Regional Climate Projections for British Columbia: Tools and Uncertainty

Adaptation to climate change requires planning and decision making at local and regional scales. Scenarios based on multiple projections from Global Climate Models may be used to indicate a range of future outcomes for a large region. However, demands are increasingly being placed on climate impacts scientists to produce information at higher spatial and temporal scales.

Each of three sources of information (GCMs, RCMs, and empirical downscaling) were analysed over the Province of British Columbia in order to obtain a comprehensive assessment of future projected changes to annual and seasonal temperature and precipitation for the 2050s compared with historical climate (1961-1990).

By the middle of the 21st century, BC-average anomalies from historical climate, based on an ensemble of 30 GCM projections run for the IPCC Fourth Assessment Report, are +1.7°C for annual temperature and +6% for annual precipitation. Winter and summer temperature anomalies are similar to annual. However, precipitation anomalies are +7% in winter and -3% in summer. The ensemble of projections was also used to determine a range of uncertainty surrounding these estimates, and to quantify the relative uncertainty attributable to GCM differences and to emissions scenarios.

BC is both a challenging and attractive locale for investigating high resolution projections because of the Pacific Ocean influence and effect of complex topography on regional climate. To compare with GCM results, single higher-resolution projections were obtained from the Canadian Regional Climate Model to illustrate the regional distribution of changes within the Province of BC. In addition, empirical downscaling using ClimateBC was used in order to compare to interpolated historical climatology.