6.2 Climate change—causes and impacts

Objective notes

15 learning objectives

6.2.1Climate definition

• Typical atmospheric conditions

• Seasonal temperature and precipitation variations

6.2.2Anthropogenic CO₂ emissions

• Atmospheric CO₂ concentration rising significantly

• Accelerated since 1950

• Traced to Industrial Revolution (late 18th century)

6.2.3Ice core, tree ring, sediment data

• Positive correlation: atmospheric CO₂ and global temperatures

• Data for past 800,000 years

6.2.4Enhanced greenhouse effect

• Anthropogenic GHG emissions

• Led to global warming and climate change

6.2.5Climate change impacts on ecosystems

• Local to global scales

• Affects resilience, leads to biome shifts

• Examples: coral bleaching, desertification, ocean circulation changes

6.2.6Climate change impacts on societies

• Various scales and socio-economic conditions

• Impacts resilience

• Health, water supply, agriculture, infrastructure

6.2.7Climate change models

• Systems diagrams with feedback loops

• Solar radiation variations, albedo changes, methane release

6.2.8Climate change planetary boundary

• Evidence suggests already passed

6.2.9Perspectives on climate change

• Influenced by many factors

• Individual and societal levels

6.2.10(HL)—Climate data collection

• Weather stations, observatories, radar, satellites

• Direct measurements: temperature, GHG concentrations

• Indirect (proxies): ice core isotopes, dendrochronology, peat pollen

6.2.11(HL)—Global climate models

• Manipulate inputs to predict outputs

• Uncertainty in inputs and outputs

• Hindcasting: test validity

6.2.12(HL)—Climate model scenarios

• Predict impacts: sea-level rise, temperature, precipitation

6.2.13(HL)—Critical thresholds and tipping points

• Earth may approach critical threshold → new equilibrium

• Examples: Antarctic ice sheet melting, Atlantic circulation slowing, Amazon-Cerrado transition

6.2.14(HL)—Tipping cascades

• Two or more tipping points interact

• Predictions very uncertain

6.2.15(HL)—Climate justice

• Countries vary in responsibility and vulnerability

• Least responsible often most vulnerable

• Political, economic, equity implications