Last month was the fourth hottest March globally on record, bringing with it warm ocean surface temperatures that likely signal the transition toward El Niño, according to a new report.
Copernicus Climate Change Service found that the average sea surface temperature for March was the second highest ever recorded for that month. The highest temperatures recorded was in 2024 during the last El Niño event.
“A transition from neutral to El Niño conditions is forecast by many climate centers for the second half of the year,” the service wrote.
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During El Niño, ocean surfaces warm, and surface winds weaken or switch directions. The warmer water tends to stay at the surface of the Pacific Ocean, which releases more heat into the atmosphere. Global temperatures typically increase during El Niño and fall during its counterpart, La Niña. During La Niña, ocean surfaces cool, and easterly winds along the equator become even stronger.
The National Oceanic and Atmospheric Administration on Thursday announced that La Niña conditions are over and that El Niño is expected to emerge at some point between May and July. It is forecast to last at least through the end of the year.
That means that the world isn’t currently in either El Niño or La Niña. Each event sees certain changes in both the ocean and the atmosphere.
Some forecasters are calling the upcoming event a “Super El Niño,” which happens when temperatures are more than 2 degrees Celsius above the average, though federal researchers at NOAA don’t use that term.
In the U.S., last month was the hottest March on record, NOAA announced on Wednesday.
Ten states recorded their warmest March on record: Arizona, California, Colorado, Idaho, Nevada, New Mexico, Oklahoma, Texas, Utah and Wyoming.
The last 12 months were the hottest yearlong span ever recorded for the continental U.S., according to NOAA. And above-average temperatures are predicted to continue for much of the U.S. in April.