Climate vs. weather
Weather is what’s happening in the atmosphere right now: sunny, rainy, cold or windy. Climate is the average pattern of weather over a long time, usually 30 years or more.
| Weather | Climate |
|---|---|
| "It’s snowing in Winnipeg today." | "Winnipeg has long, cold winters and warm summers." |
| Changes hour to hour | Changes over decades or longer |
| Helps you decide what to wear today | Helps you decide what clothes to own |
What controls climate?
1. Latitude
Latitude is the most important factor. Near the equator, sunlight strikes the ground nearly straight on, concentrating its energy. Near the poles, sunlight hits at a low angle and spreads out, so it’s much cooler.
2. Distance from water
Water heats and cools more slowly than land.
- Coastal (maritime) climates have mild winters and cool summers. Victoria rarely gets very cold.
- Inland (continental) climates have hot summers and cold winters. Winnipeg can reach above 30 °C in summer and below −30 °C in winter.
3. Elevation
Temperature usually drops about 6.5 °C for every 1000 m you climb. That’s why mountaintops can have snow even in summer.
4. Ocean currents
Warm currents bring mild weather; cold currents bring cool weather. The warm Gulf Stream and North Atlantic Drift keep Britain much milder than Labrador, at the same latitude.
5. Prevailing winds
Winds bring moisture or dryness. Westerly winds blowing off the Pacific bring heavy rain to BC’s coast.
6. Mountains
Mountains block moist air. The side facing the wind gets rain; the far side, called the rain shadow, is dry. Vancouver is rainy, but the interior of BC, east of the Coast Mountains, is much drier, and parts of the Okanagan are semi-desert.
Climate zones
| Climate zone | Location | Features |
|---|---|---|
| Tropical | Near the equator | Hot all year; often very wet |
| Dry (arid) | Around 30° N and S, and rain shadows | Little rain; large daily temperature swings |
| Temperate | Middle latitudes | Four seasons; moderate rain |
| Continental | Inside large continents in the north | Hot summers, very cold winters |
| Polar | Near the poles | Very cold; little precipitation |
| Highland | High mountains | Changes with elevation |
Most of Canada has continental or subarctic climates. The far north is polar, and the BC coast is temperate maritime.
Climate and life
Climate determines what can live in a place. Large regions with similar climate, plants and animals are called biomes.
| Biome | Climate | Life |
|---|---|---|
| Tundra | Very cold; short summers | Mosses, lichens, caribou |
| Boreal forest (taiga) | Cold winters; short summers | Spruce, pine, moose, lynx |
| Temperate forest | Four seasons | Maple, oak, deer |
| Grassland (prairie) | Hot summers, cold winters, moderate rain | Grasses, bison |
| Desert | Very dry | Cacti, lizards |
| Tropical rainforest | Hot and wet all year | Huge variety of species |
The greenhouse effect
Some gases in the atmosphere, like carbon dioxide, methane and water vapour, trap heat. This natural greenhouse effect keeps Earth about 33 °C warmer than it would otherwise be. Without it, Earth’s average temperature would be about −18 °C.
Climate change
Earth’s climate has changed many times through ice ages and warm periods, usually over thousands of years. Today it’s changing much faster. Burning fossil fuels has increased carbon dioxide in the air, strengthening the greenhouse effect.
- Earth’s average temperature has risen about 1.2–1.3 °C since the late 1800s.
- Canada is warming about twice as fast as the global average, and the Arctic even faster.
- Effects include melting sea ice, more intense wildfires and heat waves, rising seas and shifting habitats.
Responding to climate change involves reducing emissions (switching to clean energy, using less fuel) and adapting to changes already underway.
Common mistakes
- Mixing up weather and climate.
- Thinking a cold day disproves climate change.
- Thinking places at the same latitude always have the same climate. Water, mountains and currents matter.
Try it yourself
- Compare climate graphs (average monthly temperature and precipitation) for Vancouver, Winnipeg and Iqaluit. Explain the differences.
- Find a city at the same latitude as yours on another continent. How is its climate similar or different?
- Place two thermometers in sealed jars, one with extra CO₂ from a fizzing antacid tablet. Put both in sunlight and compare.
Quick recap
- Climate is long-term average weather.
- Latitude, water, elevation, currents, winds and mountains shape climate.
- Climate zones and biomes have characteristic plants and animals.
- The greenhouse effect keeps Earth warm.
- Human activities are causing rapid climate change.