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It's looking almost certain that 2024 will be the hottest year on record. It's been so hot, it's even surprised scientists. Climate change is playing a big role, and humans could also be warming the climate in unexpected ways. Lauren Sommer of NPR's climate desk explains.
LAUREN SOMMER, BYLINE: Last year, 2023 was really hot. Average global temperatures took such a big jump, one scientist called it gobsmackingly bananas. But then came 2024, and scientists are repeating themselves.
JARED RENNIE: It's getting tiring saying over and over again that it's the warmest.
SOMMER: Jared Rennie, a research meteorologist at the National Oceanic and Atmospheric Administration, says records have been falling left and right.
RENNIE: It's the warmest year so far. It's the sixth warmest November in the U.S. It's the warmest autumn.
SOMMER: Rennie says it's looking almost 100% certain that 2024 will take over the top spot, becoming the hottest year since recordkeeping began in the mid-1800s. Some of the reasons why are clear. First, climate change. Burning fossil fuels is adding heat-trapping gases to the atmosphere. This year also started out with El Nino conditions. That's a natural pattern where the Pacific Ocean releases a lot of heat. But halfway through the year, El Nino faded, transitioning to La Nina, so scientists expected temperatures to drop.
RENNIE: Usually under La Nina conditions, we do tend to see not as warm. But we're still hitting records for not only the U.S. but all over the world, every continent, pretty much. And so that is surprising.
SOMMER: So scientists are looking for what could be causing that extra heat - basically, the sidekicks to climate change and El Nino. One factor could be an unexpected side effect of cleaning up pollution. Ships have started using cleaner fuel, leading to less air pollution. That means fewer tiny particles in the air, which can actually help form clouds. So less particles could mean less cloud cover, and that means more heat because clouds are like a shield blocking the sun's energy. It'll take time for scientists to sort out what role that played. But either way, Rennie says 2024 is part of a clear trend.
RENNIE: The last 10 years, I mean, most if not all of them are the Top 10. So we're all pretty much clustered - all the recent years are pretty much clustered as the warmest on record.
SOMMER: 2024 could be so warm, it may be the first year global temperatures pass a key threshold, 1.5 degrees Celsius. That's the level of warming that countries agreed to try to stay below. Though, technically, to truly miss that goal, the planet would have to hit that number for several years. Beyond that level of warming, scientists expect much bigger impacts. Kai Kornhuber is a climate scientist at the International Institute for Applied Systems Analysis, a research institute.
KAI KORNHUBER: One degree, 1.5 degrees, it doesn't seem so dramatic. But on a local scale, this can lead to, yeah, really dramatic record temperatures and extreme weather events.
SOMMER: Kornhuber recently did a study that found heat waves are getting worse much faster than predicted in some places, like Western Europe. The Earth's climate is complex, he says, so even a small amount of warming can lead to outsized impacts.
Lauren Sommer, NPR News.
(SOUNDBITE OF ARC DE SOLEIL'S "VOLUNTARY EXILE") Transcript provided by NPR, Copyright NPR.
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