Scientists this week served up a classic climate horror sequel: El Niño is back, and it's brought its friend, decades of fossil fuel burning, along for the ride. The developing El Niño, they warned, will amplify heatwaves, droughts, and floods this year, but let's not forget the real star of the show - long-term warming from burning fossil fuels remains the main driver of climate extremes.
El Niño, for the uninitiated, is the warm phase of a semi-regular temperature oscillation in the tropical Pacific Ocean. During this phase, massive amounts of heat stored in the ocean get released into the atmosphere, temporarily raising the average annual global surface temperature by as much as 0.3 degrees Fahrenheit. Think of it as the climate system's version of a hot flash.
During an online briefing this week, researchers noted that the consequences of a moderate or strong El Niño today are more damaging than those of similar events just a few decades ago, because the entire global climate system is now substantially warmer. Fredi Otto, a professor in climate science at Imperial College London and a lead researcher with World Weather Attribution, put it bluntly: if the projected El Niño emerges on top of that warmer climate, there is a "serious risk of unprecedented weather extremes" that wouldn't have happened during similar historical El Niños.
El Niño conditions in 2015-2016 and 2023-2024 helped boost Earth's long-running fever to new records, and climatologists expect another spike in the months ahead. But Otto reminded everyone that the planet's temperature will keep reaching new record highs anyway, "because of human-induced climate change."
World Weather Attribution has assessed the effects of global warming on more than 100 extreme climate events since 2014. In almost every case, they found that "human-induced climate change has a much greater influence on the likelihood and intensity of extreme weather events" than El Niño cycles. One of their assessments showed that human-caused warming "far eclipsed" the effects of a strong El Niño on extreme rains in the Horn of Africa at the end of 2023.
Jemilah Mahmood, director of the Sunway Centre for Planetary Health at Sunway University in Indonesia, framed the stakes in terms of life and death, especially regarding extreme heat. "Heat is exactly the kind of crisis that our systems are designed to ignore until it's too late," Mahmood said. "It doesn't arrive with a named storm or a visible floodline. It kills quietly, in homes, in open fields, in the bodies of workers who have no choice but to be outside." She tallied grim statistics like the estimated 546,000 total annual heat-related global deaths, adding, "We have normalized a public health emergency by failing to name it as one. Those who contributed the least to this crisis are often those paying the highest health costs."
Hotspots at the confluence of El Niño-driven droughts and ongoing planetary heating are expected in wildfire-prone regions, including the Amazon, Canada, the western United States and Australia. Theodore Keeping, a wildfire researcher at the University of Reading in England, said firefighters in those regions are bracing for a severe year, potentially facing some of the most damaging fire conditions seen in recent history. He noted that the combination of El Niño on top of ongoing warming has driven a "whiplash" between extreme moisture and extreme drought, turning grasses and brush into combustible fuel.
This year, wildfires on several continents have already scorched an Alaska-sized area of land - more than half a million square miles - 50 percent more than average over the past 25 years. Almost all countries in West Africa and the Sahel region experienced record-breaking wildfires. But wildfire season is only beginning in many parts of the world, so with "this rapid start, in combination with the forecast El Niño … we're looking at a particularly severe year materializing," Keeping said.
Big fires that burned in "normally lusher regions" of East Asia, including Myanmar, Thailand and Laos, were associated with severe droughts linked to human-caused climate change. Keeping said that a strong El Niño "can have a major effect on wildfire risk" appearing later this year, increasing the likelihood of severe hot and dry conditions in Australia, the northwestern U.S. and Canada, and the Amazon rainforest.
Even if El Niño leads to "very extreme conditions later this year, it's not a reason to freak out," Otto said. "It comes and goes. Climate change, by contrast, gets worse and worse and worse as long as we do not stop burning fossil fuels. So climate change is the reason to freak out." A constructive response, she added, is within reach, "because we do know what to do about it. We have the knowledge and the technology to go very, very far away from using fossil fuels."