World’s hottest year: 2024 first to pass 1.5C warming limit

It wasn’t only air temperatures that set new marks in 2024. The world’s sea surface also reached a new daily high, while the total amount of moisture in the atmosphere reached record levels.

That the world is breaking new records is not a surprise: 2024 was always expected to be hot, because of the effect of the El Niño weather pattern – which ended around April last year – on top of human-caused warming.

But the margin of several records in recent years has been less expected, with some scientists fearing it could represent an acceleration of warming.

“I think it’s safe to say that both 2023 and 2024 temperatures surprised most climate scientists – we didn’t think we’d be seeing a year above 1.5C this early,” says Dr Hausfather.

“Since 2023 we’ve had around 0.2C of extra warming that we can’t fully explain, on top of what we had expected from climate change and El Niño,” agrees Helge Gößling, a climate physicist at the Alfred Wegener Institute in Germany

Various theories have been suggested to explain this ‘extra’ warmth, such as an apparent reduction in the low-level cloud cover that tends to cool the planet, and prolonged ocean heat following the end of El Niño.

“The question is whether this acceleration is something persistent linked to human activities that means we will have steeper warming in the future, or whether it is a part of natural variability,” Dr Gößling adds.

“At the moment it’s very hard to say.”

Despite this uncertainty, scientists stress that humans still have control over the future climate, and sharp reductions in emissions can lessen the consequences of warming.

“Even if 1.5 degrees is out the window, we still can probably limit warming to 1.6C, 1.7C or 1.8C this century,” says Dr Hausfather.

“That’s going to be far, far better than if we keep burning coal, oil and gas unabated and end up at 3C or 4C – it still really matters.”