carbon cycle

Question 1

examples of carbon compounds

Answer 1

• carbon dioxide, found in the atmosphere, oceans and soils
• methane, found in the atmosphere, soils, oceans and sedimentary rock
• calcium carbonate, found in calcareous rock (e.g.limestone), oceans, shells and skeletons
• hydrocarbons, fossil fuels in gas and liquid form found in sedimentary rock
• biomolecules, produced by living things, proteins, carbohydrates and fats

Question 2

a systems approach

Answer 2

• global carbon cycle is a closed system, the amount of carbon is constant
• there are local sub systems of the carbon cycle that are open systems
• sub systems characterised by inputs, outputs, stores and transfers
• operates between major carbon stores in organic and inorganic form

Question 3

short term stores of carbon

Answer 3

• terrestrial ecosystems (biosphere), carbon dioxide taken from atmosphere through photosynthesis, carbon is stores organically. Rapid interchange with atmosphere
• atmosphere, carbon is stored as greenhouse gases
• oceanic surface (hydrosphere), rapid exchange with the atmosphere, includes physical and biological processes
• terrestrial soil (pedosphere), microorganisms break most biomass and respire producing carbon dioxide. Amount of time in the store depends n climate

Question 4

flux

Answer 4

the process by which carbon movesbetween stores

Question 5

fast carbon cycle

Answer 5

• rapid transfer of carbon compounds over years, decades and centuries
• involves the transfer of organic carbon via living things taking place between the biosphere, pedosphere and atmosphere
• involves the transfer of inorganic carbon between the ocean and the atmosphere

Question 6

slow carbon cycle

Answer 6

• transfer of carbon compounds over extensive cycles (hundreds of millions of years)
• involves the long term sequestration of the remains of marine creatures and terrestrial forests as fossil deposits of oil, gas and coal
• involves the long term transfers of carbon between the atmosphere and hydrosphere and then the carbon rich sedimentary rocks of the lithosphere. Recycled via tectonic activity

Question 7

key processes in the geological carbon cycle

Answer 7

• mechanical, biological and chemical weathering of rocks
• decomposition of plants and animals
• transportation of ions in rivers to the ocean, where they are deposited
• sedimentation over millennia
• metamorphosis of sedimentary rocks

Question 8

composition of oil and natural gas

Answer 8

• formed from the remains of tiny aquatic animals and plants
• occur in porous rocks, migrating up through the crust until meeting caprocks
• natural gas such as methane is made up of the fractions of oil molecules, so small they are in gas form not liquid, usually found with crude oil

Question 9

composition of coal

Answer 9

-formed from the remains of trees, ferns and other plants
- anthracite is the hardest coal that contains the most carbon so has a higher energy content
- bituminous coals are next in hardness and carbon content
- soft coals such as lignite and brown coal are the major global source of energy supplies but are lower in carbon and emit more carbon dioxide
- peat is the stage before coal and is an important energy source

Question 10

chemical weathering in the geological carbon cycle

Answer 10

• in the atmosphere, water reacts with atmospheric CO2 and carbonic acid forms
• as this is weakly acidic, once the water reaches the surface as rain it reacts with surface minerals, slowly dissolving them into their component ions
• transportation of calcium ions by rivers into oceans
• calcium ions combine with bicarbonate ions in oceans to form calcium carbonate and calcite
• deposition and burial turns the calcite sediment into limestone
• subduction of the sea floor under continental margins by plate tectonics
• some of the carbon rises back up to the surface within heated magma then is ‘deassed’ as CO2 and returned to the atmosphere. Tectonic uplift can also expose previously buried limestone

Question 11

negative feedback regulating the carbon cycle

Answer 11

• increase in volcanic activity
• rise in Co2 emissions and loss of carbon from rocks
• temperature rises
• more uplift of air, condensation and rain
• more chemical weathering and erosion of rocks
• more ions then deposited on ocean floors
• more carbon stored in rocks
• the cycle takes a few hundred thousand years to rebalance

Question 12

volcanic outgassing

Answer 12

• active or passive volcanic zones associated with tectonic late boundaries
• hot springs and geysers at places with no current tectonic activity
• direct emissions from fractures in the earth’s crust

Question 13

how carbon fluxes vary

Answer 13

• diurnally, the fluxes are positive during the day (net carbon movement from the atmosphere to the ecosystem) and negative at night (net movement of carbon from the ecosystem to the atmosphere) as photosynthesis only occurs i the presence of solar energy
• seasonally, in the Northern hemisphere, atmospheric CO2 levels increase in winter as there is less vegetation and growth. In Spring CO2 concentrations drop as plants start growing and photosythesising

Question 14

capacity of soil to store carbon determined by

Answer 14

Climate:
- dictates microbial activity
- rapid decomposition occurs in hot places
- high rainfall means increased potential carbon storage
Soil type:
- clay rich soils have a higher carbon content than sandy soils as clay protects carbon from decomposition
- loss of carbon through cultivation and disturbance

Question 15

Sequestration of Carbon

Answer 15

• Sequestering is the movement of carbon into carbon stores which can lower the amount of carbon dioxide in the atmosphere
• Photosynthesis (by land based plants and phytoplankton) is the main process responsible for sequestering carbon from the atmosphere

Question 16

how is the movement of carbon within oceans is controlled

Answer 16

• Vertically by carbon cycle pumps
• Horizontally by thermohaline circulation

Question 17

ocean sequestration - biological pump

Answer 17

• The biological cycle sequesters carbon in the ocean through photosynthesis by phytoplankton and other marine animals which convert CO2 into organic matter
• This acts as a biological pump transporting carbon from the oceans’ surface to the intermediate and deep ocean stores
• As the biological organisms die, their dead cells, shells and other parts sink into the mid and deep water
• Also, the decay of these organisms releases carbon dioxide into the intermediate and deep water stores

Question 18

ocean sequestration - carbonate pump

Answer 18

• Relies on inorganic carbon sedimentation
• When organisms die and start to sink, many shells dissolve before they reach the ocean floor entering the deep ocean currents
• CO2 absorbed by the oceans from the atmosphere forms carbonic acid which in turn reacts with hydrogen ions to form bicarbonates and then further reactions form carbonates which are stored in the upper ocean
• Some organisms use these carbonates to make their shells or skeletons
• When these organisms die some material sinks to the ocean floor and forms the sea bed sediment store
• Over time, through chemical and physical processes, the carbon is transformed into rocks such as limestone
• This process locks up carbon in the long-term carbon cycle and does not allow an easy return to the ocean surface and so prevents possible venting into the atmosphere as the physical pump does

Question 19

ocean sequestration - physical pump

Answer 19

• Considered the most important transfer
• CO2 is absorbed by the ocean’s surface through diffusion
• Dissolved CO2 is then taken from the surface down to the intermediate and deep ocean stores through downwelling currents
• The thermohaline circulation then distributes the carbon around the planet
• Cold water absorbs more CO2, therefore, as the equatorial waters move toward the poles, more CO2 is absorbed
• Salinity increases at the same time as some of the pure ocean water freezes, making the water denser, therefore, the water sinks (downwelling) taking CO2 from the ocean’s surface to the deep ocean stores
• Allowing more diffusion to occur at the surface and helping to regulate the carbon stored in the atmosphere
  However, there is also the upwelling of carbon from intermediate and deep oceans to the surface oceans
• Through upwelling currents and turbulence created by surface winds, previously stored carbon in the intermediate and deep ocean stores, return to the ocean’s surface and then back into the atmosphere

Question 20

ocean acidification - chemical pathway

Answer 20

• more CO2 added to the atmosphere through human activities such as fossil fuel combustion
• the Co2 us dissolved in seawater, causing the balance of chemical reactions to shift and resulting in more hydrogen ions (increasing acidity)
• more hydrogen ions lead to a lower concentration of carbonate ions which are necessary for shell and skeleton growth for certain marine organisms

Question 21

ocean acidification - chemical pathway

Answer 21

• phytoplankton converts CO2 into organic carbon through photosynthesis
• coastal nutrient runoff from agriculture, rising temperatures and CO2 levels increase amount of phytoplankton
• larger marine organisms consume the plankton and release CO2 through respiration or decomposition, making the ocean more acidic
• upwelling brings the acidic water from the descended decaying organisms to the surface

Question 22

thermohaline circulation

Answer 22

• the global system of surface and deepwater ocean currents driven by temperature and salinity differences between oceans

Question 23

human impact on the carbon cycle

Answer 23

• depleted and enhanced stores
• sped up fluxes
• increased atmospheric carbon, enhancing the greenhouse effect
• sped up carbon release from the slow carbon cycle e.g. extracting hydrocarbon

Question 24

anthropogenic factors affecting the carbon cycle

Answer 24

• burning fossil fuels, releasing greenhouse gases into the atmosphere
• land use change, agriculture releases carbon, machinery and fertilisers, livestock
• deforestation, burning, decreasing carbon store and photosynthesis
• urbanisation, by replacing vegetation and soil and producing cement

Question 25

human impacts, implication for the climate

Answer 25

• on a global and regional scale
• rising global temperature and sea levels
• at a global scale, rising temperatures will lead to more evaporation, meaning more precipitation
• global shifts in weather patterns and more extreme intense and frequent weather events including floods and droughts
• at a regional level, some areas will be hotter and drier, some wetter, and some will have more rain instead of snow
• alterations in ocean temperatures and salinity from global warming will affect thermohaline currents by slowing or reversing the north atlantic drift

Question 26

human impacts, implications for ecosystems

Answer 26

• global warming will have a direct effect on species distribution and habitat change
• affect population sizes and ultimately lead to extinctions
• marine organisms will be affected by lower oxygen levels, rising sea temperatures and ocean acidification
• arctic and coral ecosystems most at risk
• cool, moist regions could provide habitats for additional species as temperatures rise

Question 27

human impacts, implications for the hydrological cycle

Answer 27

• increased evaporation and precipitation and changes in precipitation type
• permafrost will melt releasing a large amount of methane, creating a positive feedback loop
• reduced sea ice, icecaps and glaciers
• direct effect on El Nino

Question 28

the greenhouse effect

Answer 28

• the natural temperature control system of the earth that relies on greenhouse gases
• concentration of atmospheric carbon strongly influences the greenhouse effect
• solar radiation passes through the atmosphere
• 30% reflected by clouds, aerosols and gases in the atmosphere
• 70% absorbed
• 70% of surface absorption re-radiated into space as longwave radiation
• an increase of greehouse gases means more longwave radiation is trapped in the atmosphere, increasing the earth’s temperature

Question 29

energy security

Answer 29

• the uninterrupted availability of energy source at an affordable price
• influenced by availability, accessibility, affordability and reliability
• short term = the ability of the energy system to react promptly to sudden changes in the balance between supply and demand
• long term = timely investments to supply energy in line with economic developments and environmental needs
• required accurate prediction of future energy demands

Question 30

energy mix

Answer 30

• the combination of different available energy sources used to meet a country’s total energy demand
• varies from country to country
• important component of energy security
• balance of domestic sources or imported energy
• balance or non-renewable, recyclable and renewable energy

Question 31

energy pathway

Answer 31

• the route taken by any form of energy from its source to its point of consumption
• involved different forms of transport such as tanker ships, pipelines, electricity transmission grids

Question 32

factors affecting per capita energy consumption

Answer 32

• cost
• physical availability
• climate
• standard of living
• environmental priorities
• technology
• public perceptions
• economic development

Question 33

major energy players

Answer 33

• TNCs, e.g. oil and gas companies, often state owned so are strictly speaking not TNCs, involved in exploring, extracting, transporting, refining and producing petrochemicals
• Organisation of petroleum exporting countries (OPEC), 13 member countries that control around two thirds of the world’s oil reserves. Can control amount and price of oil and gas in the global market. Accused of holding back production to raise prices
• Energy companies, convert primary energy into electricity and then distribute it. Considerable influence setting consumer prices and tariffs
• Consumers, transport, energy and domestic users. Largely passive players in terms of energy prices
• Governments, guardians of energy security, can influence sourcing of energy for geopolitical reasons

Question 34

tar sands

Answer 34

• mixture of clay, sand, water and bitumen
• has to be mined and then injected with steam to make the tar less viscous so it can be pumped out
• biggest areas in Canada and Venezuela
• produce 40% of Canada’s oil output
• extracting bitumen is relatively expensive
• strip mining requires clearance of large areas of Taiga

Question 35

oil shale

Answer 35

• oil bearing rocks that are permeable enough to allow oil to be pumped out directly
• either mined or shale is ignites so that the light oil fractions can be pumped out

Question 36

shale gas

Answer 36

• natural gas trapped in fine-grained sedimentary rocks
• fracking forces out the gas (pumping water and chemicals)
• growing use of fracking means that shale gas provided 25% of US’s gas supply in 2015, increasing US energy security and has an influence of the global oil price
• environmental concerns such as contamination of groundwater and airbourne pollution

Question 37

deepwater oil

Answer 37

• oil and gas that is found well offshore and at considerable oceanic depths
• drilling takes place from ocean rigs
• huge oil deposits found off Brazilian coast in 2006
• concerns about risky nature of drilling in places that aren’t accessible by helicopter and coastal pollution concerns

Question 38

players involved in the harnessing of unconventional fossil fuels

Answer 38

• governments, responsibility to ensure and improve energy security, and most wish to be seen as environmentally conscious. Oil exploration is financially risky, so it being in the private sector appeals to most governments
• exploration companies, financial risks, balance between finding new non-renewable sources and investing in renewables
• environmental groups, aim to publicise the adverse impacts on the environment
• affected communities, balance between positive impacts such as employment and investment and negative impacts such as pollution and disturbance of traditional ways of life

Question 39

recyclable energy

Answer 39

• nuclear energy, as nuclear waste can be reprocessed and reused
• very little CO2 released
• countries with high levels of energy consumption have no option but to use nuclear on top of renewable sources
• safety incidents (Chernobyl and Fukushima)
• security in era of international terrorism
• disposal of highly toxic nuclear waste with a very long half life
• complicated technology hard to access for developing countries
• cost of building and decommissioning

Question 40

effects of deforestation on the carbon cycle

Answer 40

• removes carbon from biosphere and pedosphere
• burning of trees releases carbon into the atmosphere
• removing primary forest and replacing it will grass for cattle reduced biomass (by 40%)
• photosynthesis reduces, lowering amount of carbon absorption from atmosphere
• carbon in soil is washed away by heavy rainfall

Question 41

effects of deforestation on the water cycle

Answer 41

• less interception
• less evaporation and virtually no transpiration
• atmosphere becomes less humid, reducing precipitation
• any evapotranspiration that does occur produces cumulus clouds that rarely produce rainfall
• extreme rainfall events do occur
• rate of runoff increases, leading to greater flood risk
• soil exposed to the sun will dry and erode easily, reducing the quality of the soil and washing into rivers, decreasing water quality and increasing flood risk
• increased local downwind aridity due to the loss of evapotranspiration

Question 42

ecosystem resilience

Answer 42

the level of disturbance that ecosystems can cope with while keeping their original state

Question 43

implications for human wellbeing from forest loss

Answer 43

• essential for human wellbeing through their services
• provision of goods, food, freshwater, wood, fibre, fuel, will affect global economy, nutrition, food security, fuel source, genetic pool (medicine, improving crop strains)
• regulation of Earth systems, water purification, ‘green lungs’, regulates climate, water related risks will increase, ongoing loss of biodiversity
• cultural value, aesthetic, spiritual, educational, recreational, direct reliance by indigenous peoples

Question 44

inter-tropical convergence zone (ITCZ)

Answer 44

• a concentration of warm air that produces rainfall as a part of a global circulation system (The Hadley cell)
• moves north and south over the equator seasonally
• small shifts in its location can cause drought
• more extreme cycles of drought and flood have developed in Amazonia due to shifts in the ITCZ
• this may lead to the forest becoming a net carbon emitter instead of a store

Question 45

sustainable management

Answer 45

the environmentally appropriate, socially beneficial and economically viable use of ecosystems for present and future generations

Question 46

factors affecting the timing of attitudinal change of societies from exploitation to protection of ecosystems

Answer 46

• wealth of countries (environmental Kuznet’s curve)
• rising knowledge of the role the environment plays in human wellbeing
• aid given to poorer nations to help choices over exploitation
• political systems and enforcement of environmental laws
• participation of locals
• power of TNCs

Question 47

arctic barometer

Answer 47

• the idea that the sensitive arctic region provides an early warning system of the pressures and environmental changes caused by global warming

Question 48

Loss of Arctic albedo

Answer 48

• ice is white so reflects most sunlight
• as ice melts, more heat is absorbed by the darker ocean
• replacement of lighter tundra with darker forests as they advance north as temperatures increase also means more absorption of light energy
• this may cause a positive feedback loop

Question 49

drivers of change in energy usage

Answer 49

• rising population
• economic industrial structure, energy needs, technology
• political governance, climate change policy
• cultural and lifestyle, globalisation of consumerism creates more demand for resources

Question 50

IPCC projections

Answer 50

Strong mitigation (2°C future)
- agreed at COP21 by all countries
- mean temperature increases 1.5-2°C by end of century
- arctic likely to have risen by 8°C
Business as usual:
- runaway global warming
- continuing to use fossil fuels as usual
- emissions continue to rise
- rise of 5.6°C by 2100
- more than 15°C rise in the arctic
- large and costly impacts

Question 51

future changes to terrestrial carbon sinks

Answer 51

• increase until 2050, then become saturates and act as sources
• thawing tundra permafrost
• boreal forests shift north
• tropical rainforests - drought

Question 52

future changes to oceanic sink

Answer 52

• increased store in sea grass and algae
• overall reduction as a sink
• warming tropical oceans can’t hold as much CO2
• decreased efficiency of carbon transfers

Question 53

what is mitigation

Answer 53

action to reduce and stabilise GHG emissions and remove them from the atmosphere

Question 54

what is adaptation

Answer 54

action to manage the risks of climate change impacts by adapting to life in a changing climate and adjusting to actual or expected climate

Question 55

carbon capture and storage (CCS)

Answer 55

• capturing the CO2 released by the burning of fossil fuels and burying it deep underground in geological formations
• expensive because complex technology is involved
• no one can be sure that the carbon dioxide will stay underground, it may be gradually leaking into the atmosphere

Question 56

hydrogen fuel cells

Answer 56

• combines hydrogen and oxygen to produce, electricity, heat and water
• will produce energy as long as hydrogen is supplied and will never lose its charge
• promising technology for use as a source of heat and electricity for buildings and a power source for electric vehicles
• hydrogen does not occur naturally as a gas on earth
• can be produced by reforming natural gas or electrolysis (splitting water into hydrogen and oxygen using an electrical current), which could be carbon neutral if renewable energy is used
• hydrogen is high in energy and produces almost no pollution

Question 57

adaptation strategies

Answer 57

• flood risk management
• solar radiation management
• land use planning
• resilient agricultural systems
• water conservation and management
• adaptive capacity of a place will vary dependent on financial or technological resources

Question 58

mitigation strategies

Answer 58

• reduction of energy consumption
• reduction of emissions
• geoengineering
• carbon dioxide removal techniques
• management strategies

Question 59

adaptation, land use planning

Answer 59

• land use zoning and building restrictions on vulnerable flood plains and low lying coasts
• strict runoff controls and soakways
• needs strong governance, enforcement and compensation
• areas at risk such as Bangladesh unfeasible to abandon

Question 60

adaptation, flood risk management

Answer 60

• hard management
• afforestation
• simple changes e.g. permeable tarmac
• management of hard management
• debates over funding sources
• compensation to land owners

Question 61

adaptation, resilient agricultural systems

Answer 61

• more indoor intensive farming
• drought tolerant species
• low tech measures and better practices may generate healthier soils and increase CO2 sequestration e.g. selective irrigation, crop rotation, mulching, covering crops, reduced ploughing, agroforestry
• growing food insecurity adds pressure
• expensive technology and seeds unavailable to subsistence farmers

Question 62

mitigation - reduction of energy consumption

Answer 62

• carbon taxes, emitters to pay a fee
• carbon trading, countries/companies emitting above can buy carbon storage credits from clean developments or reforesting degraded land in other countries
• cap and trade, permits to pollute over a certain level sold on the free market, organisations under can make profits from selling extra permits
• lifestyle changes
• community energy
• local energy production
• fuel efficiency standards for cars and trucks
• efficiency standards for household appliances

Question 63

mitigation, reduction of emissions

Answer 63

• reduce chemical fertiliser
  -reduce intensive livestock farming
• alternative to fossil fuels
  e.g. solar, geothermal, wind, tidal, HEP

Question 64

mitigation, geoengineering

Answer 64

• solar radiation management, releasing atmospheric sulfates on a scale equivalent to a large volcanic eruption or cloud seeding using sea water
• carbon dioxide reduction, development of new technologies to extract GHG from the atmosphere and store them

Question 65

mitigation, carbon dioxide removal techniques

Answer 65

• protecting and enhancing carbon sinks
• using biomass as a fuel source
• using CCS
• enhancing CO2 absorption by the oceans
  e.g. fertilising oceans with nitrogen or increasing upwellings to release nutrients to the surface to increase the biological pump

Question 66

adaptation, solar radiation management

Answer 66

• use orbiting satellites to reflect some inward radiation back into space
• could cool the earth in months and be relatively cheap compared with mitigation
• untried and untested
• may have unintended consequences
• would reduce but not eliminate the worst effects of GHGs e.g. ocean acidification
• would need to continue doing it

Question 67

planned adaptations

Answer 67

• Egypt, sea level rise, installations of hard engineering through National Climate Change Action Plan
• Sudan, drought, expanded traditional rainwater harvesting and water conserving techniques, monitoring deforestation and grazing animals
• Bangladesh, sea level rise and saltwater intrusion, added climate change into National Water Management Plan, flow regulators in coastal embankments, alternative crops and low-tech water filters

Question 68

Rio Earth summit

Answer 68

• 1992
• countries developed a framework to address climate change
• stabilise GHG concentration to a level that would prevent dangerous anthropogenic interference with the climate system

Question 69

Kyoto protocol

Answer 69

• international and intergovernmental meeting in 1997
• stabilisation of GHG emissions by 5%
• countries allocated certain amounts of CO2 to emit
• idea of carbon trading
• alternative energy sources
• included LEDCs into the agreement

Question 70

biofuels

Answer 70

• a fuel derived immediately from living matter
• primary biofuels, unprocessed and used primarily for heating, cooking or electricity generation e.g. fuelwood
• secondary biofuels, derived from processing of biomass and can be used by vehicles and in industrial processes e.g. ethanol derived from sugar cane or oilseed rape