El Niño Puts Earth in 'Uncharted Territory'

A powerful El Niño is building in the Pacific Ocean, and scientists say it could be one of the strongest ever recorded. At the same time, Earth's temperatures are already at historic highs because of climate change. Experts are now asking a big question: What happens when a record El Niño meets a record-warm planet? No one knows for sure, and that uncertainty has scientists both excited and concerned.

El Niño is a natural warming of ocean waters in the central and eastern Pacific Ocean. It shifts weather patterns around the world, bringing heavy rains to some places and droughts to others. Scientists have studied El Niño for decades, so they know a lot about what it usually does. But this time, the situation is different because the whole planet is much warmer than it used to be.

"We're in a bit of uncharted territory," said Ben Kirtman, a professor at the University of Miami's Rosenstiel School of Marine, Atmospheric, and Earth Science. He means that scientists are entering a situation they have never seen before. History may not be a useful guide this time. The combination of a powerful El Niño and a warming climate makes it hard to predict what will happen.

Over the past 50 years, only three El Niño events were called "extreme": 1982–83, 1997–98, and 2015–16. Scientists think this current El Niño could match or even beat those events. Michael McPhaden, a recently retired scientist from the National Oceanic and Atmospheric Administration (NOAA), said that El Niños today are different from those 40 years ago. That is because rising temperatures caused by greenhouse gases have changed the climate significantly.

Climate scientist Daniel Swain used a helpful comparison to explain the situation. He said that if El Niño brings us to the 8th or 9th floor of a building, global warming pushes us even higher — to the 10th or 11th floor. Every year in the decade since 2016 has ranked among Earth's ten warmest years ever recorded. Sea surface temperatures have been record-warm this year, and El Niño has not even reached its peak yet.

Scientists expect that a warmer atmosphere will make El Niño's effects more intense. Because warm air holds more moisture, storms could drop much heavier rainfall than usual. McPhaden explained that a region that normally gets heavy rain during El Niño could now experience extreme, flooding-level rain. At the same time, places that get droughts could suffer even worse dry spells, because warmer temperatures dry out soil and plants faster.

Some scientists, like Swain, believe that the southern United States and California have a strong chance of a much wetter-than-average winter. Others, like Kirtman, are less certain. Kirtman agrees that the usual El Niño weather patterns will likely show up, but he is not convinced those patterns will automatically be stronger just because El Niño is stronger. He says there is still much scientists do not fully understand.

Rather than seeing this as scary, some researchers think of it as a chance to learn. Emily Becker, a research professor at the Rosenstiel School, said this event will teach scientists things they have never known before. Kirtman added that studying this El Niño could show us what Earth's climate might look like 10 or 15 years from now. "More than anything, this is an opportunity to try to understand our future," Becker said.