Warming Skies Over Central Europe’s Mountains: Circulation Shifts Can’t Explain Rising Temperature Extremes

High in the mountains of Central Europe, the weather is changing in ways that scientists have now measured with unprecedented precision. A comprehensive new study published in Theoretical and Applied Climatology has tracked temperature extremes across ten mountain ranges in the Czech and Slovak Republics over a span of sixty-five years, from 1961 to 2025, and reached a conclusion that carries weight far beyond the region: the same atmospheric circulation patterns that once produced cold snaps now routinely deliver warm extremes, because the entire background climate in which those patterns operate has shifted. The research, led by David Tichopád of Masaryk University in Brno together with colleagues from the Czech Academy of Sciences and the Czech Hydrometeorological Institute, offers one of the most detailed decompositions yet of how circulation change and thermodynamic warming each contribute to the transformation of mountain climates.

The study area stretches roughly from 13 to 23 degrees east longitude and between 48 and 51 degrees north, encompassing an arc of mountains that begins with the Krušné hory and the Bohemian Forest in the west, passes through the Giant Mountains, Hrubý Jeseník and the Moravian-Silesian Beskids, and continues eastward across the Little and Great Fatra, the Low Tatras, the Tatras themselves and finally the East Slovak Mountains. All of the analysed terrain lies above 800 metres above sea level. The highest average elevation belongs to the Tatras at 1519.2 metres, while the Low Tatras cover the largest area at 1168 square kilometres. This west-to-east transect proved crucial, because it allowed the researchers to detect a striking spatial pattern in how quickly different ranges have warmed.

The data underpinning the analysis are formidable. Daily mean temperatures came from station measurements of the Czech and Slovak Hydrometeorological Institutes, which were subjected to rigorous quality control, homogenisation and gap-filling before being interpolated onto a 500 by 500 metre grid using regression kriging. Terrain variables such as altitude, slope orientation, roughness and convexity served as predictors, ensuring that the gridded temperatures reflected the complex topography of mountain landscapes. To characterise atmospheric circulation, the team turned to hourly geopotential height fields at the 850 hectopascal pressure level from the ERA5 reanalysis, aggregated into daily averages and classified into 27 distinct circulation types using an objective scheme based on flow strength, direction and vorticity.

The headline finding is unambiguous: every one of the ten mountain ranges has warmed significantly. Annual mean temperatures rose at rates between 0.28 degrees Celsius per decade in the Bohemian Forest and 0.44 degrees per decade in the East Slovak Mountains, with a pronounced west-east gradient in warming intensity. Seasonally, summer emerged as the fastest-warming season, with the Tatras recording 0.59 degrees per decade, while autumn showed the weakest trends. Comparing the periods 1961 to 1990 and 1991 to 2025, the difference in mean annual temperature ranged from 0.72 degrees in the Bohemian Forest to 1.36 degrees in the East Slovak Mountains, and a strong Spearman rank correlation of 0.85 confirmed that this eastward intensification of warming is statistically robust.

That longitudinal gradient is not an isolated curiosity. It aligns with broader evidence that northeastern Europe is warming faster than the southwest, and that inland and continental regions outpace coastal ones, a pattern the IPCC has documented at the global scale. The authors suggest that increasing thermal continentality may be at work, and that shifts in the position of cyclonic and anticyclonic dominance over Europe modulate the advection of maritime versus continental air masses. In practical terms, the mountains of eastern Slovakia are now living with a climate that is changing roughly twice as fast, in some measures, as that of their western Czech counterparts, with consequences for snow cover, growing seasons and the upper forest line that differ accordingly.

Circulation itself has not stood still. The classification revealed that anticyclonic types, the high-pressure regimes associated with sinking air, clear skies and persistent weather, have become more frequent, while cyclonic types have declined, particularly during spring and summer. Anticyclonic circulation increased significantly by 5.93 percent in winter and 4.81 percent in summer, driven largely by the AW type in winter and the A and ASE types in summer. Cyclonic types fell by 6.41 percent in spring, with the CSE and CS types showing the largest decreases. This shift toward high-pressure dominance is consistent with documented changes in North Atlantic-European circulation, including altered blocking activity and jet-stream behaviour, and may reflect the poleward expansion of the subtropical circulation belt.

To define extremes, the researchers calculated daily temperature anomalies relative to the climatological mean for each calendar day, removing the seasonal cycle. Extremely warm days were those exceeding the 95th percentile of anomalies, extremely cold days those falling below the 5th percentile, with thresholds fixed separately for each mountain range and season. Between the two periods, extremely warm days increased by roughly 2 to 5 percent across all ranges, with the largest relative increases in the Great Fatra, Little Fatra and Low Tatras, while extremely cold days declined by about 1 to 3 percent, most sharply in the Little Fatra and East Slovak Mountains. Every one of these changes was statistically significant.

The most innovative part of the study is its decomposition framework. The probability of an extreme event was expressed as the sum, over all circulation types, of the frequency of each type multiplied by the conditional probability of an extreme given that type. Changes between the two periods were then split into a dynamic effect, arising from shifts in how often each circulation type occurs, and a thermodynamic effect, arising from changes in how warm a given type tends to be. The result was decisive: for both warm and cold extremes, and in nearly every season and mountain range, the within-type thermodynamic effect dominated. The same weather patterns that once brought cold days now bring fewer of them, and the same patterns that once brought occasional heat now deliver warm extremes far more often.

The physical mechanisms behind this thermodynamic dominance are well understood. Under anticyclonic conditions, especially during blocking events and persistent ridging, clear skies and enhanced radiative forcing favour the development of extremely warm days, while warm-air advection plays a secondary role. Over land, these conditions are amplified by soil-moisture deficits, as persistent anticyclones promote precipitation shortfalls and enhanced evapotranspiration, further heating the surface. In winter and spring, the decline in extremely cold days has been linked to warming within anticyclonic and easterly types, plausibly connected to shrinking snow cover, where the snow-albedo feedback accelerates near-surface warming. Meanwhile, the significant summer increase in anticyclonic frequency likely contributed to warm extremes, even if its overall contribution remained secondary to the thermodynamic signal.

For the mountains themselves, the stakes are high. These ranges harbour rich biodiversity vulnerable to heatwaves, and previous research has tied extreme warmth to high-mountain rockfall in the Alps and to shifts in vertical climatic belts in the Tatras. The new findings suggest that future changes in temperature extremes will depend not only on how circulation evolves, which remains deeply uncertain in climate projections, but on continued warming within existing circulation regimes. The message from sixty-five years of Central European mountain data is stark and viral in its simplicity: it is not primarily the weather map that has changed, but the climate within which the weather map plays out, and thermodynamic warming has now overtaken circulation change as the dominant driver of temperature extremes in these iconic landscapes.

Subject of Research: Influence of atmospheric circulation on temperature extremes in Central European mountain ranges from 1961 to 2025

Article Title: Influence of atmospheric circulation on temperature extremes in mountainous regions of Central Europe during 1961–2025

Article References: Tichopád, D., Řehoř, J., Dolák, L., Láska, K., Zahradníček, P., & Štěpánek, P. (2026). Influence of atmospheric circulation on temperature extremes in mountainous regions of Central Europe during 1961–2025. Theoretical and Applied Climatology, 157(11), Article 695. https://doi.org/10.1007/s00704-026-06605-0

Image Credits: AI Generated

DOI: 10.1007/s00704-026-06605-0

Keywords: atmospheric circulation, temperature extremes, Central Europe, mountain climate, climate change, anticyclonic circulation, ERA5 reanalysis, thermodynamic warming, Tatras, heatwaves, circulation types, warming trends