Extreme rainfall
Current climate projections indicate that extreme rainfall events will be more intense and frequent in the future. This trend will be even more significant with global warming.
While every climate model predicts there will be increases in extreme rainfall, the magnitude of these increases varies from one model to another. The increases also depend on the region, the duration of the rainfall events and how extreme they are. Thus, the most extreme short-duration rainfall events are likely to have the most marked increases.
Projections for southern Quebec
For southern Quebec, based on a high emissions scenario (SSP3-7.0), the projections show:
A 10% increase in annual 24-hour rainfall maxima for the 2041-2070 time horizon
An increase of around 15% to 20% for 2071-2100
These increases will be greater for annual maximum rainfall with a duration of less than 24 hours. They are expected to reach 15% for the period 2041-2070 and 20% to 25% for the period 2071-2100, based on the same emission scenario.
The complexity of obtaining reliable projections of short-duration extreme rainfall
The extent of the increase in the frequency of short-duration extreme rainfall events remains relatively uncertain. The representation of the processes that generate them in climate models is highly dependent on the models’ resolution. For global climate models, this representation is insufficient. Only regional models provide adequate information on this type of precipitation, but they don’t provide an explicit representation of stormy weather.
The increasing use of resolved convection in regional climate models improves the representation of certain processes associated with extreme rainfall, particularly summer rainfall. However, the cost in terms of computing time limits the production of simulations over long periods.
In the coming years, improvements in both climate projections and statistical adjustment methods (including methods using artificial intelligence) will result in upgraded products, which will support the implementation of more appropriate adaptation measures. That means the current projections for southern Quebec must be considered guideline values, to be adjusted as needed based on local risks.
