This summer has been a scorcher for much of the Northern Hemisphere. June and July marked the hottest two-month stretch in Europe since record-keeping began. The contiguous US endured its hottest month on record in July. South Korea saw its highest-ever recorded temperature. The heat isn’t over yet, but some scientists are already looking ahead to 2027. Experts say the latest El Niño event is going to affect next year’s temperatures more than this year’s.So as the summer (slowly) starts to wane and temperatures (hopefully) start to come down, why has it been so hot this summer? What’s coming next year, and how should we prepare for it?As we burn fossil fuels and fill up the atmosphere with greenhouse gases, temperatures all over the globe are on the rise—climate change makes heat waves more likely and more intense. But different regions see different warming rates, and Europe takes the prize for the world’s fastest-warming continent. (It’s second only to the Arctic in terms of regional warming.)So it’s not terribly surprising that Europe has seen a particularly brutal summer, battered with heat wave after heat wave. One study looked at the continent’s May heat wave and found that climate change played a major role: A similar heat wave in 1976 would have been about 3.5 °C (6.3 °F) cooler than it was under today’s conditions.The US hasn’t been excused from the heat either. July’s record for the contiguous US (which excludes Alaska and Hawaii) officially ends one held by July 1936 for nearly a century. It’s concerning that we’re breaking records set during the Dust Bowl, an environmental disaster across much of the country.But looking ahead to next year, El Niño could have even more in store.A quick crash course here: There’s a natural variation in patterns across the oceans and atmosphere called the El Niño–Southern Oscillation, or ENSO. Basically, over the course of several years, feedback systems between the ocean and wind patterns shift one way and then another. (These two states are the El Niño and La Niña events.)The Pacific Ocean gets a lot of sunlight, warming up the water’s surface. In normal conditions the trade winds, caused by Earth’s rotation, carry that warm water west, forcing colder water deep in the ocean up toward the surface in the east. In turn, warm air rises, flows east, and sinks again.During an El Niño, the trade winds weaken and heat stored in the central Pacific builds up, warming up the air above it and creating a pocket of air that disrupts movement in the atmosphere and oceans, altering rainfall and weather across the globe.We’ve already entered an El Niño phase, defined by the National Oceanic and Atmospheric Administration as a period when we see the temperature in a specific part of the Pacific Ocean get 0.5 °C hotter than usual, plus associated changes in the atmosphere.And this could be a big deal for global temperatures. El Niño doesn’t actually add energy into the climate system or warm up the entire globe on a long-term scale. It’s essentially just taking heat that’s been stored in the oceans and releasing it into the atmosphere. But climate change has pushed a lot of heat into storage in the atmosphere and oceans—so combining the effects of this year-to-year variation with that long-term trend could have brutal results.This El Niño is expected to be an especially notable one. Some forecasts predict that the event could peak at over 3.5 °C above the average, potentially making it the strongest on record. It also came on quite quickly, representing “one of the fastest onsets in the observational record,” writes climate scientist Zeke Hausfather in an analysis for Carbon Brief.And while this El Niño is already starting to have an effect on temperatures, it’s still ramping up. El Niño’s effect on global temperatures tends to lag development of the ocean pattern by several months, and the effects will likely be more significant next year. In some recent El Niño periods, record-breaking temperatures came during the second calendar year of the event, Hausfather points out in his analysis. The most recent El Niño developed in 2023 and ran into 2024, and 2024 is the reigning hottest year on record. There’s some uncertainty in trying to predict how the rest of this El Niño will play out, but so far, it is set to be a doozy.Given how brutal these summer heat waves have been, there’s a pretty high likelihood that much of the world could see even higher temperatures next year. “El Niño conditions will pour fuel on the fire of a warming world,” United Nations Secretary-General António Guterres said in a video statement in June.It’s time to start preparing for it, and individuals can take some actions in the near term: If you’ve been putting it off, I’d buy that air conditioner, install solar and a backup battery, or upgrade the insulation in your home. In the longer term, though, temperatures will keep climbing because we’re still burning fossil fuels and driving climate change. As Guterres said in his statement, “The only effective response is climate action equal to the crisis: ending the addiction to fossil fuels, accelerating the shift to renewables, protecting the most vulnerable, and delivering early warning systems for all.”This article is from The Spark, MIT Technology Review’s weekly climate newsletter. To receive it in your inbox every Wednesday, sign up here.