Climate Change and Greenhouse Gases

This lesson covers the greenhouse effect, greenhouse gases, and climate change as required by the Edexcel GCSE Chemistry specification (1CH0). You need to understand how greenhouse gases keep the Earth warm, how human activities are increasing their concentrations, the evidence for climate change, and why there is debate about the extent of human impact.

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The Greenhouse Effect

The greenhouse effect is a natural process that keeps the Earth warm enough to support life. Without it, the Earth's average temperature would be about −18 °C instead of the current +15 °C.

How It Works

1. Short-wavelength radiation (visible light and ultraviolet) from the Sun passes through the atmosphere and reaches the Earth's surface.
2. The Earth's surface absorbs this energy and warms up.
3. The warm surface re-emits the energy as long-wavelength infrared radiation (heat).
4. Greenhouse gases in the atmosphere absorb some of this infrared radiation.
5. The greenhouse gases then re-emit the infrared radiation in all directions — some goes back out to space, but some is radiated back towards the Earth.
6. This keeps the Earth warmer than it would otherwise be.