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Wildfires have reached an unprecedented scale in the Northern Hemisphere. The summers of 2022 and 2023 demonstrated the destructive power of wildfires, especially in North America and southern Europe. Global warming leads to changes in fire danger. Specifically, fire seasons are assumed to become more extreme and will extend to more temperate regions in northern latitudes in the future. However, the extent to which the seasonality and severity of fire danger in regions of central Europe will change in the future remains to be investigated. Multiple studies claim that natural variability and model uncertainty hide the trend of increasing fire danger in multi-model climate simulations for future potentially fire-prone areas. Such a trend might be isolated with single-model initial-condition large ensembles (SMILEs), which help scientists to distinguish the forced response from natural variability. So far, the SMILE framework has only been applied for fire danger estimation on a global scale. To date, only a few dynamically downscaled regional SMILEs exist, although they enhance the spatial representation of climatic patterns on a regional or local scale. In this study, we use a regional SMILE of the Canadian Regional Climate Model version 5 Large Ensemble (CRCM5-LE) over a region in central Europe under the RCP8.5 (Representative Concentration Pathway) scenario from 1980 to 2099 to analyze changes in fire danger in an area that is currently not fire prone. We use the Canadian Forest Fire Weather Index (FWI) as a fire danger indicator. The study area covers four heterogeneous landscapes, namely the Alps, the Alpine Foreland, the lowlands of the South German Escarpment, and the Eastern Mountain Ranges of the Bavarian Forest. We demonstrate that the CRCM5-LE is a dataset suitable for disentangling climate trends from natural variability in a multi-variate fire danger metric. Our results show the strongest increases in the median (50th) and extreme (90th) quantiles of the FWI in the northern parts (South German Escarpment and Eastern Mountain Ranges) of the study area in the summer months of July and August. There, high fire danger becomes the median condition by the end of the century, and levels of high fire danger occur earlier in the fire season. The southern parts (Alps and Alpine Foreland) are less strongly affected by changes in fire danger than the northern parts. However, these regions reach their time of emergence (TOE) in the early 2040s because of very low current fire danger. In the northern parts, the climate change trend exceeds natural variability only in the late 2040s. We find that today's 100-year FWI event will occur every 30 years by 2050 and every 10 years by the end of the century. Our results highlight the potential for severe future fire events in central Europe, which is currently not very fire prone, and demonstrate the need for fire management even in regions with a temperate climate. [ABSTRACT FROM AUTHOR]

The present study analyses the climate change response of Alpine-Mediterranean heavy precipitation events (HPEs), often associated with hazardous flooding. We investigate HPE properties describing their propagation, scale and intensity, by applying a storm tracking algorithm in an ensemble of convection permitting regional climate models (cpRCMs) under the CMIP5-RCP85 forcing scenario. The climate change response of HPE properties we derive by comparing their mean values for periods nearfuture [2040, 2050] and farfuture [2090, 2100] against those of a present-day period historical [1996, 2005]. By the end of the 21st century the model ensemble projects the region's surface temperatures to increase by 4.0 ∘ C. In this warmer climate HPEs are found to propagate farther and faster. They last longer by 5%, their area increases by 15% and their precipitation volume by 35%. Their maximum precipitation rate increases by 13% and an estimate of severity is found increased by 20%. By differentiating specific HPE categories, regions and seasons we find that landfalling and orographically forced HPEs occurring in fall are most intense, heavy and severe. Most importantly we find that these events are also projected to respond most strongly to climate warming, meaning that they will be even more intense, heavy and severe. Consequently in Mediterranean regions the most dramatic changes must be expected, in particular in Southern Italy. But also in regions north of the Alps, where HPEs are generally weaker than to the south, HPEs are found to occur twice as often in wintertime accompanied with an increase in precipitation volume of about 50%. Our analysis also confirms that even though the Mediterranean climate is generally drier by the year 2100, precipitation amounts associated with HPEs are found to increase by 52%. Further HPEs are projected to be 12% more frequent overall, although their occurrence frequency decreases in summer. Eventually we show that the characteristic HPE properties scale with surface warming, meaning that the warmer the local climate is, the more frequent, intense, heavy and severe are HPEs. Notably statistical tests show that the ten-member cpRCM ensemble provides robust climate change responses of all HPE properties investigated. The projected changes of HPE properties infer an increase of flooding risk for communities of the Alpine-Mediterranean area and thus the results presented here may encourage local authorities in adapting their flood protection measurements to climate change. [ABSTRACT FROM AUTHOR]

Very small glaciers (<0.5 km2) account for more than 80% of the total number of glaciers and more than 15% of the total glacier area in the European Alps. This study seeks to better understand the impact of extreme snowfall events on the resilience of very small glaciers and ice patches in the southeastern European Alps, an area with the highest mean annual precipitation in the entire Alpine chain. Mean annual precipitation here is up to 3300 mm water equivalent, and the winter snow accumulation is approximately 6.80 m at 1800 m asl averaged over the period 1979–2018. As a consequence, very small glaciers and ice/firn patches are still present in this area at rather low altitudes (1830–2340 m). We performed repeated geodetic mass balance measurements on 14 ice bodies during the period 2006–2018 and the results show an increase greater than 10% increase in ice volume over this period. This is in accordance with several extreme winter snow accumulations in the 2000s, promoting a positive mass balance in the following years. The long-term evolution of these very small glaciers and ice bodies matches well with changes in mean temperature of the ablation season linked to variability of Atlantic Multidecadal Oscillation. Nevertheless, the recent behaviour of such residual ice masses in this area where orographic precipitation represents an important component of weather amplification is somehow different to most of the Alps. We analysed synoptic meteorological conditions leading to the exceptional snowy winters in the 2000s, which appear to be related to the influence and modification of atmospheric planetary waves and Arctic Amplification, with further positive feedbacks due to change in local sea surface temperature and its interactions with low level flows and the orography. Although further summer warming is expected in the next decades, we conclude that modification of storm tracks and more frequent occurrence of extreme snowfall events during winter are crucial in ensuring the resilience of small glacial remnants in maritime alpine sectors. [ABSTRACT FROM AUTHOR]

The response of very small glaciers to climate changes is highly scattered and little known in comparison with larger ice bodies. In particular, small avalanche-fed and debris-covered glaciers lack mass balance series of sufficient length. In this paper we present 13 years of high-resolution observations over the Occidentale del Montasio Glacier, collected using Airborne Laser Scanning, Terrestrial Laser Scanning, and Structure from Motion Multi-View Stereo techniques for monitoring its geodetic mass balance and surface dynamics. The results have been analyzed jointly with meteorological variables, and compared to a sample of "reference" glaciers for the European Alps. From 2006 to 2019 the mass balance showed high interannual variability and an average rate much closer to zero than the average of the Alpine reference glaciers (−0.09 vs. −1.42 m water equivalent per year, respectively). This behavior can be explained by the high correlation between annual balance and solid precipitation, which displayed recent peaks. The air temperature is not significantly correlated with the mass balance, which is main controlled by avalanche activity, shadowing and debris cover. However, its rapid increase is progressively reducing the fraction of solid precipitation, and increasing the length of the ablation season. [ABSTRACT FROM AUTHOR]