Lesson 6 of 7
Climate change
Goal: Explain how human activity affects the climate.
Greenhouse gases keep the Earth warm. Human activity is adding more of them to the air, so the Earth is getting warmer.
- The greenhouse effect. The Sun warms the ground. The warm ground gives out energy as radiation. Carbon dioxide and methane absorb some of it, so less energy escapes to space.
- The cause. Burning fossil fuels in power stations, vehicles and homes adds carbon dioxide to the air. Cutting down forests leaves fewer trees to take it in.
- The evidence. Measurements show that the carbon dioxide in the air has risen by half since about 1750. The average surface temperature of the Earth has risen by about 1 °C. This is global warming.
- The effects. Ice sheets and glaciers melt and sea level rises. There is more extreme weather: heatwaves, droughts, floods and stronger storms.
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Key words in this lesson
Fossil fuel Coal, oil or natural gas, formed from the remains of dead organisms
Greenhouse gas A gas that stops some energy escaping from the Earth to space
Global warming The gradual rise in the average surface temperature of the Earth