Core 2 • Section 2.1
Causes of Global Climate Change
How atmospheric processes, feedback loops and human activity alter Earth’s energy balance.
How natural and human processes affect global energy balance
The atmospheric system
Natural greenhouse effect, incoming short-wave radiation, outgoing long-wave radiation and dynamic equilibrium.
Earth’s climate begins with an energy budget. Some incoming solar energy is reflected, while the rest is absorbed and re-radiated. Greenhouse gases absorb part of that outgoing energy, warming the lower atmosphere enough to sustain life.
Energy-budget sketch
- Draw the Sun, atmosphere and surface.
- Add incoming short-wave and outgoing long-wave radiation.
- Show reflection, absorption and re-radiation.
- Explain why the natural greenhouse effect is essential.
Feedback loops and tipping points
Positive feedback amplifies an initial change; negative feedback counteracts it.
Climate feedbacks link components of the Earth system. Melting ice reduces albedo, thawing permafrost can release methane, and changing vegetation alters carbon storage. A tipping point is a threshold beyond which change may become self-sustaining or difficult to reverse.
Causal-loop enquiry
Create two chains using change → process → consequence → feedback. Annotate each arrow and identify where evidence is strong, uncertain or contested.
Solar variation, dimming and albedo
Changes in radiation and reflectivity alter the amount of energy retained by the Earth system.
Solar output varies, while aerosols and particulates can produce global dimming. Albedo describes surface reflectivity: bright ice reflects more energy than dark ocean or land, creating an important warming feedback as ice melts.
Compare mechanisms
For solar variation, aerosols and albedo, identify the forcing, the direction of temperature change, the timescale and whether human activity influences it.
Methane release feedback
Warming can unlock carbon stored in wetlands, permafrost and methane hydrates.
Methane is shorter-lived than carbon dioxide but traps more heat per molecule over shorter timescales. Distinguish natural feedback-driven emissions from human sources such as fossil-fuel extraction, livestock, rice cultivation and waste.
The enhanced greenhouse effect
Combustion, land-use change and production systems increase atmospheric greenhouse-gas concentrations.
The enhanced greenhouse effect results from additional carbon dioxide, methane and nitrous oxide. Emissions can be counted by territory, consumption, sector or historical responsibility—each reveals a different geography of responsibility.
Emissions-accounting challenge
- Compare total and per-capita emissions.
- Contrast territorial and consumption-based accounting.
- Identify the sectors driving emissions.
- Write a judgement: which measure best represents responsibility?