The fingerprints on the fires in Chile and the floods in California: El Niño and warming

Two places known for what one scientist described as “benign Mediterranean climates” are being put to the test this week as an overheated climate and an El Niño weather cycle conspire to bring dangerous, record-breaking rainstorms to California and deadly fires in Chile .

Several counties in Central and Southern California were under a state of emergency Monday, with officials warning of life-threatening mudslides and possibly up to a year's worth of rain in just one day.

In Chile, President Gabriel Boric called for two days of national mourning and warned that the confirmed death toll, which is over 100, could “increase significantly” from the devastating fires.

Both the floods and fires in the Northern and Southern Hemispheres reflect the extreme weather risks caused by a dangerous cocktail of global warming, caused mainly by the burning of fossil fuels, and this year's El Niño, a cyclical weather phenomenon characterized by an overheated Pacific Ocean near the equator.

The disasters in Chile and California follow the hottest year on land and in the oceans. They announce what will almost certainly happen one of the five hottest years ago, according to the National Oceanic and Atmospheric Administration.

“These synchronized fires and floods in Chile and California are certainly a reminder of the extreme weather events and their consequences in otherwise favorable Mediterranean climates,” John Abatzoglou, a climate scientist at the University of California, Merced, said in an email. Climate variables, along with the effects of El Niño, are “the most important instruments in the orchestra for individual extreme events,” he said, “with the drum of climate change getting louder as the years go by.”

In the case of California, unusually high temperatures in the Pacific Ocean have increased atmospheric river storms that began Saturday and are expected to continue for at least another day. Parts of the Santa Monica Mountains received more than eight inches of rain this weekend, causing mudslides in some of Los Angeles' wealthiest neighborhoods.

Up to 14 centimeters of rain could fall in parts of the region on Monday, which would be close to annual average precipitation. City and state officials urged people to stay off the roads. The rain may peak around the time of the evening ride.

The two large-scale disasters highlight what some experts call an underappreciated danger of climate change. While a lot of money and attention has gone into preparing for California's drought, the likelihood of severe back-to-back storms also increases in a warming climate. “We're not really ready for this yet,” Daniel Swain, a climate scientist at the University of California, Los Angeles, said in a video he posted online Monday morning.

“We have failed to seriously consider the large plausible increase in flood risk in a warming climate,” he said.

Brett F. Sanders, an engineering professor at the University of California, Irvine, who focuses on flood control, said atmospheric river events like the ones now hitting the state have been predicted by climate models and pose new challenges for city planners.

“The mentality of the past was that we could control flooding and limit where flooding occurred. And beyond that, communities, businesses and residents could do what they do and not think about flooding,” said Dr. Sanders. “But we now know that across the U.S. we see infrastructure that is inadequate to manage today's extreme weather.”

Chile has suffered extreme fire conditions as a prolonged drought has dried up forests and depleted water supplies for much of the past decade. Last weekend there was a severe heat wave that also bore the traces of an El Niño period. During an El Niño, warmer-than-usual ocean temperatures in parts of the Pacific Ocean can influence climate patterns worldwide, increasing precipitation in some places and worsening drought elsewhere.

It didn't help that in Chile's heat- and drought-affected regions, there are large monoculture plantations of highly flammable trees close to towns and villages. When a fire broke out, high, hot winds spread the flames quickly. Aerial footage showed cars and houses burned to the ground in one of the country's most storied tourist destinations, in the Valparaiso region.

Chile is no stranger to fires during the hot summer months. An estimated 1.7 million hectares have burned in the past decade, three times the area burned in the previous decade. a recent study published in the journal Nature found that the “confluence of El Niño and climate-induced droughts and heat waves increases local fire risk and contributed decisively to the intense fire activity recently observed in central Chile.”

The government has increased funding for firefighting this year. It was insufficient to prevent the country's worst fires in a decade.

Sarah Feron, one of the authors of that study, saw it as a sign of things to come. “In some parts of the world we are facing climate-induced disasters that we are not prepared for and are unlikely to be able to fully adapt to,” she said.

Raymond Zhong reporting contributed.