Carbon Cycle

Question 1

Photosynthesis

Answer 1

The process whereby plants use the light energy from the sun to produce carbohydrates in the form of glucose. This removes carbon from the atmosphere and allows vegetation to grow

Question 2

Respiration

Answer 2

A chemical process that happens in all cells, which converts glucose into energy. Carbon is released back to the atmosphere but less than is absorbed for photosynthesis meaning that vegetation is naturally a carbon sink.

Question 3

Decomposition

Answer 3

The process where carbon from the bodies of dead organisms is returned to the air as carbon dioxide. Eg microorganisms decompose leaf litter and the carbon is returned to the atmosphere

Question 4

Sequestration

Answer 4

An umbrella term used to describe the long-term storage of carbon in plants, soils, rock formations and oceans

Question 5

Diffusion

Answer 5

The movement of carbon between the ocean and the atmosphere. Cold water can hold more carbon so during glacials there is more diffusion into the ocean.

Question 6

Weathering

Answer 6

The breakdown or decay of rocks in their original place at, or close to, the surface. Chemical weathering involves the absorption of carbon dioxide from the atmosphere, acidic rainwater then reacts with calcium in rocks to form calcium bicarbonate which is then buried and compacted and sequestered in the oceans.

Question 7

Burial and Compaction

Answer 7

Where organic matter becomes buried and is then compressed by the overlying sediment

Question 8

Carbon Budget

Answer 8

A way of using data to describe the amount of carbon that is stored and transferred within the carbon cycle

Question 9

Carbon Sink

Answer 9

Anything that absorbs more carbon than it releases eg the ocean

Question 10

Carbon Source

Answer 10

Anything that releases more carbon than it absorbs

Question 11

Mitigation

Answer 11

Any method used to reduce or prevent emission of greenhouse gases

Question 12

Carbon Capture and Storage (CCS)

Answer 12

The technological ‘capturing’ of carbon emitted from power stations. Atmospheric carbon dioxide is compressed into a liquid and is then pumped and stores several kilometres into the ground.

Question 13

Renewable Energy

Answer 13

Energy generated from sources that can be renewed and used multiple times, eg hydroelectric power.

Question 14

Carbon Farming

Answer 14

Where one type of crop is replaced by another that has greater productivity and can absorb more carbon dioxide from the atmosphere

Question 15

What are hydrocarbons / fossil fuels?

Answer 15

Fossil fuels include coal oil and gas and these are substances made from dead organic matter that has been decomposed and then buried and compacted over millions of years, they store large amount of carbon which is released when they are burnt for energy. 90% of anthropogenic (human) carbon emissions comes from hydrocarbon extraction and burning)

Question 16

Lithosere

Answer 16

A vegetation succession that originates on a bare rocky surface. Bare rock will be colonised by lichens, followed by mosses and grass. Eventually, soil builds up allowing shrubs and trees to grow until climatic climax is reached.

Question 17

Seral Stage

Answer 17

A stage within a sere

Question 18

Sere

Answer 18

A complete vegetation succession

Question 19

Vegetation Succession

Answer 19

The sequence of changes that take place as plant life colonises bare rock, sand, water or salty areas

Question 20

Climatic Climax

Answer 20

The final stage of seral succession. Vegetation remains relatively unchanged unless destroyed by an event such as fire or human interference.

Question 21

Humus

Answer 21

The organic component of soil, formed by the decomposition of leaves and other plant material by soil microorganisms.

Question 22

Milankovitch Cycles

Answer 22

Changes in the shape earth’s orbit and tilt that cause glacial periods and interglacial periods. This is a long-term natural cause of climate change on Earth, it can cause changes to the carbon cycle as cooler oceans absorb more carbon and colder temperatures slow vegetation growth and decomposition.

Question 23

Enhanced Greenhouse Effect

Answer 23

Rising global temperatures due to greenhouse gases being put into the atmosphere because of human activities

Question 24

Combustion

Answer 24

The process where carbon is burned in the presence of oxygen and converted to energy, carbon dioxide and water eg wildfires or burning fossil fuels

Question 25

What is Carbon?

Answer 25

Carbon is an element found in all subsystems of the Earth

Question 26

Why is carbon important?

Answer 26

It is in every living thing It is essential for energy (e.g. fossil fuels) Helps form the basis of the food chain through photosynthesis Crucial in regulating the Earth’s climate

Question 27

Where does carbon come from

Answer 27

Originates from the mantle from when the Earth formed - escaping through plate boundaries and volcanoes

Question 28

How is carbon stored in the lithosphere

Answer 28

The lithosphere is the largest store of carbon, with over 99.9% of all carbon on earth. It is stored in sedimentary rocks and fossil fuels. It is also stored in soils (the pedosphere). It leaves this store through weathering, volcanic eruptions and combustion of fossil fuels.

Question 29

How is carbon stored in the atmosphere

Answer 29

Carbon is stored in the atmosphere as gases such as carbon dioxide and methane. Only about 0.0015% of all carbon on Earth is found in the atmosphere. It leaves this store through weathering, diffusion and photosynthesis.

Question 30

How is carbon stored in the hydrosphere

Answer 30

Carbon is stored in the hydrosphere when it dissolves into rivers, lakes and oceans through diffusion. It is the second largest store with 0.04% of all carbon. The majority is stored in the deep ocean, carbon near the surface regularly exchanges with the atmosphere It leaves this store through diffusion and burial and compaction

Question 31

How is carbon stored in the biosphere

Answer 31

In the biosphere (smallest store) carbon is stored in living things, with approximately 0.0012% of all carbon in this store. Spatially, biospheric carbon is much higher in tropical regions where biodiversity is high. It leaves this store through respiration and decomposition.

Question 32

Seral Succession

Answer 32

Seral succession is the change in species that occur over time as a plant community reaches climatic climax.

Question 33

How is carbon stored in the cryosphere

Answer 33

The cryosphere stores 0.0018% of global carbon, mostly stored in permafrost as decomposing plants and animals become frozen. The carbon is released at methane when the permafrost thaws.

Question 34

Where does lithosere succession take place

Answer 34

Bare rock

Question 35

Stage 1 seral succession

Answer 35

Mosses and lichens colonise bare rock (pioneer species). Over time they weather the rock and decompose to form a thin layer of soil.

Question 36

Stage 2 seral succession

Answer 36

As there is now a thin layer of soil which will contain moisture and nutrients, grasses can start to grow. These will further weather the rock and decompose so the soil layer becomes thicker.

Question 37

Stage 3 seral succession

Answer 37

Shrubs such as heather grow in stage 3, outcompeting the grasses. Plant height increases due to favourable conditions. These shrubs will further weather the rock and decompose so the soil layer becomes thicker

Question 38

Stage 4 seral succession

Answer 38

In stage 4, fast growing soft wood trees such as pine trees grow.

Question 39

Stage 5 seral succession

Answer 39

In stage 5, slow growing hard wood trees such as oak trees grow.

Question 40

What happens if a wildfire burns down a forest

Answer 40

Secondary succession will take place, which means stages 1-5 occur but on an area that has been colonised in the past.

Question 41

What has happened to temperature throughout the Quaternary period

Answer 41

Throughout the Quaternary period (most recent 2.6 million years), temperature has fluctuated in 100,000 year cycles from glacials to interglacials. Glacials last around 100,000 years and interglacials last around 10,000 years.

Question 42

What has happened to atmospheric carbon dioxide levels throughout the Quaternary period

Answer 42

Throughout the Quaternary period carbon dioxide in the atmosphere has fluctuated in 100,000 years cycles, being highest during interglacials and lowest during glacials.

Question 43

Why are atmospheric carbon dioxide levels high during interglacials

Answer 43

During interglacials, carbon dioxide levels are high because warm oceans release carbon, there are more wildfires and there is more decomposition. Rainwater is also warmer so carbon remains in the atmosphere as less is absorbed.

Question 44

Why are atmospheric carbon dioxide levels low during glacials?

Answer 44

During glacials, carbon dioxide levels are low because cold oceans absorb carbon, frozen ground means there is less decomposition and rainwater is

Question 45

Why does temperature fluctuate every 100,000 years

Answer 45

Every 100,000 years the Earth’s orbit around the sun changes from circular to elliptical. During a circular orbit the sun’s energy is even so the planet doesn’t cool down into a glacial, whereas during an elliptical orbit there are times when the Earth is much further from the sun, meaning radiation is lower and ice sheets expand, creating a glacial period.

Question 46

How does volcanic activity affect the carbon cycle

Answer 46

Carbon stored within the Earth in magma is released during volcanic eruptions. The majority enters the atmosphere as CO2. This returns carbon that has been trapped for millions of years in rock deep within the Earth’s crust back to the atmosphere. In the past this will have been a more significant cause of climate change than today.

Question 47

How do wildfires affect the carbon cycle

Answer 47

Wildires rapidly transfer large quantities of carbon from biomass (or soil) to the atmosphere as a result of combustion. As wildfires result in a loss of vegetation in the short term, photosynthesis decreases so less carbon is removed from the atmosphere. In the longer term, however, fires can encourage the growth of new plants. Secondary succession can occur as plants recolonise the area. As succession takes place more carbon will be taken from the atmosphere as a result of photosynthesis. Depending on the amount and type of regrowth, fires can have a neutral effect on the amount of atmospheric carbon.

Question 48

What is the Industrial Revolution

Answer 48

The Industrial Revolution began in 1750 when there was a shift away from farming towards manufacturing, this led to the use of fossil fuels for energy in factories.

Question 49

Greenhouse gas

Answer 49

A greenhouse gas is a gas that absorbs infrared radiation, examples include carbon dioxide and methane

Question 50

Greenhouse effect

Answer 50

The greenhouse effect is when greenhouse gases in the atmosphere trap heat. The light radiation from the sun passes through the atmosphere and is absorbed by the Earth’s surface and turned into infrared radiation. The infrared radiation is remitted but some is trapped by the greenhouse gases, the more that gases there are, the more heat is trapped.

Question 51

How do farming practices affect the carbon cycle

Answer 51

Agricultural activities release carbon dioxide into the atmosphere: o Livestock (mostly cattle) release CO2 and methane when they respire and digest food. This is the largest source of CO2 within agriculture. o Ploughing can release carbon stored in the soil. When soil is turned over, air mixes in and soil microbial activity increases. This results in soil organic matter being broken down more rapidly, and carbon is lost from the soil and transferred into the atmosphere as CO2. o Growing rice in rice paddies releases a lot of methane. This helps accounts for over 40% of agriculture-related greenhouse gas outputs occur in Asia. • As the world’s population has risen, so has food production. As a result, carbon emissions from farming practices have increased. Mechanisation of farming has also increased CO2 emissions as more tractors and other farm vehicles are used across the globe.

Question 52

How has deforestation affected the carbon cycle

Answer 52

Forests may be cleared for agriculture, logging, or to make way for development and urban sprawl. Clearance reduces the size of the carbon store and, if the cleared forest is burned, there is a rapid flow of carbon from the biosphere to the atmosphere. In a natural system, when a tree dies it decomposes very slowly and releases carbon over a long period of time. During that time, new vegetation starts to grow that quickly compensates for the carbon being released by the dead tree (the system is carbon neutral). However, when deforestation by burning occurs, carbon is immediately released into the atmosphere. If the land is then used for farming e.g. cattle ranching, the future absorption of carbon will be reduced. The system has now become a carbon source rather than a sink.

Question 53

How does land use changes affect the carbon cycle

Answer 53

The change of land use from natural or agricultural to urban is a major source of carbon. Urbanisation replaces open countryside with concrete and tarmac. Vegetation is removed, or covered up, to make way for buildings – this reduces carbon storage in the biosphere as there is lower photosynthesis. Globally, urban areas occupy 2% of the total land area. However, these account for 97% of all anthropogenic CO2 emissions. Well over half of the world’s population now lives in urban areas; a proportion that is set to grow over the coming decades. The major sources of these emissions are transport, energy generation, the development of industry, land use conversion from rural to urban and cement production for the building sector. Cement manufacture involves the heating of calcium carbonates (e.g. limestone) producing CO2. It is estimated that cement industry produces 5% of global anthropogenic CO2 emissions

Question 54

How do changes to the carbon cycle affect the land

Answer 54

As more carbon enters the atmosphere, the changes to land include: 1. More photosynthesis for plant water and nutrient availability. 2. Increase in the length of the growing season due to warmer due to limited water availability. However, increases in evapotranspiration limit growth 3. Warming in Tundra regions melting the permafrost, releasing carbon stored into the soil into the atmosphere as CO2 and methane. 4. Increased frequency of wildfires, further increasing atmospheric CO2.

Question 55

How changes in the carbon cycle affect oceans

Answer 55

1. More acidic oceans as the oceans initially absorb more CO2 (ocean uptake). There has been a 30% change in ocean acidity since 1750. This is adversely affecting marine life, including coral reefs. Reef loss is linked to a fall in marine diversity 2. Phytoplankton may not survive at higher temperatures, so numbers may decline. This means less photosynthesis, leaving more CO2 in the atmosphere 3. Sea ice will melt. Arctic sea ice has retreated by 40% in the last 35 years. The loss of sea ice is resulting in a loss of habitat as well as a loss of hunting grounds for larger predators like polar bears 4. Warmer water is less able to absorb CO2, so as temperatures increase the amount of CO2 that can potentially be dissolved in the sea decreases 5. A decrease in salinity in the North Atlantic. Fresh water from melting ice sheets are one cause. This is believed to be leading to a slowing of ocean circulation in the NE Atlantic e.g. the North Atlantic Drift current, which will affect the climate of NW Europe 6. Sea level rise - warmer water has a greater volume due to thermal expansion. It is predicted that oceans will rise between 0.8 and 2m by 2100

Question 56

How do changes to the carbon cycle affect the atmosphere

Answer 56

1. Warmer temperatures leading to more evaporation and therefore, more cloud cover 2. There could be less cloud cover due to reduction in DMS from a reduction in phytoplankton. DMS is released from phytoplankton and acts as a cloud condensation nuclei

Question 57

How does carbon capture and storage (CSS) mitigate climate change

Answer 57

CCS is a technology that can capture up to 90% of carbon emissions produced from the burning of fossil fuels in the atmosphere. CO2 is captured and separated from other gases. It is then compressed and transported by pipeline or ship to a storage location where it is stored deep underground in rocks several kms below the Earth’s surface. Although the technology is proven, some environmental campaigners criticize its cost and the fact that it is linked to increased oil production (CO2 injection during CCS is used to force oil and gas out of rock)

Question 58

How does afforestation and reducing deforestation mitigate climate change

Answer 58

Afforestation and the restoration of degraded forests can increase carbon uptake by the biosphere. Trees act as carbon sinks, removing CO2 through photosynthesis and storing it within their biomass or the soil. Deforestation is a major cause of emissions. A number of countries have started to tackle the issue. Since 2005 Brazil has reduced deforestation by 70%. Sustainable forest management is encouraged e.g. selective logging and replanting and encouraging consumers to buy wood certified by the Forestry Stewardship Council (FSC).

Question 59

How does carbon farming mitigate climate change

Answer 59

This means using farming methods that reduce greenhouse gas emissions and/or capture and hold carbon in vegetation and soils: o Some crops absorb more carbon than others. One type of crop can be replaced by a more productive one that will absorb more CO2 from the atmosphere. o Reduced or no tillage (Ploughing) avoids accelerated decomposition of organic matter and depletion of soil carbon. Crop rotation with pasture or a cover crop increases biomass returned to the soil

Question 60

How does renewable energy mitigate climate change

Answer 60

Governments can reduce reliance on fossil fuels for heating and powering homes by increasing the availability and reducing the cost of renewable energy such as wind, solar and tidal.

Question 61

How do international agreements on emissions mitigate climate change

Answer 61

Countries can work together to reduce emissions. For example, the Paris Agreement (2015) is an international treaty (agreement) to control the total amount of greenhouse gases released. Participating countries agree to keep their emissions within set limits. In reality, the treaties are very hard to enforce, and limits are often exceeded.

Question 62

How do carbon trading schemes mitigate climate change

Answer 62

These are a type of international agreement. Countries and businesses are given a limit on the emissions they can produce. If they produce less they can sell the extra credits, if they produce more they need to buy more credits.

Question 63

How does increasing energy conservation and efficiency mitigate climate change

Answer 63

People can choose to use their cars less and buy more energy efficient cars. Homes and businesses can also be made more energy efficient e.g. with double glazing, insulation and more efficient appliances. Planners can increase the sustainability of developments e.g. by improving public transport and creating more green spaces