Climate Change Beat El Niño in Supercharging Record Hurricane Polo

A new joint study by the science teams World Weather Attribution and Climate Central, published Thursday, has split the blame for Hurricane Polo's record run between two culprits: human-caused climate change and a super El Niño. Global warming from the burning of coal, oil and gas added about six miles per hour to the storm's strength, while El Niño contributed slightly less, about five miles per hour, a study co-author told the Associated Press. The researchers had expected El Niño to play the larger role, given how extreme the current cycle is.

The attribution numbers tell a sharper story. According to the study, climate change made the ocean conditions that fueled the hurricane twenty-three times more likely, while El Niño made them fourteen times more likely. The two research groups measured conditions slightly differently and used different techniques, but reached the same general conclusion. That agreement gave the scientists more confidence in the result, although the rapid analysis has not yet been peer-reviewed.

Decoding Polo's rapid strengthening

Polo set the Pacific record for time spent at Category 5, holding the highest intensity for two-and-a-half days. The storm jumped from a tropical storm to a Category 5 with sustained winds of one hundred eighty miles per hour in about twenty-four hours. The fuel was ocean water at eighty-eight degrees Fahrenheit, as much as two degrees Celsius warmer than normal.

To calculate climate change's share, both teams compared what happened in the warmer real world to a hypothetical world that has not warmed by two-and-a-half degrees Fahrenheit, or one-point-four degrees Celsius, since pre-industrial times. The study found that without either climate change or El Niño, Polo would still have been a monster storm. But the scientists note that every bit of additional wind speed can dramatically increase the damage a storm inflicts.

How El Niño and climate change interact

The study also clarified how the two forces combine. El Niño usually increases storm-shredding high-altitude winds in the Atlantic. In the Pacific, wind pattern changes mean El Niño decreases the winds that weaken storms instead. Study co-author Daniel Gilford, a Climate Central scientist, compared the process to cars on a road: wind shear from El Niño can be a red light in the Atlantic or a green light in the Pacific, and the water warmed by both climate change and El Niño acts like a driver flooring the accelerator.

"El Niño and climate change both made this hurricane stronger than it would have otherwise been, but the effect of climate change is even bigger than the one of El Niño," said climate scientist and study co-author Friederike Otto, who coordinates the international science team behind World Weather Attribution. Otto added: "El Niño comes and goes, but climate change only gets worse. That means that now every hurricane that will occur in the East Pacific has at least this climate change signal making it stronger. And as long as we keep burning fossil fuels, that will only get bigger."

Why the finding may be conservative

Three outside scientists — Jeff Masters of Yale Climate Connections, the University of Pennsylvania's Michael Mann and North Carolina State University's Carl Schreck — told the Associated Press they believe the report understates how much climate change added to Polo's strength. Masters pointed to Gilford's own earlier research, which, as reported by the Associated Press, found climate change added sixteen miles per hour to hurricanes in the Atlantic between 2019 and 2023. Gilford acknowledged the new report could be underestimating climate change's impact, but said he was factoring in other conditions and being deliberately conservative.

University at Albany atmospheric scientist Brian Tang, who was not part of the study, said he was initially surprised climate change came out as the bigger influence, given how extreme this El Niño is. "But from a long-term standpoint, perhaps the result isn't as surprising as it might seem," he said.

Kristina Dahl, Climate Central's vice president for science, told the Associated Press the result is "a powerful reminder that even though El Niño right now is shifting hazards around the globe and changing where it's flooding and getting dry, the really dominant signal behind all of this remains climate change." Polo ultimately weakened considerably before reaching a sparsely populated part of Mexico's Baja California coast, but the researchers say the warning applies to every storm that forms in the East Pacific from here on.