# Quantifying the Occurrence of Multi-Hazards Due to Climate Change  
Diamando Vlachogiannis  
Environmental Research Laboratory (EREL), INRATES, NCSR \"Demokritos\", Agia Paraskevi, 15341 Attiki, Greece; [EMAIL_ADDRESS] (A.S.); [EMAIL_ADDRESS] (LM. ); [EMAIL_ADDRESS] (N.P. ); [EMAIL_ADDRESS] (S.K. ); [EMAIL_ADDRESS] (N.G.) [PERSON]  
Correspondence: [EMAIL_ADDRESS]; Tel. : +30-210-650-3417  
[PERSON]  
Department of Mathematics, University of California  
patterns of climate-change developments urge for more efficient risk management of climate-related extremes and disasters in order to significantly advance climate-change adaptation, particularly in the most vulnerable regions. This consequently implies the need for a reliable quantification of the probability of extremes in the current and future climate. Identifying the climate vulnerabilities of key societal systems should be based on a detailed knowledge of projected climate-change hazards and the factors affecting the likelihood of each one for the selected assessment of the region of interest. According to the report of the United Nations Office for Disaster Risk Reduction [32], the term \"multi-hazard\" is used to promote risk reduction and disaster management, and denotes hazardous events that may occur simultaneously or cumulatively over time. One of the most challenging research questions is the harmonization of risk metrics to allow the comparison of risks across hazards, regions, time, assets, or sectors [33]. Establishing a harmonized risk understanding would pave the way to a multi-hazard risk assessment, introducing interactions and cascading effects as well as providing some analytical interpretations of the compound and systemic risks. This would lead to more credible scenarios for describing future disaster events in terms of their magnitude and probability based on the validated scientific knowledge that can benefit from high-resolution climate projections. The single-hazard risk assessment is a proven methodology, but shifting to multi-hazards is not a linear or easily understood process, as a multi-hazard risk analysis is not just the sum of single hazard risk examinations and thus, comparability of the single-hazard results is strongly needed [34]. Due to the diversity of the hazard characteristics' complex relationships, triggering effects, climate-changing mechanisms, compounds and interactions could be potentially established [35; 36; 37]. In this work, the occurrence of hazards due to climate change was determined for Greece using data that were dynamically downscaled to a very high resolution by the Advanced Weather Research and Forecasting (WRF-ARW) model [38], initially produced by the EC-Earth Global Climate Model (GCM) [39]. The hindcast period covered the years from 1980 to 2004, while for the future projections, two different periods, i.e., 2025-2049 (near future) and 2075-2099 (far future), were studied using the Intergovernmental Panel on Climate Change (IPCC) Representative Concentration Pathways (RCPs), RCP4.5 and RCP8.5, following the recommendations of the EU National Risk Assessment [33] and similar studies in the US [40]. The RCP scenarios demonstrated a significant convergence in their emission pathways in the near future and considerable deviations towards the end of the century [41]. It has been established that high-resolution, dynamic-downscaling models applied to regional climate assessments can be implemented to assess the climate-change impacts on extremes, especially in areas with complex topography and local scale effects [42; 43; 44; 45]. Here, we sought to provide the first step towards a comprehensive multi-hazard risk assessment for the country based on high-resolution model data to support training and preparatory activities for disaster risk reduction (DRR). The analysis focused on four critical climate hazards for Europe: heat and cold extremes, flash floods, and windstorms, each one described by a climate indicator (Section 2.2).