Regional climate risks from compound effects and their previsibility under climate change

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Our planet's climate system is on the margin of a major shift. According to the last Intergovernmental Panel on Climate Change assessment report, Canada will experience one of the strongest warmings in the world by the end of this century, in the context of a strong arctic amplification of warming. This is likely not only to modify the meteorological hazards and extremes, but also the duration, intensity and occurrence of precipitation (of all types), and the regime of winds and temperatures, especially in areas where warming will be most marked. Depending on future warming thresholds, it becomes increasingly crucial to assess the high-impact weather conditions that combine multivariate climate variables, because these are often associated with a higher risk, often with greater robustness or high probability, than those resulting from changes in the variables considered in isolation. In addition, assessments based on univariate statistics can significantly underestimate the risks associated with given extremes, especially if the impacts are the result of several dependent variables or moderate weather conditions that combine and generate extreme impacts at the regional or local scale. That's why, the previsibility of compound effects from concurrent extremes or meteorological hazards is needed, that include a better understanding and identification of key physical processes at fine scales, in order to reduce their negative impacts and to better prevent those events. The assessment of robust climate risk levels at the regional or local scale is currently lacking, mainly because the physical processes responsible for their occurrence are not well resolved in coarse scale climate models currently used in Canadian climate change research. This requires the use of very high-resolution weather and climate models (e.g., using "convection-permitting" models) to take into account the combination of local factors (e.g., topography, surface conditions, environmental features, etc.) and large-scale influences. In addition, the previsibility and assessment of hydrometeorological risks undoubtedly needs to be improved with oriented information based on their impacts. This Discovery Grant (DG) program will combine both regional climate model simulations at intermediate resolution (ex. 11 km) and very high resolution (e.g., convection-permitting < 3 km) to identify and evaluate the severity, duration and occurrence of atmospheric hazards and high impact weather conditions from compound effects. This will help to develop early warning systems with physically based and oriented impact approaches, and to be better prepare and to reduce consequences from a range of adverse weather and climate conditions under climate change. This DG research will also contribute to help stakeholders and governmental organizations to reinforce the resilience of organization, communities and individuals, considering the most plausible changes in atmospheric hazards.