global systems

Atmosphere

Layer of gases surrounding Earth; contains oxygen, nitrogen, and carbon dioxide.

Lithosphere

Earth's solid outer layer (rocks, soil, and landforms).

Hydrosphere

All water on Earth—oceans, rivers, lakes, groundwater, and ice.

Biosphere

All living things and ecosystems interacting with the other spheres.

Greenhouse effect

Natural process where gases trap heat, keeping Earth warm enough for life.

Main greenhouse gases

Carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O), and chlorofluorocarbons (CFCs).

Enhanced greenhouse effect

Human activities (burning fossil fuels, deforestation) increase gas concentrations → more heat trapped.

Link to global warming

More greenhouse gases = more trapped heat = rising global temperatures.

International action

Paris Agreement (2015) aims to limit global warming to under 2°C.

Most harmful gas

Carbon dioxide (most abundant and long-lasting).

Biodiversity

Variety of all living organisms on Earth.

Importance of biodiversity

Maintains ecosystem balance, food chains, and resilience to change.

Threats to biodiversity

Climate change, pollution/over-fertilisation, overexploitation, invasive species, deforestation/urbanisation.

Long-term effects of biodiversity loss

Species extinction, food chain collapse, less ecosystem stability.

The Carbon Cycle

Movement of carbon between atmosphere, living things, oceans, and Earth.

Sinks (store carbon)

Oceans, forests.

Sources (release carbon)

Respiration, combustion.

Release agent

Human activity (burning fossil fuels).

Permafrost

Permanently frozen ground in Arctic regions.

Melting permafrost effect

Releases methane → increases global warming.

The Water Cycle

Processes: Evaporation, condensation, precipitation, runoff, groundwater, transpiration.

Human impacts on water cycle

Pollution, deforestation, overuse.

Climate change

Long-term shifts in weather patterns and temperature.

Carbon footprint

Total greenhouse gases emitted by a person/group.