Future projections of temperature changes in Ottawa, Canada through stepwise clustered downscaling of multiple GCMs under RCPs

As the capital city of Canada, Ottawa has been experiencing significant impacts of global climate change. How to adapt to future climate change is one of the biggest concerns in the city’s built and natural systems. It thus requires a comprehensive understanding of possible changes in the local climate of Ottawa, which can hardly be reflected in the coarse outputs of Global Climate Models (GCMs). Therefore, a stepwise clustered downscaling (SCD) model is employed in this study to help investigate the plausible changes in daily maximum, minimum, and mean temperatures in Ottawa. Outputs from multiple GCMs under the Representative Concentration Pathways (RCPs) are used as inputs to drive the SCD model in order to develop downscaled climate projections. The performance of SCD model is evaluated by comparing the model simulations to the observations (R2 > 0.87) over the historical periods. Future temperature projections and their likely temporal trends throughout this century are analyzed in detail to explore the regional variations of global warming in Ottawa, thus to provide scientific basis for developing appropriate adaptation strategies at different management levels. The results suggest that the City of Ottawa is likely to expect significant increasing trends in temperatures (i.e., 0.18–0.38 °C per decade in maximum temperature, 0.16–0.31 °C per decade in minimum temperature, and 0.17–0.34 °C per decade in mean temperature under RCP4.5; 0.46–0.54 °C per decade in maximum temperature, 0.37–0.45 °C per decade in minimum temperature, and 0.42–0.50 °C per decade in mean temperature under RCP8.5) throughout this century.