Climatologists: Europe's May heatwave was exceptionally early
A ClimaMeter attribution analysis describes the conditions behind western Europe's May heatwave as rare and historically tied to autumn, linking them to human-caused climate change.
- An attribution analysis by the ClimaMeter group links western Europe's intense May heatwave to human-caused climate change.
- The conditions are described as rare and historically tied to autumn months rather than early May.
- According to the EU's Copernicus service, human activity had pushed warming to about 1.37 degrees by 2025.
- 2025 was confirmed as the third warmest year in the instrumental record.
The heatwave that struck western Europe in late May ranks among the most intense recorded so early in the year, according to an attribution analysis by the research group ClimaMeter. The authors describe the conditions behind that episode as rare and, by past experience, more typical of autumn than of the start of summer. The analysis attributes that signal to human-caused climate change rather than to random natural variability.
This is not an isolated finding. It fits into a longer series of measurements tracked by the EU’s Copernicus Climate Change Service. By those figures, human activity had pushed global warming to roughly 1.37 degrees above the pre-industrial level by 2025. Viewed through a decadal average, warming over the 2016 to 2025 period stands at about 1.26 degrees, a figure that smooths out year-to-year swings and shows the long-term trend more clearly.
Attribution science, the field ClimaMeter works in, does not claim that climate change “creates” any single heatwave. Instead, it compares how likely and how intense similar weather conditions are in today’s warmer atmosphere against the climate that existed before heavy fossil-fuel burning. When an early May spell turns out to be markedly rare by old standards yet more common in a warmer climate, that is the signal researchers attribute to human influence.
Why does the early date matter so much?
The timing here matters as much as the temperature itself. A heatwave in July or August fits the expected seasonal rhythm. A spell of similar intensity in May shifts the boundary of what counts as normal for that time of year. An early onset stretches the total window of heat exposure across the year, with consequences for agriculture, water supply and health, especially for the elderly and the chronically ill.
Most researchers who study the climate hold that shifts like these are not one-off exceptions but are becoming part of the new statistics. The context Copernicus provides supports that. 2025 was confirmed as the third warmest year in the instrumental record, which means extreme episodes now unfold against a background that is already warm. The same heat that would have sat at the edge of the record a few decades ago now fits an increasingly familiar pattern.
What this finding does not prove
It is worth drawing a clear line between what an attribution analysis shows and what it does not. It offers an estimate of likelihood and intensity, not absolute proof for every single hot day. The estimates rely on models and on comparison with historical data, so they carry the uncertainty the authors note. A rapid attribution study is, by the nature of the work, preliminary and open to later review and replication.
A single early heatwave, however pronounced, is also not the same thing as a long-term trend. A trend becomes visible only when many such episodes are observed across decades, and that is precisely where the ClimaMeter analysis leans on the broader Copernicus data on global warming. In other words, the individual event is linked to a changing climate, but it is not read as standalone proof of it.
For readers in Serbia and the wider region, where early springs and dry Mays are increasingly common, a practical question remains. Should early heatwaves be planned for as a regular part of the season, from irrigation to public-health measures, rather than treated as exceptions?
