2025 was hotter than it should have been – 5 influences and a dirty surprise offer clues to what’s ahead

The past three years have been record hot, with 2025 seeing cooling factors like La Niña and fewer wildfires, despite overall global warming trends. Extreme weather continues to impact the planet.

The past three years have been the world’s hottest on record by far, with 2025 almost tied with 2023 for second place. With that energy came extreme weather, from flash flooding to powerful hurricanes and severe droughts. Yet, by most indicators, the planet should have been cooler in 2025 than it was.

So, what happened, and what does that say about the year ahead?

As an earth and environmental scientist, I study influences that affect global temperatures year to year, such as El Niño, wildfires and solar cycles. Some make Earth hotter. Some make it cooler. And one particularly unhealthy influence has been quietly hiding a large amount of global warming – until now.

The Earth’s climate is the result of many factors that change from year to year. Some that helped make 2025 cooler than 2024 include:

La Niña’s arrival: La Niña is part of the El Niño-Southern Oscillation, a natural climate pattern that fluctuates between warm El Niño conditions and cooler La Niña conditions. During El Niño, the Pacific Ocean heats up along the equator, influencing the atmosphere in ways that can cause intense storms, droughts and heat waves around the planet. La Niña does the opposite; it’s like putting an ice pack on the atmosphere.

Both 2023 and 2024 were El Niño years, but in 2025 conditions shifted to neutral and then to La Niña starting in September.

Fewer wildfires: Despite some destructive blazes, the world also saw fewer wildfires during 2025 than 2024, which put less carbon dioxide – a planet-warming greenhouse gas – into the atmosphere.

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