Greenhouse gas emissions recorded since the adoption of the Paris Agreement in 2015 are believed to have contributed to making the heat wave that struck Europe in June 2025 more intense, according to a new study published in the scientific journal Geophysical Research Letters.
The researchers estimate there is a greater than 99% probability that the cumulative emissions over the past decade have increased the intensity of the heat episode. In some European regions, this contribution would have represented about one-third of a degree Celsius in the daily average temperature.
The study was led by Jared Trok of Stanford University, United States, and included the participation of Emily Gordon, a climate scientist at the University of Auckland. The investigation used a generative artificial intelligence model, known as a diffusion model, to separate the effects of different emission levels on extreme temperature events.
To train the model, the researchers used data simulated by ten global climate models, spanning the period from 1850 to 2100. From these data, the system learned to relate surface temperatures in Europe to different emission levels and to meteorological conditions such as atmospheric pressure and soil moisture.
“Even emissions since the Paris Agreement in 2015 have tangibly increased the magnitude of heat events,” says Emily Gordon, cited by the University of Auckland.
The researchers also found that the effect is not limited to the 2025 heat wave. According to the study, emissions over the last decade also contributed to raising the temperature during the warmest week recorded in Europe in each year since, at least, 2021.
The research seeks to advance a field of study that aims to determine more precisely the contribution of certain periods or sets of human emissions to extreme climate events. According to the researchers, this approach could also be relevant for climate-related legal processes, in which accountability for emissions is sought.
About one-fifth of all carbon dioxide emissions resulting from burning fossil fuels occurred in the decade following the adoption of the Paris Agreement. The agreement, approved in 2015 by nearly 200 countries, set the objective of limiting the increase in the global average temperature to well below 2 °C above pre-industrial levels, pursuing efforts to limit this increase to 1.5 °C.
