Climate change attribution of Serbian summer heatwaves in 2024 and 2025

 The summers of 2024 and 2025 have been the hottest and the third hottest in Serbia since 1951, respectively. Analysis of observational data and results of regional climate models classify the whole southeastern Europe region as especially vulnerable and threatened by climate change. In light of this, we attempt to answer the question: Have these extremely hot summers been intensified as a consequence of climate change? To answer this, we have followed the World Weather Attribution protocol and methodology (Philip et al., 2020), using data from ERA5-Land reanalysis for the whole region of Serbia and regressing the extreme summer temperature events on 4-year smoothed global mean surface temperature, which is considered to be the indicator for global warming. The variable chosen to describe the heatwaves is the maximum of the multi-day running mean of daily maximum temperature (TX) averaged over Serbia. For the shorter, but more intensive 2025 heatwave, running mean was calculated over 3 days, and for the substantially longer 2024 heatwave, a 10-day averaging period was selected. The results are presented in conjunction with the more traditional heatwave percentile-based analysis using explorative statistics. Synthesis of results obtained from reanalysis data and EURO-CORDEX multi-model ensemble   has also been carried out to provide further confidence in the results. 

Results for the 2025 event suggest the country-wide three-day average maximum temperature value of 35.3℃ is 11.75 times more probable in current climate conditions than those in the mid-20th century, while synthesis of reanalysis and model results suggests that this number is around 5. The same comparison was done for the extreme event of 2024 suggesting the country-wide ten-day average maximum temperature value of 33.8℃ is 11 times more probable in current climate conditions. The probability ratio increases with the increase of the averaging period, up to 19.39 for a 20-day moving window, with the synthesized results following with slightly lower values.

The scientific results were further translated into public reports and policy briefs and communicated to policy and decision-makers to support climate-risk awareness and adaptation planning.This study was supported and funded by  the European Climate Fund (ECF).

References:

- Philip, S., Kew, S., Van Oldenborgh, G. J., Otto, F., Vautard, R., Van Der Wiel, K., King, A., Lott, F., Arrighi, J., Singh, R., and Van Aalst, M.: A protocol for probabilistic extreme event attribution analyses, Adv. Stat. Climatol. Meteorol. Oceanogr., 6, 177–203, https://doi.org/10.5194/ascmo-6-177-2020, 2020.