Global reduction of snow cover in ski areas under climate change

S15 Fig. Southern Alps with ski areas and an underlying elevation layer (grey). Colouring indicates the percent change in annual snow cover days in each ski area in the future 2071– 2100 compared to historical (1981–2010) snow cover days under high emissions (SSP3-7.0) scenario. (TIF) S16 Fig. Rocky Mountains with ski areas and an underlying elevation layer (grey). Colour- ing indicates the percent change in annual snow cover days in each ski area in the future 2071–2100 compared to historical (1981–2010) snow cover days under high emissions (SSP3- 7.0) scenario. (TIF) S17 Fig. Historical and future annual snow cover days for all skiing areas combined and separated into low, medium and high population density. The figure is based on a very high (SSP5-8.5) emissions scenario. (TIF) S18 Fig. Historical and future annual snow cover days for all skiing areas combined and separated into low, medium and high population density. The figure is based on a low (SSP1-2.6) emissions scenario. (TIF) Acknowledgments We thank the Sport Ecology working group at the University of Bayreuth for their comments on the manuscript, which have improved the paper considerably and particularly Dr. Volker Audorff for his helpful ideas. Further, we acknowledge the data and GIS support from Dr. Dirk Karger from the Swiss Federal Research Institute WSL and the implementation of data quality control by Charlotte Mu¨ller from the University of Bayreuth. Author Contributions Conceptualization: Veronika Mitterwallner, Anna Walentowitz.

Formal analysis: Veronika Mitterwallner, Gregor Mathes, Anna Walentowitz. Methodology: Veronika Mitterwallner, Anna Walentowitz. Supervision: Manuel Steinbauer. Visualization: Veronika Mitterwallner, Gregor Mathes, Anna Walentowitz. Writing – original draft: Veronika Mitterwallner, Anna Walentowitz. Writing – review & editing: Veronika Mitterwallner, Manuel Steinbauer, Gregor Mathes, Anna Walentowitz. References 1. Hennessy K, Whetton P, Walsh K, Smith I, Bathols J, Hutchinson M, et al. Climate change effects on snow conditions in mainland Australia and adaptation at ski resorts through snowmaking. Clim Res. 2008; 35: 255–270. https://doi.org/10.3354/cr00706 2. Matiu M, Crespi A, Bertoldi G, Carmagnola CM, Marty C, Morin S, et al. Observed snow depth trends in the European Alps: 1971 to 2019. The Cryosphere. 2021; 15: 1343–1382. https://doi.org/10.5194/tc- 15-1343-2021 PLOS ONE Global reduction of snow cover in ski areas under climate change PLOS ONE | https://doi.org/10.1371/journal.pone.0299735 March 13, 2024 12 / 15