On 2–3 October 2020, a heavy precipitation event severely affected northern Italy and in particular the western Alps, with rainfall amount exceeding 600 mm over 24 h. This event was associated with an upper-level trough over the western Mediterranean basin, a large-scale configuration typical of heavy precipitation phenomena on the southern side of the Alps, since it induces a northward transport of large amounts of moisture impinging on the orography. The present study shows that a relevant amount of moisture moved towards the Mediterranean basin in the form of an atmospheric river (AR), a long and narrow filament-shaped structure crossing the whole Atlantic Ocean, characterized in the present case by a maximum Integrated Vapour Transport exceeding 1000 kg m−1 s−1. Therefore, in addition to the local contribution from the Mediterranean Sea, a relevant amount of moisture moved from the Tropics towards the Mediterranean, feeding the precipitation systems.The presence of an AR represented a distinguishing aspect of the event, superimposed on the well-known dynamic-thermodynamic mechanisms of heavy precipitation over the Alps. High-resolution numerical simulations and diagnostic tools have been exploited to investigate in detail how the transport of water vapour associated with the AR has influenced the dynamics and favoured the severity of the heavy precipitation processes.The results disclose the role of the AR and add further details to the theoretical framework of heavy precipitation mechanisms in the Alpine area, improving our understanding of the complex interaction between large-scale flows and mesoscale dynamics during extreme precipitation episodes. Due to the relatively fast evolution of the synoptic disturbance, the typical mesoscale mechanisms would have led only to an ordinary intense rainfall event. The contribution of the AR turned the event into a devastating flood.

Human-induced climate change and the resulting increase in severity and frequency of extreme weather events is a significant threat to cultural heritage. Those responsible for the care, maintenance and conservation of cultural heritage urgently need user-driven, site specific climate risk assessments. A risk assessment framework is developed: the Cultural Heritage Climate Risk Assessment (CHCRA). The CHCRA employs and combines high-resolution climate models, expert elicitation, and literature to estimate the expected damage to physical cultural heritage buildings from extreme events. As a pilot study, the CHCRA is applied to cultural heritage buildings in the Old and New Towns Edinburgh (ONTE), Scotland, which is part of the Edinburgh World Heritage Site. The UK Met Office UKCP18 2.2 km high-resolution climate model, regridded to 5 km, is used to analyse extreme 1-day rainfall events during 1981–2000, 2021–40 and 2061–80, driven by the RCP8.5 scenario. Simulated precipitation is combined with impact information to estimate expected damage per year. Autumn and summer expected damages are much larger than that from spring and winter. Expected damage per year, as percentage of rebuild cost, for autumn increases from 0.4% (5–95% CI: 0.2–0.6%) in the baseline period to 0.9% (0.6–1.2%) in 2021-40 and 1.2% (0.8–1.7%) in 2061-80. Summer sees a trend in expected damage per year increasing from 0.2% (0.09–0.15%) in the baseline period to 0.5% (0.3–0.8%) in 2021-40 and 1.0% (0.7–1.4%) in 2061-80. Combined annual expected damage per year increases from 0.6% (0.3–1.1%) in the baseline period to 1.5% (0.8–2.3%) in 2021-40 and 2.3% (1.4–3.3%) in 2061-80. A 3- to 4-fold increase in annual expected damage to cultural buildings in the ONTE is expected towards the end of the 21st century due to human-induced climate change.

Globally, the direct cost of natural disasters stands in the hundreds of billions of USD per year, at a time when water resources are under increasing stress and variability. Much of this burden rests on low- and middle-income countries that, despite their relative lack of wealth, exhibit considerable vulnerability such that losses measurably impact GDP. Within these countries, a growing middle class retains much of its wealth in property that may be increasingly exposed, while the few assets the poor may possess are often highly exposed. Vulnerability to extreme events is thus heterogeneous at both the global and subnational level. Moreover, the distribution and predictability of extreme events is also heterogeneous. Disaster managers and relief organizations are increasingly consulting operational climate information services as a way to mitigate the risks of extreme events, but appropriately targeting vulnerable communities remains a challenge. The advent of forecast-based anticipatory action has added to the suite of opportunities—and complexity—of operationalizing such services given varying prediction skill. Forecasts, including those at the subseasonal-to-seasonal (S2S) scale, may allow disaster managers to shift effort and therefore some risk from post-disaster response to pre-disaster preparedness; however, given the recent emergence of such programs, only a few, specific case studies have been evaluated. We therefore conduct a country-scale analysis pairing S2S forecast skill for monthly and seasonal lead times with flood and drought disaster risk to explore the potential for forecast-based anticipatory action programs broadly. To investigate subnational heterogeneity in risk and predictability, we also evaluate focused outcomes for the Greater Horn of Africa and Peru. Results suggest that forecast skill plays a large part in determining suitability for early action, and that skill itself varies considerably by disaster type, lead time, and location. Moreover, the physical and socioeconomic factors of risk can vary greatly between national and subnational levels, such that finer scale evaluations may considerably improve the effectiveness of early action protocols. By considering vulnerability at multiple spatial scales and forecast skill at multiple temporal scales, this analysis provides a first identification of promising locations for anticipatory action protocol development.

Quantitative and climatological analysis on the tracks and cyclogenesis locations of all 77 typhoons that hit Taiwan in the last 40 years (1977–2016) during typhoon season (May to November) is carried out. Ten pathways of all typhoons that hit Taiwan are detected with almost 1.9 typhoons per year. 53% of typhoons hit Taiwan from the East direction, typically (78%) only from the Philippine Sea. Typhoons from the West uniquely survive the longest hours with the highest sinuous tracks, often (59%) only from the South China Sea. Typhoons striking Taiwan from the East are the most intense whereas from the West the least intense. The Fisher's Exact and Chi-square (χ2) tests also establish that the sinuous nature of the tracks of typhoons is more responsible for the longer survival of typhoons (r = 0.67) than its strength. 26% more cyclogenesis is detected during the warm phase of El Niño Southern Oscillation (ENSO) than in the cold phase, which is also gradually rising in the last 4 decades. A 35% crucial growth in the strength of typhoons that hit Taiwan is observed by 0.4–0.7 °C rise in the Sea Surface Temperature (SST) in all four responsible oceans during the last 40 years (1977–2016). The role of the El-Niño epochs is found very crucial for the major SSTA changes during the typhoon season. The climatological analysis is fully consistent with statistical findings and leads to global warming as the major cause of the rising strength of typhoons that hit Taiwan during the study period.