Climate and Weather in British Columbia: Past, Present, and Future
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Pre-industrial Global Annual Average Temperature (GAAT) throughout the Holocene (the geological epoch spanning the past 12,000 years) varied by only a few tenths of a degree, producing an incredibly stable global climate. This stability allowed humanity to flourish, from a few million hunter gatherers and the invention of the wheel to over seven billion people and the development of incredible technologies such as reusable rockets.
However, Earth’s climate and weather has been, and is quickly changing, upending the stability humanity and the biosphere have relied upon for millennia. A recent paper indicates that GAAT today is warmer than at any point of the Holocene (1). Gradual warming over thousands of years (which is expected during interglacial periods) has been rapidly accelerating since the onset of the industrial revolution (see Article 1).
Humanity relies on a stable and predictable global climate and its associated weather patterns for food, shelter, recreation, and the functioning of our economies. Over the past decade, weather related events have triggered the displacement of an estimated 23 million people every year (2). Weather variability has immense impacts on our economies, with an average 3.4% variation in the United States annual economic activity alone, equating to $728.54 billion U.S. in 2019 GDP (3).
The biosphere has also become increasingly pressured due to anthropogenic climate change resulting in alterations to species genetics, physiology, and morphology, along with shifts in species distributions and alterations in the timing of seasonal patterns (e.g., migrations, flowering, mating, and more) (4). Disruptions to the biosphere as a result of climate change from scales of genes to entire ecosystems have had well documented impacts on people: from unpredictable crop yields and fishery landings, to biodiversity loss and the growing impacts of pests and diseases (4).
With global climate change comes alterations to the prevailing climate, and thus changes to the weather we can expect. These changes impact the biosphere along with the systems our society’s rely upon, from health care and food security to the cost of living (2). A greater understanding of climate and weather can help us to recognize our impact and role on this planet and be equipped with the knowledge to prepare for the future. This article will look at the primary factors determining the distribution of weather and climate in British Columbia (BC), how weather and climate have changed in BC, and how they are projected to change in the future.
Scales of weather and climate
Quick refresher: “weather” refers to the specific conditions of the atmosphere at a particular place and time; measured by variables such as wind speed & direction, air temperature, humidity, atmospheric pressure, cloudiness, and precipitation (5). These variables change from hour-to-hour, day-to-day, and season-to-season.
In contrast “climate” is the statistical characterization of weather over many years and is usually represented by means (averages), variability, and extremes of the aforementioned weather elements over rolling periods of thirty years updated each decade (known as a climate normal) (5).
The vast majority of weather is confined within a portion of the atmosphere known as the troposphere stretching from the earths surface to an average height of around 8-16 km (dependent on location, being thinnest at the poles and thickest at the equator) (6). Approximately 80% of the atmospheres mass and 99% of atmospheric water vapour is contained within the troposphere (this is why planes have an optimal cruising altitude of around 10 km in order to reduce air resistance and avoid the majority of Earth’s weather systems) (6).
Weather ranges across scales of both time and space, with the largest of these phenomena being planetary scale systems. These systems span tens of thousands of kilometers and exist from several days to several weeks and are heavily influenced by the latitudinal redistribution of energy and the Coriolis effect (7). Examples of planetary scale systems include semi-permanent pressure centres such as the Aleutian low (more on this later), the Polar vortices, and globe encircling upper air waves (such as the Westerlies and Trade winds) (7).
Figure 1: Idealized and actual Earth air waves and circulation cells. The net movement of energy is from the equator (where there is an energy surplus) to the poles (energy deficit) with the Coriolis effect determining the direction of the Trade Winds and Westerlies in each hemisphere. Image source.
Synoptic scale systems span a few hundred to several thousand kilometers and have lifetimes from a few to several days (7). This scale is especially important for day-to-day weather and includes air masses along with low pressure systems (extreme examples being cyclones which are differentiated as tropical cyclones [referred to regionally as hurricanes and typhoons] and extra-tropical cyclones [the predominant storm type experienced in BC]) and high pressure systems (anti-cyclones) (7). Planetary and synoptic scale weather are often combined and referred to as macroscale weather.
Mesoscale systems range from ten to a few hundred kilometers and have lifetimes of a day or less (7). Two of the best-known examples of mesoscale weather systems are thunderstorms and tornadoes, along with local wind systems such as land & sea breezes and mountain winds (7).
British Columbia’s generalized climate and weather
The two major determinants of BC’s weather are its proximity to the Pacific Ocean (providing a reservoir of heat and moisture) and topography (chiefly the distribution and elevation of mountain ranges) (8).
Winter at the macroscale
During the winter months the Pacific Ocean spawns synoptic scale moisture laden weather systems (extra-tropical cyclones) over the North Pacific, predominantly as a result of the semi-permanent Aleutian low, that are then driven east by the planetary scale prevailing Westerlies (5, 8). These weather systems are often associated with fronts (boundaries between cold and warm air masses, delineated as red lines with half circles for warm fronts, blue lines with triangles for cold fronts, and a combination of the two for occluded fronts in meteorological reports such as those below in Figure 3) resulting in heavy precipitation and windy conditions (5, 8).
Figure 2: Satellite composite image of two extra-tropical cyclones in the North Pacific with the first beginning to make landfall on the BC coast on January 10th 2021. Check out Windy for excellent visualizations of these systems forming in the North Pacific and travelling towards BC next time you see prolonged periods of rain in the forecast!
Figure 3: Meteorological surface analysis of the same two storms. The first storm made landfall on January 10th bringing a period of heavy rain and winds to the south coast of BC over the following three days. The Victoria airport received 38 mm of precipitation and experienced wind gusts of 94 km/h, the Vancouver airport received 45 mm of precipitation and gusts of 91 km/h, and the North Shore received 60+ mm! Image source for Figures 2 & 3.
As these systems encounter successive mountain ranges their moisture laden air is forced to rise (a process known as orographic uplift) causing the air to cool and atmospheric water vapour to condense, resulting in heavy precipitation on windward slopes (8). This precipitation is especially abundant on the windward slopes of the Vancouver Island ranges, Haida Gwaii, and the mainland Coast Mountain range (8). On the leeward side of these mountains rain shadows are formed as air masses descend and are warmed by compression, causing clouds to dissipate as water droplets are converted to water vapour (8). The most prominent rain shadows, and thus the driest regions of the province, are located on the leeward side of the Coast Mountains within the valley bottoms of the south-central interior (8).
Figure 4: Distribution of mean annual precipitation in BC. Data taken from Climate BC and processed using QGIS.
This is why Victoria and the Gulf Islands receive far less precipitation than areas such as Tofino and the North Shore of Vancouver, despite their similar proximities to the ocean (as shown in Figure 4). This process of orographic uplift is repeated as air masses ascend the Columbia, Skeena, Omineca, Cassiar and finally the Rocky Mountains (8). The Rocky Mountains also act to impede the westward flow of cold continental Artic air masses from the east, giving BC more moderate winters than central Canada with the exception of the unprotected Great Plains Region of northeastern BC (8).
Summer at the macroscale
In the summer BC’s weather is again reliant on the Pacific, with the Aleutian low diminishing in strength as a large semi-permanent high-pressure centre (the North Pacific High) dominates, reducing the intensity and frequency of Pacific storms (8). This pressure system is located between California and Hawaii near the equator during the winter, shifting northward into the central-north Pacific during the summer (5). The dominance of the North Pacific High brings extended periods of clear skies and warm weather in the summer, except when it yields conditions for mesoscale systems (thunderstorms) generated by convective cells (heating of the earths surface due to solar energy, causing air to rapidly rise, cool and condense), especially in the interior (5).
Figure 5: Average annual frequencies of synoptic scale types in British Columbia. Taken from reference 5. See reference 5 for more in depth discussion and analysis of these synoptic types and the distribution of high and low pressure systems off the coast of and over BC.
While the descriptions of winter and summer above are of course simplifications, Figure 5 illustrates the average distribution of synoptic scale weather patterns throughout the year. As shown in Figure 5 synoptic Types 1, 2, and 8 are the most prominent in summer and are produced by the dominance of the North Pacific High. Conversely, the Aleutian Low is prominent in Types 3-5, and 7 (which occur year round having minima in summer) along with Types 9-13 (occurring mainly in the winter) (5).
In terms of extreme weather, BC is most commonly susceptible to powerful extra-tropical cyclones, atmospheric river events (e.g., Pineapple express), rain on snow events, mesoscale thunderstorms, and drought (5).
Distribution of climatic zones in BC
Figure 6: Distribution of mean annual temperature in BC. Data taken from Climate BC and processed in QGIS.
Mean Annual Air Temperature (MAT) varies across the province with distance from the coast (the ocean provides a heat reservoir in the winter and cooling in the summer), latitude (e.g., the amount of solar radiation received), and elevation (5). Higher MATs are found along the coast and inland within valley bottoms (see Figure 6 above) and decreases to the north and/or with increasing elevation (the earths surface acts as the source of heat for the troposphere and thus temperature decreases with elevation at a global average rate of 6.5°C/km) (5).
The Interior experiences higher summer temperatures (as it is removed from the cooling effects of the Pacific) than the BC coast in general, with the reverse being true for winter temperatures (5). The greatest MAT variations occur in the northern interior and the province overall experiences greater day-to-day temperature variations in winter (largely controlled by the origin of dominant air masses, e.g., Arctic continental versus maritime) and greater daily temperature ranges in summer due to seasonal variations in solar radiation (5).
The interactions of macroscale, synoptic scale, and mesoscale weather systems and topography produces distinct climatic patterns that vary with distance from the coast, elevation, exposure to the prevailing winds, and season (5). Broadly, the province can be classified into 16 climatic regimes, reflected by vegetation zones named for the dominant tree species in each zone (see Figure 7 below) (5).
Figure 7: The distribution of biogeoclimatic zones in BC based on mean annual temperature, mean annual precipitation, and the dominant vegetation species. Taken from reference 5.
There are also cyclical large scale (spatially large and temporally long) climate anomalies, known as teleconnections, bringing warmer & wetter and colder & drier than normal weather such as: The El Niño–Southern Oscillation (ENSO. Differentiated into La Niña and El Niño phases), the Pacific Decadal Oscillation (PDO), the Pacific North American Pattern, and the Arctic Oscillation (5). While there is random variability in weather and climate year to year, these planetary scale teleconnections have systematic variations on air temperature and precipitation patterns varying on scales of months (e.g., 6-18 months for ENSO) or decades (e.g., 20-30 years for PDO) and have considerable influence on weather and climate in BC over those timeframes (5).
Observed climate change in BC
From 1900-2013 BC has warmed an average of 1.4°C/century, higher than the global average of 0.85°C/century (9). However, this average differs greatly across the province with the northern regions warming at a rate of 1.6-2°C (similar to the level of warming experienced in the Arctic compared to the global average) while the southern coastal regions have warmed by 0.8°C (9).
Over 1900-2013 the average amount of precipitation province wide has increased by 12%/century (with a range of 10-21% in different regions across the province) (9). While precipitation does have high interannual variability, climate change will bring a shift to warmer wetter years, less precipitation falling as snow, greater year-to-year variability, and more extreme precipitation events (9).
Glacial coverage in BC has decreased by 2,525 km² over 1985-2005 (that’s equivalent to the area of more than 630 Vancouver Stanley Parks) while snow depth has significantly decreased in four regions of BC: 11% per decade in the Southern Interior, 10% per decade in the Central Interior, 7% per decade in the Southern Interior Mountains, and 6% per decade in the Georgia depression (9). Declining snowpack is a significant concern for BC, with impacts to instream flows (exacerbating issues facing already threatened salmonids), community water supply (especially in summer months), soil moisture, winter activities (skiing!), and aquifer recharge (9).
There are three primary factors affecting sea level in BC: 1. The influx of water from melting glaciers and ice sheets (specifically the Antarctic and Greenland ice sheets) 2. The thermal expansion of water as it is heated 3. Post glacial isostatic rebound (the slow process of the lithosphere decompressing following the retreat of ice sheets at the end of the Last Glacial Maximum). Over the past 50 years sea level rise has differed across the province with a 5 cm rise in Prince Rupert, 3 cm in Victoria, and 2 cm in Vancouver (9). Areas of BC most at risk from rising sea levels, erosion from wave action, and flooding are the Fraser Delta and the Naikoon region of Haida Gwaii (9).
Projected climate change in BC
Projecting climate change into the future is an extremely complex task given the innumerable uncertainties of our socio-economic systems (e.g., what actions will or will not be taken, population growth, the speed of our transition to alternative energies, economic growth, government policies etc.) along with the intricacies of the global climate system and positive feedback mechanisms (such as the so-called ‘permafrost bomb’). Climate change models are usually based on Representative Concentration Pathways (RCP), which each represent a separate radiative forcing.
A radiative forcing is the difference between the amount of shortwave energy received from the sun and absorbed by the Earth and the amount of longwave energy radiated back into space (see our first article to find out how the Earth’s climate changes). A positive radiative forcing equates to ‘extra’ energy being stored in the Earth’s climate system and a negative radiative forcing resulting in more energy leaving the Earth. With regard to anthropogenic climate change the greater the greenhouse gas effect the greater the radiative forcing.
RCP 2.6 and RCP 8.5 are commonly used to represent best and worst case scenarios for future global climate, representing 2.6 W/m² and 8.5 W/m² radiative forcing’s by 2100 respectively (10). This essentially means the storage of an additional 2.5-8.5 W/m² of energy across the entire surface of the Earth, raising the Earth’s global annual average temperature by between 0.9-2.3°C and 3.2-5.4°C by 2100 respectively, relative to a 1986-2005 baseline (10).
Figure 8: RCP scenarios and projected warming over the next century. Source.
Both temperature and precipitation are projected to continue increasing in BC across both low and high RCP scenarios with a median increase of 1.3°C through 2031-2050 relative to the 1986-2005 baseline for RCP 2.6 and a median increase of 1.9°C for RCP 8.5, while precipitation is projected to increase by 4.3% and 5.6% for each RCP respectively (10).
For Metro-Vancouver specifically (in which over 40% of BC’s population lives), the region can expect a doubling in the number of summer days above 25°C by the 2050’s along with the 1-in-20 hottest temperature (i.e., a temperature that has a 5% chance of occurring in any given year) projected to increase by 4°C from 34°C to 38°C (11). A 5% increase in precipitation is expected in the region by the 2050’s, however the amount of rain in summer is expected to decrease by 20% lengthening dry spells from 21 consecutive to 26 consecutive days (11). Critically, despite more precipitation being projected less will fall as snow, decreasing the April 1st snowpack depth in watersheds in the region by 60% by the 2050’s (11).
Heating requirements will drastically drop in the winter (an estimated 29% reduction by the 2050’s) while cooling requirements in the summer will increase by nearly six times current levels (11). Water shortages and drought are likely to become more pronounced along with increased forest fire activity in summer months, while more intense extra-tropical cyclones can be expected in the winter (11). See What Will the World Look Like, 2°C Warmer? for a short informative video comparing future climate in Vancouver to that of Kolkata, India.
Why is it important to understand climate change?
A change of just a few degrees in global annual average temperature can have drastic impacts on the way the Earth looks and the functioning of its many spheres. When the Earth’s global annual average temperature was about 6.1°C colder than it is today during the Last Glacial Maximum (about 19,000-23,000 years ago) and CO₂ concentrations were just 180 parts per million (ppm, compared to 415 ppm today and 280 ppm before the industrial revolution) much of North and South America, Europe, and parts of Asia were covered in thick ice sheets, with southern BC being covered by glacial ice up to 2,000 meters thick! (12, 13).
While the global climate will continue to warm and change over the 21st century regardless of our collective actions due to the residency time of GHG’s in the atmosphere, we can still mitigate and prevent future catastrophic warming and its impacts.
There are many technological innovations, public policies, and grass root actions occurring in BC, Canada, and around the world to mitigate and adapt to climate change (which may be the topic for our next article!) along with our own actions & decisions as consumers and citizens. We hope that understanding the science behind climate and weather will inspire you to act across your spheres of influence in small and big ways to contribute to a brighter and more prosperous future.
If you have any questions, would like something explained in more detail, or have a topic you want us to cover in the future please comment below or reach out to us via email!
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Works cited
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2. World Meteorological Organization. (2020). State of the Global Climate 2020 Provisional Report. Geneva: World Meteorological Organization.
3. Lazo, J. K., Lawson, M., Larsen, P. H., & Waldman, D. M. (2011). U.S. economic sensitivity to weather variability. American Meteorological Society, 709-720.
4. Scheffers, B. R., De Meester, L., Bridge, T. C., Hoffmann, A. A., Pandolfi, J. M., Corlett, R. T.….. & Watson, J.E.M. (2016). The broad footprint of climate change from genes to biomes to people. Science, 354(6313), 719-731.
5. Pike, R.G., T.E. Redding, R.D. Moore, R.D. Winker and K.D. Bladon (editors). 2010. Compendium of forest hydrology and geomorphology in British Columbia. B.C. Min. For. Range, For. Sci. Prog., Victoria, B.C. and FORREX Forum for Research and Extension in Natural Resources, Kamloops, B.C. Land Manag. Handb. 66. www.for.gov.bc.ca/hfd/pubs/Docs/Lmh/Lmh66.htm
6. Spohn, T., Breuer, D., & Johnson, T. V. (2014). Encyclopedia of the Solar System Third Edition. Amsterdam: Elsevier.
7. Britannica. Scale classes. (n.d.). Retrieved from Britannica: https://www.britannica.com/science/climate-meteorology/Scale-classes
8. Pojar, J. and D.V. Meidinger. 1991. British Columbia: The environmental setting. In: Meidinger, D.V. and J. Pojar (Compilers and editors). 1991. Ecosystems of British Columbia. B.C. Min. For., Res. Br., Victoria, B.C. Spec. Rep. Ser. 6. Chap. 3, pp. 39-67.
9. Government of British Columbia. (n.d.). Climate Change Indicators. Retrieved from Government of British Columbia: https://www2.gov.bc.ca/gov/content/environment/research-monitoring-reporting/reporting/environmental-reporting-bc/climate-change-indicators
10. Environment and Climate Change Canada. (2018). Scenarios and climate models. Retrieved from Government of Canada: https://www.canada.ca/en/environment-climate-change/services/climate-change/canadian-centre-climate-services/basics/scenario-models.html
11. Metro Vancouver. (2016). Climate Projections for Metro Vancouver. Vancouver: Metro Vancouver.
12. Tierney, J. E., Zhu, J., King, J., Malevich, S. B., Hakim, G. J., & Poulsen, C. J. (2020). Glacial cooling and climate sensitivity revisted. Nature, 584, 569-573.
13. Ryder, J. M., Fulton, R. J. & Clague, J. J. (1991). The Cordilleran Ice Sheet and the Glacial Geomorphology of Southern and Central British Colombia. Géographie physique et Quaternaire, 45 (3), 365–377. https://doi.org/10.7202/032882ar