Required Reading: Climate Change Impacts in the Okanagan and BC

Anticipated Time Commitment: 20 Minutes

An evaluation of adaptation options must be based on the best possible understanding of the nature, magnitude, and speed of climate change. Climate scientists began developing computer simulations of the Earth’s climate in the 1960s and these models have become increasingly sophisticated and refined.

In the past decade, climate scientists have successfully downscaled global climate models to regional scales by taking into account the variability in temperature and precipitation introduced by topography.47 The Pacific Climate Impacts Consortium (PCIC) is a regional climate service center at the University of Victoria that provides practical information on the physical impacts of climate variability and change, in support of long-term planning.48 PCIC was a key partner in developing the regional adaptation strategies that preceded the Okanagan strategy and have assisted in the production of the agriculturally relevant regional climate projections for the 2020s and 2050s that are presented in this document.

Additional information about regional climate projections, maps, and related definitions may be found in Appendix B and Appendix C, and in PCIC’s Thompson-Okanagan climate summary at https://www.pacificclimate.org/sites/default/files/publications/Climate_Summary-Thompson-Okanagan.pdf

Figure 2: Okanagan Regional Climate Projections: 2020s to 2050s

Key climate projections for the Okanagan region in the 2020s to 2050s are summarized here. Projections were generated by PCIC using data available through their “Regional Analysis Tool.” Numbers provided are the median of all model runs (black line in the graphs), and the shaded area on the graphs shows the range of projected possible future conditions.

Temperature

Projections for key temperature variables show a strong increasing trend, with all models projecting warming in all seasons (see text box and Figure 2, previous page). This trend is significant compared to historical variability, and summer is projected to warm slightly more than other seasons.

Precipitation

While models show the possibility for both increasing and decreasing future annual precipitation, the median annual trend is an increase of 1.2% above the 1990 baseline by 2020 and increasing by 4.4% by 2050.

The majority of models show a decrease in summer precipitation. There may be a slight increase in the amount of winter precipitation, with a marked decrease in the amount falling as snow (see Figure 3).

The distribution of these temperature and precipitation changes is greatly influenced by local geographic settings — temperature by elevation, and precipitation by topography. As Figure 4 shows, temperatures are higher in the valley bottoms of the Okanagan region, with cooler temperatures and wetter conditions around the Okanagan range to the south and the Beaverdell Range to the east. Many agricultural operations in the Okanagan are located in valleys — or on the benches above — and would therefore be affected by the greater temperature increases.

Related Effects

The magnitude, frequency, and intensity of extreme events, for both temperature and rainfall, are also forecast to increase with climate change. Unusually warm temperatures are very likely to occur more often, and cold temperatures less frequently. Projections are for 2.2 times the number of summer “warm days” (days in June, July, and August that are warmer than the 90th percentile historic baseline Figure 3 Precipitation as Snow, 1970s to 2090s

Precipitation Projections

• Annual precipitation: +1.2% by 2020s (+4.4% by 2050s)
• Summer: −8% by 2020s (–9% by 2050s)
• Winter: +6% by 2020s (+9% by 2050s)
• Winter Snowfall: −9% decrease by 2020s (−19% by 2050s) temperature for that day) and 6.8 times the number of extremely hot days (days so hot they used to occur only once every 10 years).

The intensity and magnitude of extreme rainfall events are also projected to increase. Detailed projections for the 2050s may be found in the Extremes text box on the following page.

As precipitation in the Okanagan and in upstream areas changes, river systems in the region will likely shift to a more rain-dominated pattern, with less predictability and increased variability in timing and volume of flows. With changes to snowpack and temperatures, runoff peaks are likely to occur earlier in the season, with lower discharge later in the summer.

The projected changes outlined in this section will affect the Okanagan’s agricultural sector summarized in the next section.