Key Idea: Topic 6.2 explains the evidence for climate change (direct + proxy), key trends (temperature, CO₂, sea level, ice), why current warming is mainly anthropogenic, and the major impacts on physical systems, ecosystems, and societies.
📈 Evidence: direct vs proxy
Direct measurements: Instrument temperature records. CO₂ monitoring. Satellites (ice extent, sea surface temperature). Sea level (tide gauges + satellites).
Proxy data: Ice cores. Tree rings. Corals. Sediment/pollen records.
Evaluation skill: direct = precise but short timeframe; proxy = long timeframe but interpreted.
🔥 Causes: natural vs anthropogenic
- Natural factors exist (orbital cycles, volcanoes, solar variability) but don’t explain the rapid post-1950 trend
- Anthropogenic: fossil fuels (CO₂), deforestation (CO₂), agriculture (CH₄, N₂O), industry (F-gases)
🌍 Impacts (physical + ecosystems + people)
- Physical: warming, shifting rainfall, extreme events, glacier/ice loss, sea-level rise, permafrost thaw
- Ecosystems: range shifts, phenology changes, coral bleaching, ocean acidification, food web disruption
- Societies: food/water insecurity, health risks, infrastructure damage, displacement + climate justice
✅ Exam Checklist
- Define proxy data + give 2 examples
- Name 3 anthropogenic GHG sources and the gas
- Explain sea-level rise causes (thermal expansion + land ice melt)
- Give one physical + one ecosystem + one social impact with cause-effect