Ice Cover on Lake Balaton in Western Hungary from 1885 to 2026
Reflections on Holocene Climate Variability with Reference to Historical and Contemporary Ice Formation on Central Europe’s Largest Inland Lake
Michael Hahl, Geographer
1. Introduction
The Little Ice Age (LIA), whose temporal extent is commonly dated in the scientific literature to approximately 1300–1850 or 1900, has traditionally been interpreted as the result of a combination of external forcings, in particular enhanced volcanic activity and reduced solar irradiance. However, this explanatory framework alone is insufficient to fully account for the observed rapid transition from the Medieval Warm Period into a multi-centennial cold phase.
In recent years, studies by Lapointe & Bradley (2021, 2025) in particular have opened up an alternative perspective: the climate system is understood as fundamentally non-linear, with the capacity for abrupt regime shifts driven explicitly by internal dynamics—specifically by ocean–atmosphere interactions and feedback mechanisms.
This shifts attention toward the question of inherent climate variability within the present warm period known as the Holocene.
The present contribution combines a paleoclimatic perspective with a regional observational level: the ice formation history of Lake Balaton in western Hungary.
The aim is to discuss regional ice phenology as an indicator of climatic variability, without attributing to it a causal role in large-scale climate processes. At the same time, the lack of linearity in Lake Balaton’s ice phenology over the period 1885–2026 is demonstrated. Implicitly, the data presented here—combined with current research on the onset of the Little Ice Age—highlight the significant role of fundamentally natural and partly abrupt climate variability.
Superimposed upon this natural variability, anthropogenic processes are also addressed, particularly the impacts of decades-long eutrophication in the Zala Hills and in Lake Balaton itself, as well as regional climatic effects associated with absent, unstable, or only partial ice cover.
From these considerations, a geo- and environmental-scientific as well as climate-geographical expansion of prevailing climate change models—incorporating criteria of natural climate variability alongside anthropogenic impacts at the geo-ecological level—can be critically and constructively derived.
2. Ice Phenology of Lake Balaton since 1885
Lake Balaton, very large but exceptionally shallow, with a length of 79 km, a maximum width of 14 km, an average depth of approximately 3 m, and a particularly shallow southern shoreline characterized by extensive littoral zones, is highly sensitive to changes in winter temperature and circulation conditions due to its continental winter climate.
A time series compiled by Hahl (2026) is based on the long-term dataset of Takács, Kern & Pásztor (2017/2018), supplemented by observations since 2018. It distinguishes between complete, closed ice cover and partial ice formation (shore zones, bays, ice fields).
Ice Formation on Lake Balaton in Western Hungary – 1885 to 2026
(Year – Ice cover: number of days with complete ice cover)
[Die tabellarische Jahresliste bleibt inhaltlich unverändert und wurde terminologisch direkt übersetzt; auf Wunsch kann ich sie auch in eine formale englische Tabelle (Journal-Format) überführen.]
Note on the term “partial”: This refers to spatially limited ice formation (shore zones, bays, shallow waters, ice fields, temporarily load-bearing sections) without a continuous, closed ice cover across the entire lake. It should be noted that in some years ice formation was confined to nearshore areas, whereas in others larger—but still partial—ice fields developed. Only years with a fully closed, load-bearing ice cover are classified here as “complete”. No specific information on ice thickness or stability is provided in this list.
In this analysis, the criterion of “closed ice cover” is proposed as an indicator of climatic development and variability. It must be relativized insofar as not only temperature but also wind conditions and wave activity determine whether complete ice formation occurs. A stable high-pressure meteorological situation is therefore an additional prerequisite.
3. Interpretation and Presentation of Explanatory Models
The datasets compiled by Hahl (2026) and, above all, by Takács, Kern & Pásztor (2017/2018) suggest the following interpretations.
3.1 No Linear Development since 1885
Since 1885—even after the gradual termination of the Little Ice Age—at least partial ice formation can be assumed for all winters due to the strongly continental climate. Repeated complete freeze-overs are well documented, in some cases of very long duration (e.g. 1894, 1946/47).
An accumulation of consecutive ice winters after 1885 can plausibly be interpreted as a late manifestation of the Little Ice Age. However, no linear trend is discernible; instead, pronounced interannual and decadal variability is evident.
3.2 Wind and Wave Action as Determinants of Ice Formation
In addition to temperature, wind conditions, wave action, and stable high-pressure systems are decisive controlling factors for the development of a closed ice cover. February 2022 may serve as an example: despite nighttime temperatures around −10 °C, no extensive ice cover developed, apparently due to prevailing wind conditions. Meteorological variables must therefore be incorporated into any detailed comparative analysis of ice phenology.
3.3 Interactions between Lake Ecology, Eutrophication, Ice Formation, and Regional Climate
Lake eutrophication can also contribute to delayed and shortened ice cover formation, a topic that warrants explicit treatment in climate-geographical and limnological studies—not only at Lake Balaton. At Balaton, eutrophication likely peaked in the 1980s and into the 1990s, before the construction and renaturation of the Kis-Balaton “forebay” system (especially Phase II, including the Fenéki Basin) and sediment dredging measures led, from the 1990s onward, to initial indications of a moderate return toward a more natural lake-ecological and ice-regime balance.
Of particular significance are two recent complete freeze-overs with multi-week ice cover (2017 and 2026). These years may already reflect a desired ecological optimization of the lake system, though it would be premature to give an all-clear. Further renaturation and floodplain reactivation measures along the Zala River, in the depressions of the Zala Hills, in the Kis-Balaton area, and at Lake Balaton itself remain strongly recommended (see also Hahl 2025).
In this context, it is also necessary to consider to what extent a lake that remained largely ice-free during winter months over several decades of strong eutrophication may itself have exerted a regional climatic influence. A closed ice cover on a 79 km long lake has a cooling and stabilizing effect on the surrounding regional climate. Conversely, largely ice-free winter conditions may further intensify eutrophication processes, constituting an additional feedback within the combined lake-ecological and climate-geographical system.
3.4 Natural Climate Variability and Ocean–Atmosphere Interactions
The present article does not confine its perspective to the geo-ecological level of human–environment interaction alone, but explicitly broadens the view to include abrupt climate variability within the Holocene context.
Contrary to the commonly simplified or distorted media narrative that the complete freezing of Lake Balaton in January 2026 represents a rare natural spectacle in times of anthropogenic climate change, an alternative and more complex perspective is discussed:
Can the strong ice formation observed at the “indicator” Lake Balaton, particularly in 2017 and 2026, be interpreted not as mere “meteorological outliers” within an assumed warming paradigm, nor solely as a result of lake-ecological interactions, but rather as early signals of abrupt climate variability—possibly even the onset of a cooling phase at a broader geographical scale, especially with regard to Central and Northeastern Europe?
Accordingly, the question of natural climate variability is explicitly foregrounded. To address it, a look at abrupt Holocene climate fluctuations is instructive, among which the Little Ice Age occupies a particularly prominent position. The current state of research on this topic can be drawn upon.
4. The Little Ice Age, Ocean–Atmosphere Interactions, and Abrupt Climate Variability
An increasing number of studies suggest that the onset of the multi-centennial cooling beginning around 1300—known in Holocene climate history as the Little Ice Age—can be explained, or must be explained, primarily by interactions and feedbacks within atmospheric and oceanic circulation systems.
4.1 Ocean–Atmosphere Circulation as the Primary Trigger of the Little Ice Age
Lapointe & Bradley (2021, 2025) reconstruct the onset of the Little Ice Age (ca. 1300–1850/1900) as an abrupt climate shift marked by strong cooling in the North Atlantic region.
The triggering processes identified include:
- an anomalously strong inflow of warm Atlantic water into the Nordic Seas
- enhanced ablation, detachment, and export of Arctic sea ice
- a resulting increase in freshwater input into the North Atlantic
- subsequent weakening of the Atlantic Meridional Overturning Circulation
⇒ abrupt climatic cooling (the “Little Ice Age” as a Holocene cold phase, ca. 1300–1850)
External factors such as volcanism or solar variability may modulate this process (cf. Berner et al. 2011; Miller et al. 2012), but are not necessarily required to trigger it. Similar lines of argument are advanced by other authors, including Alonso-García et al., Miles et al., and others (see references).
4.2 Climate-Geographical Process–Response System
The Little Ice Age thus appears as an expression of system-inherent climate variability. In this specific case, a climate-geographical process–response system includes atmospheric configurations, ocean currents, Arctic ice melt, rebound effects on ocean circulation, and—acting as a negative system feedback—climatic cooling. These interactions may be partly opposing, involving both amplifying and dampening feedback mechanisms.
5. Discussion: Scenarios of Climatic Variability
The linkage of analytical levels—paleoclimatic reconstruction using ocean–atmosphere models and regional ice phenology at Lake Balaton in Central Europe—does not permit prediction, but it does allow for the evaluation of possible scenarios and their integration into climate-geographical climate change research.
The present warm period, the Holocene, has never represented a stable climatic end state following glacial cooling, but rather forms part of a broader late-Pleistocene climatic dynamic characterized by recurring cold and warm phases.
A renewed clustering of regional ice winters—such as those observed at Lake Balaton—may indicate that abrupt and potentially persistent cold phases remain possible within the Holocene climate system. While such clusters are not necessarily equivalent to an ocean–atmosphere configuration like that which initiated the Little Ice Age, they nevertheless illustrate the fundamental capacity of the climate system for abrupt transitions.
The ice phenology of Lake Balaton in western Hungary can thus be regarded as a sensitive regional indicator of climate variability at least at the Central and Eastern European scale. The data from 1885 to 2026 demonstrate that no linear climatic development has occurred since the waning of the Little Ice Age, nor can such linearity be assumed today. Instead, significant variability is evident within the investigated time frame.
The works of Lapointe & Bradley and other authors, together with the Balaton ice phenology compiled by Takács, Kern & Pásztor (2017/2018) and Hahl (2026), converge on a common finding: abrupt cooling events and marked variability are intrinsic to the climate system. Even within the present warm period, such developments cannot be ruled out, as they are inherent to Pleistocene–Holocene climate history.
The Little Ice Age thus appears not as an exception within a Holocene warm phase, but as an expression of fundamental climate variability with the potential for system-internal self-regulation, involving both amplifying and dampening feedbacks. Regional observations such as ice formation on Lake Balaton may provide early indications of how such variability could manifest.
Anthropogenic factors—including eutrophication and its limiting effect on complete and stable ice formation over several decades, as well as regional climatic effects of absent ice cover—complement the picture of natural climate variability and must be integrated into further analyses of this climate-geographical process–response system.
The overly simplified media concept of an exclusively “man-made climate change” must therefore be critically reassessed with regard to both natural climate variability and anthropogenic geo-ecological impacts, as increasingly suggested by a wide range of research.
References
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Hahl, M. (2025). Umweltgeschichte und Gewässerökologie im Umfeld des Balatons. Entwässerung, Flussregulierung, Gewässerschutz und Renaturierung in den Senken des Zala-Hügellands, im Flusstal der Zala und am Plattensee in West-Ungarn (Environmental history and lake ecology in the Lake Balaton region: drainage, river regulation, water protection and renaturation in the depressions of the Zala Hills, the Zala River valley and Lake Balaton in western Hungary). ZALA LANDSCHAFTEN – Geoblog; ResearchGate.
Hahl, M. (2026). Vereisung des Balaton in Westungarn 1885–2026 (Ice formation on Lake Balaton in western Hungary, 1885–2026). ZALA LANDSCHAFTEN – Geoblog, Science channel (Telegram), 17 January 2026.
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Meteorological data sources:
Meteostat; NOAA Global Historical Climatology Network (GHCN).
Hungarian Meteorological Service (OMSZ).
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Translation: Hahl / ChatGPT
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Michael Hahl, German geographer, born in 1965 in Ludwigshafen am Rhein, holds a degree from the Department of Geography at Ruprecht Karl University of Heidelberg (Magister Artium in Geography, with Geology and Ethnology). He is the owner of the “Geographical Consulting Office proreg”, working on projects in regional geotourism, and serves as an expert and scientific consultant in the fields of geoecology, biogeography, habitat and species conservation, as well as issues of subsistence and human–environment interaction. He is a freelance author and founder of the ecophilosophical concept of “Consciousness Geography”. His research interests further include geomorphology, landscape genesis, climate history, geo- and environmental policy, among others. He is the author of more than 100 publications and expert reports in geoscience, geotourism, environmental history, and geoecology, as well as over 100 interpretive panel texts for geo-trails in nature and geoparks and visitor centers. He has conducted excursions to various regions of Eurasia, including the high mountain ranges of the Himalayas, the Scandinavian Mountains, and the Alps. His current geographical focus areas include western Hungary, southern Germany, and others. Further information, including an overview of publications, is available at www.proreg.de.
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