Key Terms: Water, Carbon & Life on Earth (AQA A Level Geography): Revision Note

Key role in supporting life - key terms

Carbonate formation – The process by which marine organisms use calcium carbonate to form shells and skeletons, supporting life in oceans.

Evapotranspiration – The combined loss of water from the Earth's surface through evaporation and plant transpiration, influenced by CO₂ levels.

Lithosphere - The solid, outer part of the Earth.

Ocean acidification - Decreasing pH levels due to increasing levels of CO₂ absorbed by ocean/sea water.

Photosynthesis – A process in which plants absorb CO₂ and water to produce glucose and oxygen, critical for life and carbon cycling.

Respiration – The process by which living organisms release energy from glucose, producing CO₂ and water as by-products.

Soil erosion – The removal of topsoil by wind or water, which is worsened by limited vegetation and reduces carbon and nutrient cycling.

Water, carbon and climate change - key terms

Albedo effect – The reflection of solar radiation by surfaces. As ice melts, darker ocean surfaces absorb more heat, contributing to warming.

Carbon cycle feedback loop – A series of cause-and-effect processes where warming leads to increased carbon emissions, which in turn causes more warming.

Dimethylsulphide (DMS) – A compound released by marine phytoplankton that promotes cloud formation and influences climate regulation.

Greenhouse gases – Gases like carbon dioxide, methane and water vapour that trap heat in the atmosphere, affecting global temperatures.

Methane – A potent greenhouse gas released by permafrost thawing and other processes, contributing significantly to climate change.

Negative feedback – A response that counteracts changes in a system, helping maintain stability (e.g. increased clouds reflecting sunlight and cooling Earth).

Permafrost – Permanently frozen ground that stores methane and CO₂. When it melts, greenhouse gases are released, enhancing warming.

Phytoplankton – Microscopic marine organisms that absorb CO₂ through photosynthesis and help regulate the global carbon cycle.

Positive feedback – A process that amplifies change, such as warming increasing ice melt and reducing the albedo effect, causing further warming.

Thermohaline circulation – A global ocean current system driven by differences in temperature and salinity that helps distribute heat and carbon.

Tipping point - A tipping point happens when a changing process goes to a point where it cannot be reversed — a glass of water tips over, the spilt water can't be put back in the glass.

Mitigating impacts of climate change - key terms

Agroforestry – A land-use system that integrates trees with crops and/or livestock to increase carbon storage and reduce emissions.

Afforestation – The planting of trees in areas not previously forested, which increases carbon sequestration and helps reduce CO₂ levels.

Cap and trade – A system where countries or companies are given emission allowances and can buy or sell unused carbon credits.

Carbon capture and storage (CCS) – A technology that captures CO₂ emissions from sources like power stations and stores them underground.

Carbon credits – Permits that allow a country or organisation to emit a certain amount of CO₂, tradable if emission caps are met.

Carbon farming – Replacing crops with species that absorb more atmospheric CO₂, helping to enhance carbon sequestration in soils.

Clean Development Mechanism – An arrangement where high-income countries invest in emission-reducing projects in lower-income countries.

Debt-for-nature swap – An agreement where debt is forgiven in exchange for a commitment to environmental protection, such as forest conservation.

Genetic engineering – The modification of crops to improve their resistance to climate change and increase their ability to absorb CO₂.

Kyoto Protocol – A 1997 international treaty that aimed to legally bind countries to reduce greenhouse gas emissions, though not all signed or met targets.

Paris Climate Convention – A 2015 international agreement where 195 countries committed to limiting global temperature rise and reducing CO₂ emissions.

Peatlands – Waterlogged ecosystems rich in organic matter and carbon; protecting and restoring them helps to store carbon and reduce emissions.

Photosynthesis (enhancement) – The process of increasing CO₂ uptake by promoting plant growth or genetic modification to improve carbon storage.

Polyculture – Growing different types of crops, often among trees, to protect soil, reduce erosion and boost carbon storage.

Renewable energy – Energy from sources like wind, solar and hydro that does not produce greenhouse gases, unlike fossil fuels.

Selective logging – A forestry management practice where only specific trees are harvested, allowing the forest to regenerate and continue storing carbon.

Zero tillage – A farming method that avoids ploughing to reduce soil disturbance, preserve structure and maintain soil carbon stores.