BetterIn January 2025, the World Meteorological Organization announced that 2024 had been the warmest year on record, at about 1.55 °C above pre-industrial levels.
Which produced a wave of headlines saying the 1.5 °C limit had been breached. In the same press release, the WMO wrote, in capitals, that this is not what it means.
The WMO: “passing the 1.5 °C threshold in a single year does NOT mean that we have failed to meet the long-term temperature goals of the Paris Agreement, which are measured over decades rather than any individual year.”
Long-term warming measured in 2024 is around 1.3 °C. And the goal, in the WMO's own words, is not out of reach but seriously compromised.
The textWhat the Paris Agreement actually says
The Agreement contains two numbers, and public conversation has kept only one of them.
Hold the global average temperature “well below 2 °C above pre-industrial levels” and pursue efforts “to limit the temperature increase to 1.5 °C above pre-industrial levels, recognizing that this would significantly reduce the risks and impacts of climate change”.
Two verbs, two ambitions. Hold below 2 °C is the commitment. Pursue efforts towards 1.5 °C is the aspiration. Neither of them is written as a date-stamped pass-or-fail test.
And the period is not defined. The WMO states it directly: the goal “refers to an extended period, typically decades or longer, although the Agreement itself does not provide a specific definition.” That absence is not a loophole, it is why the question “have we crossed it?” has no yes-or-no answer.
The year2024: 1.55 °C, and why that is not the crossing
So the measurement is real, and it is careful. The WMO calls 2024 “probably the first calendar year” in which the global mean temperature exceeded the 1850-1900 average by more than 1.5 °C.
Note the word probably, and note something the WMO adds and almost nobody repeats: not all six datasets place the anomaly above 1.5 °C, because their methodologies differ. All six do place 2024 first among the warmest years on record.
“It is important to emphasize that passing the 1.5 °C threshold in a single year does NOT mean that we have failed to meet the long-term temperature goals of the Paris Agreement, which are measured over decades rather than any individual year.”
The comparable figure1.3 °C: the other figure
If a single year is the wrong measurement, what is the right one? The WMO assembled an international team of experts specifically to answer that.
So two numbers coexist, and both are correct. 1.55 °C is what a single year did. 1.3 °C is where the underlying trend sits. The first makes headlines; the second is the one the Agreement is about.
The gap between them is not a discrepancy. It is what a single year of natural variability looks like on top of a trend.
The mental imageWhy it is not a cliff
The most damaging thing about the way 1.5 °C is discussed is not the confusion over measurement. It is the picture it puts in people's heads: a line, with safety on one side and catastrophe on the other.
The WMO Secretary-General: “it is essential to recognize that every fraction of a degree of warming matters. Whether it is at a level below or above 1.5 °C of warming, every additional increment of global warming increases the impacts on our lives, our economies and our planet.”
This cuts both ways, and that is why it matters. Below 1.5 °C, nothing is safe. Above it, nothing is lost. 1.6 is worse than 1.5, and better than 1.7and that sentence stays true at every value.
Which is why “it's too late” is the most expensive sentence in the conversation. If the threshold were a cliff, then passing it would end the argument. Because it is a gradient, passing it changes nothing about whether the next tenth of a degree is worth avoiding.
The other halfThe sentence not to forget
Everything above could be read as reassurance. It is not, and the WMO closes that door itself. One of its own headline points reads:
“The long-term temperature goal in the Paris Agreement has not become unreachable, but it is seriously compromised.”
And the WMO adds that, to help decision-makers, there is an urgent need for rigorous tracking, monitoring and communication of where warming stands relative to that long-term goal.
So the honest summary is uncomfortable in both directions. No, one year above 1.5 °C is not the crossing of the Paris threshold. Yes, the goal is in serious trouble. Anyone using the first half to drop the second is misreading the same press release.
QuestionsFrequently asked questions
Have we crossed the 1.5 °C threshold?
Not in the sense of the Paris Agreement. In 2024, the global average surface temperature was 1.55 °C above the 1850-1900 average, probably the first calendar year above 1.5 °C. But the WMO writes plainly that passing the threshold in a single year does NOT mean the Paris Agreement goals have failed, because they are measured over decades.
Over what period is the threshold measured, then?
The WMO answers: “an extended period, typically decades or longer, although the Agreement itself does not provide a specific definition”. That is an honest and uncomfortable answer, the exact duration is written nowhere in the treaty.
What is the actual level of warming today?
About 1.3 °C. The WMO set up an international team of experts whose first conclusion is that long-term global warming, as measured in 2024, is around 1.3 °C above the 1850-1900 baseline. It is that figure, not the 1.55 °C of a single year, that compares with the treaty's goal.
What exactly does the Paris Agreement say?
Two things, and only one gets remembered. It aims to hold the global average temperature “well below 2 °C above pre-industrial levels” and to pursue efforts “to limit the temperature increase to 1.5 °C”, recognizing that this would significantly reduce the risks and impacts of climate change.
If we go past it, is everything lost?
No, and the WMO says it twice. “Individual years pushing past the 1.5 degree limit do not mean the long-term goal is shot.” And: “Whether it is at a level below or above 1.5 °C of warming, every additional increment of global warming increases the impacts on our lives, economies and our planet.” In other words, it is not a cliff: every fraction of a degree matters, before and after.
Is the 1.55 °C figure certain?
It carries an uncertainty margin of ± 0.13 °C, and the WMO notes that all temperature assessments carry one. The figure is a consolidated average of six international datasets, and the WMO notes that not all of them place the anomaly above 1.5 °C, because of differing methodologies. All six do place 2024 as the warmest year on record.
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About this article. General and educational information. The figures quoted are from the World Meteorological Organization's consolidated analysis published on 10 January 2025, with their stated uncertainty: they are revised every year and will be again. This article describes what an institution measures and says, not a projection or a political position.
Spotted an error or an out-of-date figure? Write to us: we will correct it and re-date the article. Our texts are written with the help of artificial intelligence and checked against official sources before publication, but a figure or a definition can change without us catching it. If anything here does not match what an official body tells you, they are right.