A MARTÍNEZ, HOST:
In the middle of the Pacific Ocean, a blob of warm water spanning thousands of miles is growing. El Nino is warming the ocean and will likely disrupt global weather patterns through early next year. Here's KQED climate reporter Ezra David Romero.
EZRA DAVID ROMERO, BYLINE: Climate scientists warn that one of the many effects of El Nino will likely be a 6-inch to 2-foot rise in sea levels this winter.
(SOUNDBITE OF SEA SWISHING)
ROMERO: That's a big deal for coastal communities like Pacifica, south of San Francisco, that already deal with extreme erosion and streets flooding during high tides. Christine Boles is Pacifica's mayor.
CHRISTINE BOLES: We have a lot that's vulnerable closer than 40 feet on the edge right now. It is terrifying.
ROMERO: Pacifica's 6-mile shoreline is lined with homes and businesses. The power of the Pacific Ocean recently cracked the city's pier and required the demolition of a beloved cafe.
BOLES: I was really surprised that it's happening now.
ROMERO: Pacifica is developing plans to deal with the rising water. But Gary Griggs, who specializes in coastal processes and hazards at UC Santa Cruz, doesn't think there's much the city can really do to stop the waves.
GARY GRIGGS: We can put in sandbags. We can bulldoze up sand berms. But we have really big waves and a really high tide. We're just no match for the Pacific Ocean.
ROMERO: Federal weather officials say there's an 81% chance of a very strong El Nino, and it could rank among the largest in modern history.
GRIGGS: And it's bigger and warmer than anything we've measured in the last century.
ROMERO: El Nino forms when tropical trade winds weaken, allowing warm ocean water near Asia to move toward the Pacific Coast. This process heats the ocean surface up and can alter the jet stream. The natural weather pattern can heighten the risk of severe storms, warmer summers, major snow events and even mudslides. Griggs says during El Nino years, southern California often gets more rain, but this year might be different.
GRIGGS: The consensus is now all of California is going to experience higher-than-normal rainfall.
ROMERO: Across the country, El Nino typically is a tale of two weather patterns, wetter in the southern U.S. and drier and hotter in the northern reaches of the country. Griggs says it's hard to say exactly how much human-caused climate change is boosting El Nino's strength, but it is altering oceans and global weather. And El Nino could worsen an existing marine heat wave along the West Coast, where temperatures have already risen by about 4 degrees.
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ROMERO: That worries Anita Giraldo Ospina. The marine scientists dove into Monterey Bay in early May to collect samples of kelp spores and urchin larva.
What was the temperature when you were down there? Did you check?
ANITA GIRALDO OSPINA: Yeah. Like 13 again.
ROMERO: That's right around 55 degrees Fahrenheit.
GIRALDO OSPINA: Feels warm for this time of year. It's definitely comfortable. (Laughter) Let's put it that way.
ROMERO: She says it's the seventh marine heat wave in seven years. And the combined influence of the already warm water and even warmer water from El Nino could disrupt ecosystems.
GIRALDO OSPINA: We are in such a, like, timely moment because we know what's coming with this marine heat wave, and at the same time, we're seeing all of this kelp starting to grow.
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ROMERO: But that water in the middle of the Pacific Ocean hasn't reached the West Coast yet, and scientists say that if it does, it just might intensify wet and dry weather across the country.
For NPR News, I'm Ezra David Romero.
(SOUNDBITE OF THE SIX PARTS SEVEN'S "SAVING WORDS FOR MAKING SENSE") Transcript provided by NPR, Copyright NPR.
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