| 11 Jun 2026
Historical climate extremes in Europe and the connection between spring precipitation and summer heat
Abstract. Hot European summers are often preceded by dry springs such as in 2022, but also in 1473 or 1540, two well-known summers of catastrophic heat. Spring precipitation deficits deplete soil moisture levels, which can amplify extreme summer temperature anomalies in Europe through land-atmosphere feedback mechanisms and altered atmospheric circulation. However, the link is not particularly strong, and hence long time series might help to better elucidate the mechanisms. Starting from documentary data and an atlas of temperature, precipitation, and atmospheric circulation over Europe for climate extremes in the last 600 years, we explore this relationship in more detail. We analyse the extreme heat summer of 1473, which followed dry spring conditions in Southeastern Europe related to a positive East Atlantic pattern. We then use the ModE-RA paleo-reanalysis and combine it with an analysis of 11,760 years of atmospheric model simulations as well as other reanalyses and reconstructions. Using a moving climatology approach with LOESS regressions to calculate anomalies, we identify significant negative correlations between winter-spring precipitation and summer temperatures in all data sets in the latitude band 36°–48° N (strongest over southeastern Europe), corresponding to known moisture-limited regions. Moreover, apart from precipitation anomalies, hot summers are preceded by increased blocking over north-central Europe and a positive East Atlantic pattern. Conversely, dry winter-springs are followed by more frequent blocking over northern Europe and, in model simulations, an increase in frequency and intensity of summer heatwaves. A linear regression approach for temperature in the northern Mediterranean region shows that precipitation in April and May has a strong, direct influence that does not vanish when taking the detailed atmospheric circulation in winter, spring, and summer into account, and hence cannot be explained by the effect of circulation on both, spring precipitation and summer temperature.
This particularly fascinating article proposes to go back 600 years in the past of Europe in order to identify, using proxy and instrumental data, reanalyses, and numerical simulations, whether the combination of certain spring weather / climate conditions is, significantly, heralding hot summers (a terribly topical subject!).
Given the quality of this work, I have no negative criticism to make. I would just like to ask a few questions and propose some suggestions to the authors, which may possibly improve the understanding of certain points and results that seem particularly interesting to me.
1) Would it be possible to specify what is the influence of the climatic context of the Little Ice Age (and its more or less severe / attenuated internal oscillations) on the frequency of atmospheric circulation types and their manifestations in terms of weather conditions highlighted in this study?
- NAO+ and NAO- phases;
- blocking patterns;
- occurrence of megadrought events.
2) Climatic conditions (interannual variability and multi-year alternately warm / cool oscillations) and atmospheric circulation that occurred during the transition between the end of the Little Ice Age and the period of contemporary global warming, did they influence certain results?
3) Possibility of an influence of the type of data used and analyzed on the results?
Compared to proxy data, what impacts and what importance could have precisely the measurements carried out from the seventeenth century onwards and their development (increasingly numerous across Europe) over the following centuries, in the analyses and on the results obtained in this work?
4) Among the questions asked by the authors themselves about highlighting characteristics specific to South-Eastern Europe climatology in the interpretation and understanding of the results, maybe the classification of atmospheric circulation patterns used in this work is not precise enough? If the classification used is relevant at the scale of the European continent, it is probably less so at smaller scales. Would the use of a more detailed classification such as that of Hess-Brezowsky circulation types (Großwetterlagen), if possible in the context of this work, be better suited to this regional scale?