SL and HL: Subtopic 2.4 Climate and biomes: Weather describes atmospheric conditions over a short period, whereas climate describes typical atmospheric conditions over relatively long periods.
The Reasoning
Weather is the immediate state of the atmosphere at a particular place and time. It includes variables such as temperature, precipitation, wind speed, cloud cover, humidity and atmospheric pressure. For example, heavy rainfall in London on one afternoon is weather.
Climate is identified by analysing weather data collected over many years. Long-term averages, seasonal patterns, ranges and frequencies reveal what conditions are typical for a location. London’s repeated pattern of relatively mild temperatures and year-round precipitation is therefore part of its climate.
| Feature | Weather | Climate |
|---|---|---|
| Timescale | Hours, days or weeks | Decades or longer |
| Focus | Current or short-term atmospheric conditions | Long-term patterns and typical conditions |
| Example | A heatwave lasting five days | Hot, dry summers occurring regularly in a Mediterranean climate |
| Variability | Can change rapidly | Changes more gradually, although long-term shifts occur |
| ESS application | Describes individual atmospheric events | Helps explain biome distribution and climate change |
Climate influences the distribution of biomes because long-term temperature and precipitation patterns affect primary productivity, vegetation and species distributions. A single rainy day does not transform a desert into a forest because biome development depends on persistent climatic conditions.
A common misconception is that one cold day disproves global warming. This is incorrect: one event is weather, while global warming is a long-term rise in average global temperature. However, climate change can alter the probability, intensity and distribution of weather events, affecting societies unevenly and creating environmental justice concerns.
Exam Technique
For a distinguish question, refer to both terms and make the timescale contrast explicit. For an explain question, connect long-term temperature and precipitation patterns to biome distribution. Avoid defining climate simply as “average weather” without stating that it concerns typical conditions over relatively long periods.