Weather, climate and climate change

Last time

Before we start: last time, in Water supply and environmental risks, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.

Today and over decades

Weather is what happens today: rain, sun, wind. Climate is the average weather over many years. Both are measured with instruments at weather stations. And climate is changing, partly because of human activity. This lesson covers both.

Measuring the weather

Temperature is measured with a thermometer; maximum and minimum thermometers record the day's extremes. Rainfall with a rain gauge; wind direction with a wind vane; wind speed with an anemometer. Air pressure with a barometer, and humidity with a wet and dry bulb thermometer, called a hygrometer.

The Stevenson screen

Thermometers are kept in a Stevenson screen: a white wooden box on legs. It is white to reflect sunlight, has slatted sides to let air flow, and stands above the ground, away from buildings. This gives accurate air temperatures, not heated by direct sun or the ground.

Clouds and rain

When moist air rises, it cools, and water vapour condenses into droplets, forming clouds. Relief rain forms when air is forced over mountains. Convectional rain forms when the ground heats air, which rises. Frontal rain forms when warm air meets cold air and is pushed upwards.

Describing rainfall patterns

Describe the overall pattern: where it is highest and lowest, and the general trend, such as decreasing inland. Use directions and place names from the figure, and anomalies that break the pattern. If told not to use statistics, describe with words only.

The greenhouse effect

Greenhouse gases, such as carbon dioxide and methane, trap some of the heat given off by the Earth, keeping it warm enough for life. More greenhouse gases trap more heat: the enhanced greenhouse effect, leading to global warming. Natural causes of climate change include volcanic eruptions and changes in the Sun's output and the Earth's orbit.

Human causes

Burning fossil fuels for power, transport and industry releases carbon dioxide. Deforestation removes trees that absorb carbon dioxide. Farming, such as rice paddies and cattle, releases methane.

Effects of climate change

Rising sea levels, as ice melts and seawater expands, threaten low-lying coasts. More extreme weather: heatwaves, droughts, floods and stronger storms. Effects on farming, water supply, ecosystems and health. Responses: renewable energy, planting trees, and adapting, such as flood defences.

Weather instruments

Each instrument and what it measures.

Mistakes that lose marks

Mistake one: confusing weather with climate. Mistake two: mixing up the anemometer and the wind vane. Mistake three: using statistics when told not to. The fix: the right term, the right instrument, and the instructions.

The full-marks tip

The full-marks tip: for climate change, separate natural and human causes, then give effects and responses. When describing a pattern, give the trend, the extremes, and an anomaly.

On one card

So, on one card: weather and climate. Keep it for revision.