Snow cover on Greek mountains has more than halved in four decades, study finds

“An international team of researchers, led by the University of Cambridge, used a combination of satellite imagery, climate data, terrain maps, and artificial intelligence to analyse how rising temperatures in the Mediterranean region have affected snow cover on the mountains of Greece – a region that is far less studied than other mountain ranges of Europe, such as the Alps or Pyrenees. Using the tool they developed, called snowMapper, the researchers found that snow cover has declined by 58% in the past forty years, and that the scale of decline has accelerated since the turn of the century. In addition, the snow season is both starting later and ending sooner. Their results, reported in the journal The Cryosphere , suggest that the loss of snow cover is driven by an increase in temperature, not a change in the amount of precipitation. Warmer air means that more precipitation falls as rain instead of snow at high altitudes, depriving downstream rivers of the ‘slow release’ water supply that snow provides. “Snow is like a natural reservoir,” said first author Konstantis Alexopoulos from Cambridge’s Scott Polar Research Institute (SPRI). “It’s sort of like putting money in your savings account versus spending it right away. If you store that money away for a while, it collects interest and is worth more when you need it. And because snow slowly melts instead of washing away like rain, it’s very valuable – for irrigation, hydropower generation, and household water needs – during the hot and dry summer months, as it keeps rivers, lakes, and groundwater topped up.” To quantify the degree of snow cover loss, the researchers used satellite imagery from NASA and ESA missions to show where snow was or wasn’t on clear days between 1984 and 2025. However, since cloud cover or shadows often obscure a clear view, the team used an AI technique called machine learning to help fill in the many gaps. They used European climate and digital terrain datasets to help simulate what snow cover was likely to have been on a given cloudy day, based on temperature, precipitation data, elevation, and whether snow was previously present. Their machine learning algorithm was trained on thousands of ground-based snow observations collected from weather stations across the Alps and Pyrenees. The result is a tool that provides daily, 100-metre resolution snow cover maps for ten of Greece’s highest massifs from 1984 to 2025. The researchers say that even though part of the data for snowMapper originated from elsewhere in Europe, the tool worked accurately in Greece, suggesting that snowMapper could be useful in other mountain ranges worldwide where data is sparse. “It’s vital to understand how snow processes are changing, yet most mountain ranges around the world don’t have much ground-based monitoring,” said Alexopoulos, who is also affiliated with the National Observatory of Athens and co-founder of the Hellenic Mountain Observatory. “Our model is here to solve that problem, since it can work accurately for regions without any local ground-based information at all.” The results showed that Greece is losing winter snow cover faster than most other mountain ranges, which could have serious implications for communities, agriculture and nature. The degree of observed snow loss and the rise in temperature fall outside the realm of normal climate variability. “Temperature controls how much of the precipitation will fall as snow rather than as rain, and how long-lived that snow will be once on the ground,” said co-author Professor Ian Willis, also from SPRI. “So as temperatures continue to rise, less snow will build up on the ground to begin with, and what does accumulate will melt faster too.” The loss of snow cover from the world’s mountains is another key indicator of how climate change is continuing to stress the natural world, especially in places like Greece, where watersheds are small, winter air temperatures are already close to zero degrees, and the melting snow helps protect against drought in the hot summer months. In future, the researchers are working to translate their results on snow cover into an analysis of volume changes in the water system, and project what could happen to water availability by the end of the century. The research team also included researchers from the British Antarctic Survey, the National Observatory of Athens and the Hellenic Mountain Observatory. The research was supported in part by the Bodossaki Foundation, the George & Marie Vergottis Foundation/Cambridge Trust and the Royal Geographical Society. Ian Willis is a Fellow of St Catharine’s College, Cambridge. Konstantis Alexopoulos is a Member of Girton College, Cambridge. Reference: Konstantis Alexopoulos et al. ‘Greek mountain snow cover halved in past four decades due to regional warming.’ The Cryopshere (2026). DOI: 10.5194/tc-20-2209-2026 Snow cover in the mountains of Greece – an important water source for communities, agriculture and natural ecosystems during the dry summer months – has more than halved over the past four decades, a study has found. Konstantis Alexopoulos / Hellenic Mountain Observatory Mount Grammos, Greece The text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License . Images, including our videos, are Copyright ©University of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – on our main website under its Terms and conditions , and on a range of channels including social media that permit your use and sharing of our content under their respective Terms. Yes

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