IB Geography Unit 2: Global climate—vulnerability and resilience

What Unit 2 covers

Unit 2 is the second core unit. The causes of global climate change: the Earth's energy balance, with insolation, terrestrial radiation and albedo; the natural greenhouse effect and the enhanced greenhouse effect; the sources of greenhouse gases, from fossil fuels to the methane from flooded rice fields; natural changes such as the cooling after large volcanic eruptions; and the feedback loops and tipping points, such as thawing permafrost, that can speed change up. The consequences of global climate change: sea-level rise and ocean acidification, the impacts on people and places, and why some communities are more vulnerable than others. Responding to global climate change: mitigation and adaptation, carbon capture and storage, cap and trade and carbon offsetting, geo-engineering, the IPCC, and agreements from the Kyoto Protocol to the Paris Agreement.

Where students slip

• Water vapour, not CO₂, makes the largest contribution to the natural greenhouse effect. The enhanced greenhouse effect is driven by the CO₂, methane and other gases human activity adds; water vapour rises as a feedback, because warmer air holds more of it.
• Melting sea ice barely raises sea level, because floating ice already displaces its own weight of water. Sea level rises through the thermal expansion of warming seawater and the melting of land ice: glaciers and the Greenland and Antarctic ice sheets.
• Mitigation tackles the cause, by cutting greenhouse gas emissions or enhancing carbon sinks; adaptation adjusts to the effects. Carbon capture and storage is mitigation; a sea wall or a drought-resistant crop is adaptation.