Climate Change
Drivers and mechanisms
Climate is driven by the energy balance between incoming solar radiation and outgoing longwave radiation. Greenhouse gases (carbon dioxide, methane, nitrous oxide, water vapour) absorb outgoing infrared and re-radiate energy, warming the surface. Radiative forcing measures the change in energy balance (watts per square metre) caused by a factor such as greenhouse gas concentration, aerosols, or albedo change. Human activities - fossil fuel combustion, deforestation, agriculture, and industry - have raised greenhouse gas concentrations since industrialisation.
Concepts to master
Distinguish weather (short-term) from climate (long-term averages and variability). Know the difference between a climate driver (external forcing) and a feedback (internal response), and identify key feedbacks: water vapour (positive), ice-albedo (positive), and increased plant growth or weathering (negative). Understand proxy evidence - ice cores, tree rings, sediment cores, corals - and the difference between natural variability (orbital cycles, solar variation, volcanism) and anthropogenic forcing. Learn mitigation (reducing emissions, carbon sinks) versus adaptation (managing impacts such as sea-level rise and heatwaves).
Common traps
Students often cite a single cold day as evidence against warming; that confuses weather with climate. Another trap is treating a feedback as a driver. Questions may ask you to separate correlation from causation in temperature and CO₂ records.
Worked example
If a forcing of +2.0 W/m² acts on a system with a climate sensitivity parameter of 0.8 °C per W/m², the equilibrium warming is about 1.6 °C. This illustrates how forcing and sensitivity combine to produce a temperature response.