Human Impact: Climate Change

This lesson covers the enhanced greenhouse effect, evidence for climate change, effects on biodiversity, and mitigation strategies, as required by the Edexcel A-Level Biology specification (9BI0), Topic 10 -- Ecosystems.

---

The Greenhouse Effect

The natural greenhouse effect is essential for life on Earth:

1. The Sun emits short-wave solar radiation (visible light, UV) that passes through the atmosphere
2. The Earth's surface absorbs this radiation and re-emits it as long-wave infrared (heat) radiation
3. Greenhouse gases (CO2, methane, water vapour, nitrous oxide) in the atmosphere absorb some of this outgoing infrared radiation
4. The absorbed energy is re-emitted in all directions, including back towards the Earth's surface
5. This keeps the Earth's average temperature at approximately 15 degrees C (without it, it would be about -18 degrees C)

---

The Enhanced Greenhouse Effect

Human activities have increased the concentration of greenhouse gases in the atmosphere, intensifying the natural greenhouse effect and causing global warming -- a sustained increase in the Earth's average surface temperature.