| 11 Jun 2026
Will there be more landslides and slushflows in Norway in a future climate?
Abstract. Norway is exposed to mass movement type of natural hazards, such as landslides and slushflows, due to its steep terrain, wet climate, and long winter season. Understanding how these hazards may evolve under future climate conditions is essential for land-use planning and design of protective measures, among others. This study provides the first nationwide, quantitative assessment of how climate change may affect the hazard of landslides and slushflows in Norway, using operational hydrometeorological threshold models coupled to high‑resolution climate and hydrological projections. These models are used to simulate daily landslide and slushflow hazard levels at 1×1 km resolution for both a reference period (1991–2020) and a future period (2071–2100) under a high greenhouse gas emission scenario. The results indicate a clear increase in landslide hazard across all regions of Norway. The frequency of moderate hazard levels (≥yellow) is projected to increase by 55–107 % depending on the region, mainly driven by increased water supply to the soil. In contrast, the response of slushflow hazard is strongly elevation‑dependent. At lower elevations, reduced snow depth and shorter snow seasons lead to a decrease in slushflow hazard (−54 to −68 % depending on the region), while at higher elevations more liquid water supply cause a marked increase (+138 to +159 % depending on the region). Future research should focus on improving observational datasets and better evaluating the performance of hydrometeorological threshold models.
The paper is of considerable interest. The extent of the analysis and the overall approach are valuable, as they attempt to fill a gap on a topic and for a continent for which only slightly more than fifty studies are currently available.
That said, the manuscript is clearly oriented towards the landslide component, and it would benefit from a substantial improvement of the part dealing with the atmospheric forcings that govern the process. In particular, more information is needed on the model chains employed, on the methods adopted, and above all on the analysis of the data, including a proper characterisation of the associated uncertainty. This would allow the results to be interpreted far more effectively.
Equally fundamental is an assessment of the reliability of the chain over the present climate (1991 to 2020), in order to establish whether the estimates are consistent with what would be obtained using observed data, or reanalysis and satellite products, which in any case act as a proxy of what actually occurred. I am aware that bias correction can resolve many of the biases in the estimates (CDF based), but its effect in terms of the underlying dynamics must always be considered and quantified.
Specific comments
"exposed to mass movement type of natural hazards": the intended meaning is not clear and should be rephrased.
"high greenhouse gas emission scenario": the reference should be to a concentration scenario rather than an emission scenario. Please amend this throughout the text.
Abstract: too many numbers are reported. General trends would be sufficient here.
L20: are there any references to catalogues, events, casualties or economic damages for Norway, so as to provide a minimum basis for comparability?
Since slushflows are relatively poorly known at the global scale, it would be useful to provide a concise definition, in a nutshell, for readers less familiar with this type of dynamics.
L45: the term "wetter" is questionable, since in many cases it is the precipitation patterns that change rather than the total accumulated amounts. The variation in seasonality will be pronounced, and over Norway the partitioning between rainfall and snowfall is a key discriminant.
L145: do you refer to cumulative values? This is quite interesting, since 7% corresponds to the same "magic number" associated with heavy rainfall events under a 1°C warming, as regulated by the Clausius Clapeyron relationship.
Figure 2: what is meant by "Water supply from the snowpack"?
L210: it should be emphasised that the use of a single scenario may lead to a considerable underestimation of the uncertainty. Moreover, it should be acknowledged, or at least stated, that while the equation "more severe implies warmer implies more critical" holds for all temperature related dynamics, the same may not be true for hydrology related processes, given the complexity of the systems involved.
Further details on the climate simulations are also essential. Simulations at 1 x 1 km resolution are rather rare, since they require substantial computational time and storage. I also understand that these represent a further downscaling of EURO-CORDEX, which is itself already a dynamical downscaling. The model chains should be reported explicitly (how many and which ones). The same applies to the bias correction, since the data are strongly influenced by the model adopted and by the way in which it is applied.
L311: when the 1991 to 2020 baseline is used, how are the years 2015 to 2020, which are not covered by the historical experiment, handled? Is SSP3-7.0 used directly?
L320: during the validation of the approach, it is important to establish whether the estimates produced by the model ensemble are consistent with those that would be obtained using observed precipitation and temperature values as input. Clearly this refers not to the day by day correspondence, but to the seasonality and to the climatological values.
Table 1: a measure of the uncertainty across the different simulations is essential, in addition to the single ensemble value.
Figure 5: please report in the legend the meaning of the colours as well.
Finally, this section also lacks any assessment of the inter model uncertainty, which is nevertheless crucial. Uncertainty estimates are introduced for some of the dynamics in the subsequent plots, but they should be incorporated into all the statistics from the outset. Otherwise, the reading and the overall usability of the manuscript become unnecessarily difficult.