The Carbon Cycle (AQA A Level Geography)

Photosynthesis is the process by which plants use CO₂ from the atmosphere and water in the soil, using energy from sunlight to produce carbohydrates.

True.

Decomposition releases carbon dioxide and methane into the atmosphere.

Sequestration in the context of the carbon cycle is the process where carbon is removed from the atmosphere and stored in liquid or solid form, such as in rocks of the lithosphere or plants of the biosphere.

Carbonation is a form of chemical weathering where atmospheric CO₂ combines with water vapour to produce carbonic acid, which reacts with rocks containing calcium carbonate.

The thermohaline circulation is the global ocean conveyor belt system that distributes heat and carbon around the planet through deep ocean currents.

False.

Oceans absorb more carbon than they emit, with a net gain of 0.6 gigatonnes of carbon (GtC) yr-1.

The biological pump is the process by which photosynthesis by phytoplankton and other marine organisms converts CO₂ into organic matter, transporting carbon from the ocean's surface to deeper waters.

The solubility cycle in oceans is the process by which CO₂ absorbed from the atmosphere forms carbonic acid, which reacts to form bicarbonates and carbonates, some of which organisms use to make shells or skeletons.

False.

While wildfires release stored carbon in vegetation back into the atmosphere, they can also encourage plant growth in the long term, and some plants need wildfires to grow.

Carbon capture and storage (CCS) is the technological process of capturing carbon dioxide (CO₂) from industrial sources, separating it, treating it, and transporting it to a long-term storage location.

The quaternary period is the most recent geological period spanning the last 2.6 million years, characterized by fluctuations between glacial and interglacial periods.

An interglacial period is a warmer phase between ice ages or glacial periods.

False.

Higher temperatures are associated with high concentrations of carbon dioxide in the atmosphere.

Permafrost is permanently frozen ground, typically found in tundra and arctic regions that contains plant material and stores carbon.

A positive feedback loop is a process where the effects of a change amplify the original change, leading to further intensification of the process.

The treeline is the edge of the habitat at which trees are capable of growing, often determined by cold temperatures in tundra regions.

False.

Cold conditions reduce the rate of decomposition due to the decreased effectiveness of decomposers.

A wildfire is an uncontrolled fire that burns in wildland vegetation.

False.

Volcanic activity contributes relatively low amounts of CO₂ (130–380 million tonnes) compared to human activities (30 billion tonnes) annually.

Insolation is incoming solar radiation that reaches Earth's surface.

A hydrocarbon is an organic compound consisting entirely of hydrogen and carbon, often found as fossil fuels such as oil, coal, and natural gas.

In relation to atmospheric CO₂ levels, ppm stands for parts per million, a measure of the concentration of CO₂ in the atmosphere.

True.

Extractive industries are responsible for half of the Earth's carbon emissions.

True.

Undisturbed forestry is carbon neutral, as any decomposition and its slow release of CO₂ are compensated through the growth of new vegetation.

Anthropogenic means originating from human activities or human-made, typically in reference to environmental impacts.

True.

Rice cultivation produces significant amounts of methane due to bacteria in the waterlogged soil of rice fields.

Gas flaring is the burning of natural gas associated with oil extraction when the gas cannot be easily captured and transported.

Globally, the cement industry contributes around 7.5% of total anthropogenic CO₂ emissions.

Agricultural practices indirectly release carbon through burning fossil fuels to run machinery and fertilisers based on fossil fuels.

The percentage of all released carbon due to changes in land use is 10%.

The carbon budget is the amount of carbon stored and transferred within the carbon cycle on a global or local scale, including carbon emissions by various processes against natural or human sequestration.

False.

One GtC is equivalent to a billion (1 000 000 000) tonnes of carbon.

A carbon footprint is the total amount of greenhouse gases produced (directly and indirectly) to support human activities, expressed in gigatonnes of carbon dioxide equivalent per year.

False.

Areas of dense vegetation show increased precipitation rates due to the carbon cycle's effects.

Dimethyl sulphide is a substance that phytoplankton releases into the atmosphere that can increase cloud formation.

An algal bloom is a rapid increase or accumulation in the population of algae in freshwater or marine water systems, often caused by increased levels of nutrients.

True.

Carbon stored in grass provides food for animals in the form of hay, silage, etc.

The natural greenhouse effect is the process by which greenhouse gases in the atmosphere absorb and emit radiation, warming the Earth's lower atmosphere and surface to maintain an average temperature of 14 °C.