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Warming of the Earth climate system is unequivocal. That climate changes affect the stability of natural and engineered slopes and have consequences on landslides, is also undisputable. Less clear is the type, extent, magnitude and direction of the changes in the stability conditions, and on the location, abundance, activity and frequency of landslides in response to the projected climate changes. Climate and landslides act at only partially overlapping spatial and temporal scales, complicating the evaluation of the climate impacts on landslides. We review the literature on landslide-climate studies, and find a bias in their geographical distribution, with large parts of the world not investigated. We recommend to fill the gap with new studies in Asia, South America, and Africa. We examine advantages and limits of the approaches adopted to evaluate the effects of climate variations on landslides, including prospective modelling and retrospective methods that use landslide and climate records. We consider changes in temperature, precipitation, wind and weather systems, and their direct and indirect effects on the stability of single slopes, and we use a probabilistic landslide hazard model to appraise regional landslide changes. Our review indicates that the modelling results of landslide-climate studies depend more on the emission scenarios, the Global Circulation Models, and the methods to downscale the climate variables, than on the description of the variables controlling slope processes. We advocate for constructing ensembles of projections based on a range of emissions scenarios, and to use carefully results from worst-case scenarios that may over/under-estimate landslide hazards and risk. We further advocate that uncertainties in the landslide projections must be quantified and communicated to decision makers and the public. We perform a preliminary global assessment of the future landslide impact, and we present a global map of the projected impact of climate change on landslide activity and abundance. Where global warming is expected to increase the frequency and intensity of severe rainfall events, a primary trigger of rapid-moving landslides that cause many landslide fatalities, we predict an increase in the number of people exposed to landslide risk. Finally, we give recommendations for landslide adaptation and risk reduction strategies in the framework of a warming climate.

Il documento illustra le attività svolte dall'Istituto di Ricerca per la Protezione Idrogeologica (IRPI), Centro di Competenza (CC) del Dipartimento della Protezione Civile (DPC), nell'ambito del progetto dal titolo "Valutazione integrata di dissesti geo-idrologici nel territorio della regione Puglia, modelli interpretativi dei fenomeni e definizione di soglie di pioggia per il possibile innesco di frane superficiali" per la Sezione Protezione Civile della Regione Puglia. In particolare, il documento è suddiviso in sei capitoli. Il Capitolo 1 contiene un'introduzione ai contenuti del documento. Il Capitolo 2 descrive il tool implementato dal CC CNR-IRPI per la ricostruzione degli eventi di pioggia e delle condizioni pluviometriche per l'innesco delle frane e la definizione oggettiva e riproducibile di soglie di pioggia empiriche a diverse probabilità di non superamento. Nel Capitolo 3 è descritta la rete pluviometrica regionale pugliese utilizzata per ricostruire gli eventi di pioggia presumibilmente responsabili dell'innesco dei fenomeni franosi. Nel Capitolo 4 viene descritto e analizzato il catalogo contenente le informazioni spaziali e temporali sui fenomeni franosi occorsi in Puglia. Il capitolo 5 mostra le condizioni pluviometriche responsabili dell'innesco dei fenomeni franosi e la definizione delle soglie pluviometriche empiriche per diverse probabilità di non superamento con le relative incertezze. Nello stesso capitolo viene mostrato il confronto tra la nuova soglia frequentista al 5% per la regione Puglia e le soglie precedentemente definite dal CC CNR-IRPI per altre regioni e per l'intero territorio nazionale. Il Capitolo 6 contiene l'elenco della bibliografia di riferimento.

Urbanization in hazardous regions, the abandonment of rural and mountain areas, and changed agricultural and forest practices have increased the impact of landslides through the years. Hence, the changing climate variables, like rainfall, acted and will act on a human-modified landscape. In this work, we analyze the role of rainfall variation and land use/cover change in the occurrence of landslides in Calabria in the period 1921-2010. Combining rainfall and landslide information, we reconstruct and analyze a catalogue of 1466 rainfall events with landslides (i.e., the occurrence of one or more landslide during or immediately after a rainfall event). To investigate the impact of land use/cover changes in the occurrence of landslides, we consider the "Land Use Map" made by the Italian National Research Council and the Italian Touring Club in 1956, and the "CORINE Land Cover" map released in 2000. Since our landslide catalogue is at municipality scale (i.e., for each landslide we known the municipality in which it occurred), we attribute a prevailing land use/cover class to each of the 409 municipalities of Calabria. We split the catalogue in two subsets (1921-1965 and 1966-2010) and correlate the landslides occurred in the first period to the 1956 land use and the landslides occurred in the second period to the 2000 land cover. We find that: (i) the geographical and the temporal distributions of rainfall-induced landslides have changed in the observation period; (ii) land use/cover in Calabria has changed between the two periods, with a huge decrease of arable land and an increase of heterogeneous agricultural areas and forests; (iii) in both periods, most of the landslides occurred in areas characterized by forests and arable land; (iv) in the second period, there was an increase (decrease) of landslides occurred in agricultural areas (arable land).

Changes in the main weather features are becoming perceivable in Italy. In the last years, the average temperature and the intensity of rainstorms are increasing. Such phenomena could lead to changes in the earth-atmosphere interaction. Accounting for the high vulnerability of the Italian territory, an obvious consequence would concern the effects on the hydro-geological hazards, including landslides and floods. As a matter of fact, the higher frequency of high magnitude flood and landslide events represent an alarm bell. It is necessary to explore with all available instruments the consequences of the potential climate changes. Since quantitative predictions are not possible, the only way to run is depicting rational scenarios for the most vulnerable contexts adopting a multidisciplinary approach. Based on projections of potential climate changes in the 21st century, the report examines their potential impact in the context of the Italian peninsula. After a general overview about typical slope responses to weather changes, some quantitative scenarios have been depicted for representative geomorphological contexts. The last part of the paper examines changes in the expected risk, based on the characteristics of the Italian territory and its vulnerability, looking at the initiatives to undertake for its mitigation.