Key Idea: Topic 6.1 covers how the atmosphere is structured, why it supports life, how Earth’s energy budget works (short-wave in, long-wave out), and the role of the natural greenhouse effect and albedo in regulating temperature.
🌬️ Atmosphere layers (core exam ones)
- Troposphere: weather + greenhouse effect; temperature decreases with altitude
- Stratosphere: ozone layer; temperature increases with altitude
☀️ Energy budget (Sun = short, Earth = long)
- Sun delivers short-wave radiation (visible/UV)
- Earth re-emits long-wave (infrared)
- Temperature stability needs energy in = energy out
Short-wave = incoming from Sun. Long-wave = outgoing heat from Earth.
🏠 Natural greenhouse effect
- Short-wave passes through → surface warms
- Surface emits long-wave
- Greenhouse gases absorb + re-emit long-wave back down
- Earth stays ~33°C warmer than without it
🧊 Albedo + feedback
- High albedo (ice/snow/cloud) reflects more; low albedo (ocean/forest) absorbs more
- Ice-albedo is a positive feedback loop (melting → darker surface → more absorption → more warming)
✅ Exam Checklist
- Troposphere vs stratosphere (role + temperature trend)
- Short-wave vs long-wave definition
- 5-step greenhouse mechanism
- Explain ice-albedo positive feedback