6.1.4—Greenhouse effect
- Syllabus
- First assessment 2026
- Objective
- 6.1.4
- Level
- SL
Separate the Natural and Enhanced Greenhouse Effects
The natural greenhouse effect makes Earth habitable; human increases in long-lived greenhouse gases enhance it and warm the climate.
Short-wave sunlight enters; the surface emits long-wave infrared; gases absorb and re-emit some energy. Extra GHGs require a warmer surface–troposphere system to restore balance. Global warming is temperature trend; climate change includes wider responses.
Adding CO₂ does not add sunlight; it slows outgoing infrared, so equilibrium is restored at a higher mean temperature.
Specify natural versus enhanced effect and the short-wave/long-wave energy pathway.
The atmosphere does not warm by trapping all heat forever; energy still leaves, but the balance shifts.