Environmental threat:

Waters off California are acidifying at an alarming rate, scientists report.

LOS ANGELES — Waters off the California coast are acidifying twice as fast as the global average, scientists found, threatening major fisheries and sounding the alarm that the ocean can absorb only so much more of the world’s carbon emissions.

A new study led by the National Oceanic and Atmospheric Administration also made an unexpected connection between acidification and a climate cycle known as the Pacific Decadal Oscillation — the same shifting forces that other scientists say have a played a big role in the higher and faster rates of sea level rise hitting California in recent years.

El Niño and La Niña cycles, researchers found, also add stress to these extreme changes in the ocean’s chemistry.

These findings come at a time when record amounts of emissions have already exacerbated the stress on the marine environment. When carbon dioxide mixes with seawater, it undergoes chemical reactions that increase the water’s acidity.

Across the globe, coral reefs are dying, oysters and clams are struggling to build their shells, and fish seem to be losing their sense of smell and direction. Harmful algal blooms are getting more toxic — and occurring more frequently.

Scientists call it the other major, but less talked about, CO2 problem.

The ocean covers more than 70% of the Earth’s surface and has long been the unsung hero of climate change. It has absorbed more than a quarter of the carbon dioxide released by humans since the Industrial Revolution, and about 90% of the resulting heat — helping the air we breathe at the expense of a souring sea.

Here in California’s coastal backyard, some of the nation’s most economically valuable fisheries are also the most vulnerable. Scientists for years have worried that the West

Coast would face some of the earliest, most severe changes in ocean carbon chemistry.

Many have noted how West Coast waters seemed to acidify faster, but there was little historical data to turn to. Ocean acidification has become a field of research only in recent decades, so information has been limited to what scientists have since started monitoring and discovering.