A process where warming triggers changes that cause more warming — e.g. melting Arctic ice exposes dark ocean, which absorbs more heat, melting more ice (ice-albedo feedback). Learn it step by step →
Water & Carbon Cycles is a core part of A-Level Geography. Revise the key concepts and common mistakes below, then lock them in with the free games.
Key concepts
Positive feedbackInitial change is amplified, e.g. ice-albedo loop accelerating melt.
Negative feedbackInitial change is dampened, e.g. increased CO2 boosting plant growth that absorbs CO2.
Ice-albedo feedbackMelting ice exposes darker surface, absorbs more heat, drives further melt.
Permafrost thawReleases stored methane and CO2, amplifying warming.
DeforestationReduces evapotranspiration and carbon sequestration; Amazon losing ~10000 km^2/yr.
Ocean acidificationRising CO2 lowers ocean pH (from 8.2 pre-industrial to ~8.1 today).
Drainage basinArea of land drained by a river and its tributaries; open subsystem of water cycle.
Water balancePrecipitation = evapotranspiration + runoff + storage change.
Lag timeTime between peak rainfall and peak discharge.
Peak dischargeMaximum river flow following storm event, in m^3/s (cumecs).
ThroughflowLateral movement of water through soil downslope to channel.
BaseflowGroundwater seepage maintaining river flow between storms.
StoreA reservoir holding water or carbon for a measurable time (e.g. oceans, atmosphere, biosphere).
FluxRate of transfer between stores, measured in Gt/yr or km^3/yr.
What your exam board covers
Where Water & Carbon Cycles sits in each exam board's specification. Tap a board to see what it lists.
Questions where students often pick the tempting wrong answer — make sure you know the right one:
What is a positive climate feedback loop?✗ Positive feedback means a good outcome for the climate.✓ A process where warming triggers changes that cause more warming — e.g. melting Arctic ice exposes dark ocean, which absorbs more heat, melting more ice (ice-albedo feedback).
How do humans affect the carbon cycle?✗ Humans only affect the carbon cycle by breathing out CO2.✓ By burning fossil fuels (releasing stored geological carbon to the atmosphere) and deforestation (reducing the biosphere store and releasing carbon).
What is lag time on a storm hydrograph?✗ Lag time is how long the storm itself lasts.✓ The time between peak rainfall and peak river discharge — affected by drainage basin shape, land use, soil saturation and vegetation.
Lag time refers to:✗ Time between storm start and storm end✓ Time between peak rainfall and peak discharge
What is the difference between physical and economic water scarcity?✗ Water scarcity only happens in dry countries.✓ Physical scarcity is insufficient water supply for demand (e.g. arid regions); economic scarcity is inability to access available water due to lack of infrastructure or investment, despite water being present.
Practise Water & Carbon Cycles — free games
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