the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 09 Jul 2026
Anthropogenic control on solar-induced hydro-meteorological summer extremes
Abstract. Solar variability leaves detectable, climate state–dependent imprints on summer hydro-meteorological extremes. We show that centennial-scale solar minima, including the Maunder and Dalton minima, enhanced summer flooding and heavy precipitation from Western to Southeastern Europe under pre-industrial conditions, by combining a chemistry–climate model with palaeoclimate reconstructions and proxy records. We identify the physical mechanism linking reduced solar irradiance, stratospheric ozone changes, and sea-ice persistence to modified meridional temperature and pressure gradients and a southward shift of the European storm track. Model–data convergence supports this mechanism and its intra-seasonal amplification toward late summer. In a high-emissions future climate, the loss of summer sea ice and a weaker, northward-shifted storm track suppress this pathway, diminishing the sensitivity of European summer extremes to identical solar perturbations. Our results highlight the critical role of background climate state for interpreting solar fingerprints in past records and assessing future risks.
Competing interests: G.L. is a member of the editorial board of Earth System Dynamics. All other authors do not have any potential conflicts of interest.
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
(13769 KB) - Metadata XML
- BibTeX
- EndNote
Status: open (until 30 Aug 2026)
- RC1: 'Comment on egusphere-2026-3630', Anonymous Referee #1, 03 Aug 2026 reply
Viewed
| HTML | XML | Total | BibTeX | EndNote | |
|---|---|---|---|---|---|
| 133 | 35 | 15 | 183 | 15 | 18 |
- HTML: 133
- PDF: 35
- XML: 15
- Total: 183
- BibTeX: 15
- EndNote: 18
Viewed (geographical distribution)
| Country | # | Views | % |
|---|
| Total: | 0 |
| HTML: | 0 |
| PDF: | 0 |
| XML: | 0 |
- 1
Summary: The manuscript explores the impact of a reduction of solar forcing on precipitation and precipitation extremes in Europe, in the preindustrial and under future anthropogenic climate change. The tools are simulations with atmosphere-ocean climate model that explicitly resolves the ozone photochemistry in the stratosphere.
The authors find that the impacts of a reduction in the solar constant, similar in magnitude to the Maunder and Dalton Grand Solar Minima, can increase the magnitude of precipitation extremes in Central Europe, but that this impact is much smaller in the future climate. The manuscript explores the transmission mechanisms, and it concludes that the reduction of sea ice in the future climate breaks the connection between changes in the solar forcing and precipitation extremes.
Recommendation: In my opinion, the manuscript and the study are well conducted, and I can recommend the publication of the manuscript after fairly modest revisions. One caveat of the study is that it is conducted with only one climate model, and thus the authors cannot assess the structural uncertainty. The conclusions remain therefore conditional on this climate model. Nevertheless, the study is interesting for follow-up experiments with other models
Main points
1) As I mentioned before, the main link in the mechanistic chain that links changes in solar forcing and precipitation and precipitation extremes is the sea-ice cover in the North Atlantic, which essentially modulates the meridional temperature gradients caused by changes in the solar forcing and absorption of radiation by ozone. While this is plausible, it seems to me a bit contradictory that the main response found by the study occurs in late boreal summer, precisely when the ice cover is at its minimum. Is this not contradictory with the main result, namely that the impacts in the future climate are diminished precisely because the ice cover is much reduced? Perhaps the seasonality of the atmospheric circulation is also important (?). In any case, this should be mentioned and ideally discussed, as it is, apparently, a clear contradiction with the main hypothesis
Minor points
2) The description of the model set-up is comprehensive, but a bit disorganised. For instance, when reading the methods section, I was initially led to believe that the model used was just an atmospheric model, and I was expecting a description of the source of the surface boundary conditions used in the simulations. Only hidden in one sentence, the authors mention that the climate model is coupled.
2) The acronyms TSI and SSI are not spelt out, unless I missed it
3) L 180: Slow-moving low-pressure systems can amplify these conditions, as during
the August 2005 flood.
Please specify which flood, where exactly, and if possible give a reference
4) L 184 Sediment records from the Ammer River, which is located in the Alpine foreland in southern Germany, reveal a clear anti-correlation between solar activity and flood frequency, particularly during pronounced GSM phases
The anticorrelation is relatively clear, but remains qualitative. This may be due to the strongly non-Gaussian behaviour of the SSN time series. For instance, between the two Grand Minima, TSI varies widely without the corresponding variations in flood frequency. Also, TSI was low during decades in the 19th century, and the flood frequency did not rise to the levels of the Maunder Minimum. During the Maunder Minimum itself, flood frequency also displays large variations, although SNN varied very little. Visually, it seems that the connection occurs at very long time scales, multidecadal or perhaps even centennial. I am aware that proxy reconstructions
are uncertain, but I would recommend toning down the 'clear correlation' and possibly discussing these caveats.
4) The conclusion section is, in my view, too long, and actually reads as a discussion. I would rename it to Discussion and add a Conclusions section with a few bullet points with the take-home message. Conclusions sections are very useful when the reader wants to just recall those messages.