El Niño watch issued as scientists eye imminent climate pattern shift

Already there are signs of that regime developing: Scientists said waters have warmed quickly off South America’s western coast, something that may “foreshadow changes across the Pacific basin,” the Weather Service said. Their confidence in a developing El Niño is increasing despite well-known limits to climate forecast accuracy at this time of year.

El Niño could arrive as early as next month, they said, with an estimated 62 percent chance it develops some time between May and July.

And conditions lead them to predict 40 percent chances that waters warm so significantly, an El Niño considered to be “strong” will develop by late in the year. The last time that happened, in 2016, global temperatures surged to record highs and helped trigger rainforest loss, coral bleaching, polar ice melt and wildfires.

El Niño is known for sending warmth and precipitation across the southern United States, triggering drought in parts of Australia, Indonesia and southern Africa, and limiting development of Atlantic hurricanes.

It also tends to accelerate long-term global warming trends. The warm Pacific waters tend to produce more cloud cover, which encourages more of the sun’s warmth to be trapped in the atmosphere. National Oceanic and Atmospheric Administration scientists have said that for every degree Celsius that El Niño warms surface waters in the central equatorial Pacific, the global average surface temperature rises by 0.07 degrees Celsius (0.13 degrees Fahrenheit) two to three months later.

The early signs of El Niño, in addition to warmer-than-expected global temperatures so far this year, have prompted some scientists to nudge upward their predictions of where 2023 could rank among Earth’s hottest years on record. In a monthly global temperature analysis posted Wednesday, Robert Rohde, lead scientist for Berkeley Earth, calculated “a substantial” 38 percent chance 2023 could set a record for global warmth.

The Weather Service’s climate forecast includes a 10 percent chance that El Niño fails to materialize by the end of the year, and that the planet remains under what are called “neutral” conditions, with neither El Niño nor La Niña. Without the influence of either regime, broader seasonal weather patterns can be especially difficult to predict.

La Niña, the cooler foil to El Niño, had been the dominant global climate pattern for the past three years, but it ended in February. Marked by cooler-than-normal Pacific waters, it contributed to drought in the Southwest United States and to active Atlantic hurricane seasons.