the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 12 Jun 2026
Past and future European atmospheric extreme events under climate change – the ClimXtreme program's structure and results
Abstract. The meteorological extreme events heatwaves, droughts, heavy precipitation, floods and wind storms affect socio-economic systems and generate considerable attention. The role of anthropogenic climate change in the generation, frequency, and severity of observed and future events triggers mitigation and adaptation questions. Weather-related extremes are rare and embedded into atmospheric dynamics. This sets the frame for a dynamical-statistical analysis coupled to detailed impact or risk studies of rare events. This approach is taken by the German Federal Ministry BMBFTR funded project ClimXtreme-1 with 35 sub-projects. Here we compile the contributions of 21 articles of the inter-journal NHESS/ASCMO/WCD special issue. We connect them to 33 peer reviewed ClimXtreme-1 writings in other journals. For archetypic events over continental areas in mid Europe the individual research results are reported. These involve the use of existing and newly developed indices, analyses of the atmospheric dynamics and process-based chains using global and regional climate models results and statistical detection and attribution studies, with emphasis on establishing a causal relationship between extreme events and anthropogenic climate change. Two overarching conclusions emerge from the joint appraisal of the ClimXtreme-1 publications. Firstly, conclusions on causality show that the attribution analyses of observed events demonstrate the necessary contribution of past anthropogenic climate change to the event while sufficient contributions to future extremes need to be established. Secondly, findings from the dynamic process studies highlight the need to expand the current attribution approaches (statistical vs. storyline) to include the mediator-moderator framework.
Competing interests: At least one of the (co-)authors is a member of the editorial board of Natural Hazards and Earth System Sciences.
Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.- Preprint
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Status: open (until 19 Sep 2026)
- RC1: 'Comment on egusphere-2026-2697', Anonymous Referee #1, 26 Aug 2026 reply
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- 1
This manuscript provides a broad overview of the ClimXtreme-1 program and synthesizes 21 papers from the inter-journal special issue together with 33 related peer-reviewed publications. It covers heatwaves and droughts, heavy precipitation and floods, wind storms, event attribution, impact studies, and the shared XCES infrastructure. The manuscript is potentially useful as a reference for readers interested in European weather extremes, and the attempt to connect process understanding with probabilistic and storyline attribution is interesting. However, although the paper tried to make several broad project-level and causal conclusions, the paper is poorly organized and it is more of a collection of individual research reports, without sufficient synthesis and summary. The basis of the synthesis, the scope of the review, and the reproducibility of the presented resources need to be explained more clearly. The following comments may help improve the manuscript.The paper should try to illustrate adequate innovation achievements briefly and seriously, as this is seemingly pan-European cooperation and your government surely support you a lot. Overall, this manuscript requires greatly major revisions before it is suitable for publication.
Major Concerns
--Try to improve the Introduction section carefully
The “1.1 Scientific Background” herein is not necessary, as the background of ClimateExtreme has been illustrated below. Please simplify or remove it.
Figure 1 should be removed or move to the supplementary file. Make no sense herein.
The “1.2 The ClimXtreme Project” is worthy of being introduced as much as possible, particular for perspectives and highlights. Therefore, I suggest this sub-section should be treated carefully, introduced briefly (as the whole paper illustrate them) and divided into several parts.
--section 2
Several sketch maps or workflow is important in this section rather than verbose paragraphs.
According to Line 114, “the process” in caption of section 2.1 is referred to as near-surface process. However, Line 14 in Abstract claimed the “dynamic process studies”, but throughout the paper, there are no enough evidence for conclusion of dynamic processes, therefore, please weaken it.
--section 2.4
Please list data bases including detailed information as specific as possible (user-friendly), rather than many literature reviews and Figure 2.
--Section 3: Transparency of the literature synthesis & Lack of research highlight
Section 3 states that the manuscript provides a comprehensive summary of 21 special-issue papers and 33 papers published elsewhere. However, as the section title is Hazard-specific research highlights, neither explicit and brief highlights, nor sufficient synthesis, are displayed. In addition, Lines 260-315 are redundant because each hazard has been illustrated below. Please simplify it.
Some indices in Table 1 are common sense rather than unique for the ClimateExtreme projects, please only list the newly proposed and robust indices in Table 1.Section 3.3 “3.3 Extratropical Cyclones” is not mentioned in Line 291.
--Geographic and hazard scope should be made consistent
The title refers to European atmospheric extremes, whereas many parts of the paper focus more narrowly on Germany or Central Europe. In addition, the introduction names four WCRP archetypes, including severe convective storms, but Section 3 is organized into three main hazard groups, with convective storms and floods included only within other sections. The heatwave and drought section also contains a detailed index table that has no parallel for heavy precipitation or wind storms. Please define the geographic and hazard scope at the beginning, explain the grouping choices, and use a more parallel structure across the hazard sections. If the available literature is uneven among hazards, this imbalance should be stated as a limitation of the synthesis.
Minor Issues
--Line 5: Check throughout the manuscript, use ClimXtreme-1 or ClimXtreme
--Number of conclusions and project outputs
The abstract says that two overarching conclusions emerge, whereas Section 4 presents three. The counts of 35 sub-projects, 54 research publications, two data publications, 21 special-issue papers, and 33 papers in other journals should also be checked and explained consistently.
--Presentation and definitions in Table 1
Table 1 would be clearer if it were reformatted as a standard three-line table, using only a top rule, a rule below the header, and a bottom rule, without vertical lines or excessive internal borders. Please also align the index names and references consistently and define abbreviated entries such as "n days" and "n events" more precisely. The full name of SPEI should be checked; it is normally written as the Standardized Precipitation Evapotranspiration Index. The table caption could specify whether the table is intended to be a complete inventory of ClimXtreme indices or only a selection.