7.2 Climate change – causes and impacts

Significant ideas:

  • Climate change has been a normal feature of the Earth’s history, but human activity has contributed to recent changes.
  • There has been significant debate about the causes of climate change.
  • Climate change causes widespread and significant impacts on a global scale.

Knowledge and understanding:

  1. Climate describes how the atmosphere behaves over relatively long periods of time, whereas weather describes the conditions in the atmosphere over a short period of time.
  2. Weather and climate are affected by oceanic and atmospheric circulatory systems.
  3. Human activities are increasing levels of greenhouse gases (GHGs, such as carbon dioxide, methane and water vapour) in the atmosphere, which leads to:
    • an increase in the mean global temperature
    • increased frequency and intensity of extreme weather events
    • the potential for long-term changes in climate and weather patterns
    • rise in sea level.
  4. The potential impacts of climate change may vary from one location to another and may be perceived as either adverse or beneficial. These impacts may include changes in water availability, distribution of biomes and crop growing areas, loss of biodiversity and ecosystem services, coastal inundation, ocean acidification, and damage to human health.
  5. Both negative and positive feedback mechanisms are associated with climate change and may involve very long time lags.
  6. There has been significant debate due to conflicting EVSs surrounding the issue of climate change.
  7. Global climate models are complex and there is a degree of uncertainty regarding the accuracy of their predictions.

Applications and skills:

  • Discuss the feedback mechanisms that would be associated with a change in
    mean global temperature.
  • Evaluate contrasting viewpoints on the issue of climate change.


  • The impacts of the climate change are global and require coordinated international action.

Theory of knowledge:

  • There has been considerable debate about the causes of climate change—does our interpretation of knowledge from the past allow us to reliably predict the future?


  • Systems and models (1.2)
  • Energy and equilibria (1.3)
  • Threats to biodiversity (3.3)
  • Access to fresh water (4.2)
  • Aquatic food production systems (4.3)
  • Terrestrial food production systems and food choices (5.2)
  • Introduction to the atmosphere (6.1)
  • Stratospheric ozone (6.2)
  • Human population carrying capacity (8.4)