Did we surpass 1.5 C of warming in 2024? It depends on who you ask
Overall, the message is the same: Earth continues to warm, resulting in dangerous climate disasters
Today, six climate agencies from around the world all confirmed what we knew was coming: Earth once again experienced its hottest year on record.
But whether or not it surpassed 1.5 C above the pre-industrial average depends on which climate agency you look at.
According to the EU's Copernicus Climate Change Service, 2024 was the warmest year on record dating back to 1850, coming in at 1.6 C above the pre-industrial average (1850-1900). It beat out 2023 as the hottest year on record, which was 1.48 C warmer than the pre-industrial average.
However, according to NASA, 2024 was 1.47 C warmer than the pre-industrial average, hovering ever so close to 1.5 C.
The National Oceanic and Atmospheric Administration (NOAA) found that it was 1.46 C warmer.
Berkeley Earth, a non-profit climate analysis organization, also found that 2024 was 1.62 C warmer than the pre-industrial average.
The numbers vary among the agencies due to the way the climate agencies gather past data.
However, the World Meteorological Organization looked at all these analyses, plus those from the U.K.'s Met Office and Japanese Meteorological Agency, and found that we "likely" passed 1.5 C of warming in 2024.
But what is agreed upon is that the past 10 years have been the warmest on record.
Though this may be the first calendar year to surpass the 1.5 C threshold set out in the Paris Agreement, it doesn't mean that we've broken that agreement. That threshold — the pledge from 195 countries to keep global warming below 1.5 C of the pre-industrial average — applies to many years where Earth's temperature is consistently above that, not just one or two.
And it also doesn't mean there's no hope to keep warming from going beyond that goal. As climate scientists often say, "every fraction of a degree matters."
This isn't the first 12-month period of warming above that threshold. From mid-2023 to mid-2024, the planet was 1.5 C warmer. It's just that it didn't happen over a calendar year.
Does 1.5 really matter?
While there may be some disagreement as to the exact degree of warming — in just the hundredths of a degree — the message is the same: Earth keeps getting warmer.
"What we can say, I think, is that it's likely that 2024 breached the 1.5 limit," said Gavin Schmidt, director of NASA's Goddard Institute for Space Studies. "However, the impacts that we're seeing, if it's like 1.48 or 1.52 or 1.6 you know, they're pretty much the same."
"We're seeing that increased intensity of rainfall, we're seeing the increased heat waves, we're seeing the rising sea level. All of those things don't really depend on the minor details of that last decimal point," said Schmidt.
According to World Weather Attribution (WWA), climate-related disasters contributed to the deaths of at least 3,700 people and the displacement of millions in the 26 weather events they studied in 2024.
In their December report, WWA noted that, "These were just a small fraction of the 219 events that met our trigger criteria, used to identify the most impactful weather events. It's likely the total number of people killed in extreme weather events intensified by climate change this year is in the tens, or hundreds of thousands."
When will we know we've passed the Paris Agreement threshold?
While 2024 started with high temperatures, fuelled by an El Niño — a natural, cyclical warming in a region of the Pacific Ocean that, coupled with the atmosphere, can cause global temperatures to rise — that's not the case for 2025.
"This year, 2025, we're starting with a kind of mild landing year, a little bit on the cool side," Schmidt said. "So that's going to be the contrast between 2025 and 2024: we're starting off on a cooler level. So we expect 2025 to be cooler than 2024 but perhaps not by very much."
Instead of an El Niño, we're starting off with a La Niña advisory, which can bring global temperatures a little lower.
Even if 2025 brings a cooler year, the trend is that Earth's temperature is moving steadily upwards.
But knowing when we pass the 1.5 C threshold of the Paris Agreement is tricky.
"It's generally been interpreted, including the most recent [Intergovernmental Panel on Climate Change] report, is that pre-industrial means 1850 to 1900, and passing the target means that the average of a 20-year period past 1.5 degrees," said Zeke Hausfather, a research scientist at Berkeley Earth.
"The problem with that definition, of course, is that we won't actually know when we passed 1.5 degrees until 10 years after we passed 1.5 degrees, which is not a very useful definition," he said.
But Hausfather noted that there are climate scientists trying to come up with a better way of making that determination sooner.
Still, he said, "We're probably going to firmly pass 1.5 degrees in the next five to 10 years."
And while it may be tiresome to hear another year is for the record books no matter where it sits, Schmidt said there's a reason why.
"It's the same story every year or so, because the long-term trends are being driven by our emissions of fossil fuels, and they have not stopped," he said. "Until they stop, we're going to continue having the same conversation. And so, do I sound like a broken record? Yes, I do, because we keep breaking records."
For Hausfather, he, too, worries about the continuous upward temperature trend.
"Climate is an angry beast," he said. "We should stop poking it with sticks."
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