughts or floods — it’s a land of both. A better way to think about the future of weather in the state is as one of extremes.

That’s because, “[i]n a seeming paradox, drought and flooding are two sides of one coin,” Governing explains. “A warmer atmosphere can hold more water, and higher temperatures cause more water on the Earth’s surface to evaporate. This can result in bigger rainstorms.”

The good news is, most of California is now free of drought conditions and this year’s fire season has been quieter because of all the wet vegetation. But while Tropical Storm Hilary apparently only inflicted minor damage and no known deaths this weekend, floods have been a devastating fixture of life in the Golden State before and they will be again.

As Yale Climate Solutions warned earlier this year, “Given the increased risk [due to climate change], it is more likely than not that many of you reading this will see a California megaflood costing tens of billions in your lifetime.”

What is California’s worst-case flood scenario?

California doesn’t need 40 days and nights of rain to experience its worst-case flood event, researchers have found. If a 30-day rainstorm similar to one that hit the then-unpopulous state in 1862 were to strike again today, it could potentially be a $1 trillion disaster — “larger than any in world history” — UCLA’s “ARkStorm 2.0” scenario modeling found last year.

“Every major population center in California would get hit at once — probably parts of Nevada and other adjacent states, too,” Daniel Swain, a UCLA climate scientist and co-author of the paper, said in a statement at the time.

Unlike a tropical storm, which passes in a number of days, the ARkStorm flood event would last a month in the form of sequential atmospheric rivers, like the kind that battered the state this past winter. The link between climate change and heavy precipitation is well understood, and the researchers found that “climate change has already doubled the likelihood of such an extreme storm scenario,” with “further large increases in ‘megastorm’ risk … likely with each additional degree of global warming this century.”




Blue
Jeva Lange profile image

Jeva Lange

Jeva is a founding staff writer at Heatmap. Her writing has also appeared in The Week, where she formerly served as executive editor and culture critic, as well as in The New York Daily News, Vice, and Gothamist, among others. Jeva lives in New York City.

Climate

AM Briefing: Here Comes Alberto

On the tropical system in the Gulf, advanced nuclear reactors, and hybrid jet engines

Texas Is Bracing for the First Named Storm of Hurricane Season
Heatmap Illustration/Getty Images

Current conditions: Heat records are falling across the Midwest and Northeast while parts of the Pacific Northwest are seeing late-season snow • Wildfires in New Mexico have burned more than 20,000 acres • Nighttime temperatures remained near 100 degrees Fahrenheit in northern India.

THE TOP FIVE

1. Tropical storm takes aim at Texas

A weather system churning in the Gulf of Mexico could become the first named storm in what is expected to be a very busy hurricane season. Tropical Storm One, as it’s currently known, is “large but disorganized,” but is forecast to coalesce into Tropical Storm Alberto sometime today as it moves toward the coasts of Mexico and Texas and makes landfall tonight or tomorrow morning. A tropical storm warning was already issued for the Texas coast, indicating that high winds are on the way. Flash flooding is also very likely, especially across South Texas, where six to 10 inches of rain could fall.

Keep reading...Show less
Yellow
Guides

Did Climate Change Do It?

An extreme weather whodunit.

Sherlock Holmes inspecting a hurricane.
Heatmap Illustration/Getty Images

Maybe you’re reading this in a downpour. Perhaps you’re reading it because you have questions about the upcoming hurricane season. Or maybe you’re reading it because you’re one of the 150 million Americans enduring record-breaking temperatures in this week’s heat dome.

Whatever the reason, you have a question: Is this climate change?

Keep reading...Show less
Blue
Podcast

How China’s EV Industry Got So Big

Inside episode 20 of Shift Key.

Chinese EVs.
Heatmap Illustration/Getty Images

China’s electric vehicle industry has driven itself to the center of the global conversation. Its automakers produce dozens of affordable, technologically advanced electric vehicles that rival — and often beat — anything coming out of Europe or North America. The United States and the European Union have each levied tariffs on its car exports in the past few months, hoping to avoid a “China shock” to their domestic car industries.

Ilaria Mazzocco has watched China’s EV industry grow from a small regional experiment into a planet-reshaping juggernaut. She is now a senior fellow with the Trustee Chair in Chinese Business and Economics at the Center for Strategic and International Studies in Washington, D.C.

Keep reading...Show less