What’s behind this summer’s heat, and why 2027 could be worse

**Matt Honan** (0:00)
Welcome to MIT Technology Review Narrated. My name is Matt Honan. I'm our Editor-in-Chief.
Every week, we'll bring you a fascinating, new, in-depth story from the leading edge of science and technology, covering topics like AI, biotech, climate, energy, robotics, and more. Here's this week's story. I hope you enjoy it.

**SPEAKER_2** (0:22)
Narrated by Noa. Listen to more of the best articles from the world's biggest publishers on the Noa app, or at newsoveraudio.com.

**Martin Buchanan** (0:33)
Casey Crownhart writes, What's behind the summer's heat, and why 2027 could be worse?
This summer has been a scorcher for much of the Northern Hemisphere. June and July 2026 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 already looking ahead to 2027
Experts say the latest El Niño event is going to affect 2027's temperature more than 2026'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 2027, 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 Celsius, 6.3 Fahrenheit 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 2027, El Nino 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 Nino 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 Nino and La Nina 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 Nino, 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 Nino 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 Celsius hotter than usual, plus associated changes in the atmosphere. And this could be a big deal for global temperatures. El Nino 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 Nino is expected to be an especially notable one. Some forecasts predict that the event could peak at over 3.5 Celsius 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 Hausvater in an analysis for Carbon Brief. And while this El Nino is already starting to have an effect on temperatures, it's still ramping up. El Nino's effect on global temperatures tends to lag development of the ocean pattern by several months, and the effects will likely be more significant in 2027
In some recent El Nino periods, record-breaking temperatures came during the second calendar year of the event. Hausvater points out in his analysis. The most recent El Nino developed in 2023 and ran into 2024, and 2024 is the raining hottest year on record.