Topic 6: The Carbon Cycle and Carbon Insecurity Flashcards
What is the natural carbon cycle
- the movement and storage of carbon between the land, ocean and the atmosphere.
What are the three forms of carbon in the Carbon Cycle?
- inorganic: found in rocks as bicarbonates and carbonates
- organic: found in plant material and living organisms
- gaseous: found as CO2 and CH4 (methane)
Why is carbon important?
It plays a major role in regulating global climate, particularly temperature and the acidity of rain, rivers and oceans.
How is carbon stored?
- Atmosphere - as carbon dioxide and compounds such as methane
- Hydrosphere - as dissolved carbon dioxide
- Lithosphere - as carbonates in limestone and fossil fuels (e.g. coal, oil and gas)
- Biosphere - in living and dead organisms
Three components of carbon cycle:
- Stores - where carbon is held, e.g. atmosphere or lithosphere
- Fluxes (transfers) - the flows which move carbon between stores (from one sphere to another) measured in petagrams or gigatonnes of carbon per year. e.g. photosynthesis and respiration.
- Processes - the physical mechanisms which drive the fluxes between stores e.g. photosynthesis and diffusion
What is the geological carbon store?
- natural cycle that moves carbon between land, oceans and atmosphere.
- involves a number of chemical reactions that create new stores which trap carbon for significant periods of time.
- tends to be a natural balance between carbon production and absoption. However there can be occasional disruptions and short periods before balance is restored, e.g. major volcanic eruptions emitting large quantities of carbon.
Process of geological carbon cycle:
- terrestrial carbon, held within mantle, is released into the atmosphere as CO2 when volcanoes erupt. This is known as out-gassing.
- CO2 within the atmosphere combines with rainfall to produce carbonic acid that dissolves carbon-rich rocks, releasing bicarbonates. This is chemical weathering.
- rivers transport weathered carbon and calcium sediments to the oceans, where they are deposited.
- carbon in organic matter from plants and animal shells and skeletons sinks to the ocean bed when they die, building up strata of coal, chalk and limestone.
- carbon-rich rocks are subducted along plate boundaries and eventually emerge again when volcanoes erupt.
- the presence of intense heating along subduction plate boundaries metamorphoses sedimentary rock by baking, creating metamorphic rocks. CO2 is released by the metamorphism of rocks rich in carbonates during this process.
geological stores of carbon - out-gassing:
- The Earth’s crust contains pockets of carbon dioxide which can be disturbed by volcanic eruptions or seismic activity
- This release of gas that has been dissolved, trapped, frozen or absorbed in rock is called outgassing
- Outgassing happens at:
+ Volcanic zones associated with plate boundaries (including subduction zones and spreading ridges)
+ Areas with no current volcanic activity, e.g., the geysers in Yellowstone National Park, USA
+Direct emissions from fractures in the Earth’s crust - The gas released by volcanic eruptions is relatively insignificant in comparison to human activity
+ Volcanoes currently emit 0-15 - 0.26 Gt carbon dioxide annually
+ Fossil Fuel use emits about 35 Gt
geological stores of carbon - chemical weathering:
- chemical weathering water reacts with carbon dioxide in the atmosphere forming carbonic acid, which reaches the surface as rain dissolving surface minerals.
- rivers transport calcium ions from the land to oceans which combine with bicarbonate ions to form calcium carbonate
- deposition and burial turns the calcite sediment into limestone.
- subduction of the sea floor (tectonic uplift can expose buried limestone)
- some carbon rises back to the surface within magma which is returned to the atmosphere as carbon dioxide.
What are the four key processes involved in the bio-geochemical carbon cycle?
- photosynthesis: removing CO2 from the atmosphere to promote plant growth.
- respiration: releasing CO2 into the atmosphere as animals consume plant growth and breathe.
- decomposition: breaking down organic matter and releasing CO2 into the atmosphere.
- combustion of biomass and fossil fuels - releasing CO2 and other greenhouse gases into the atmosphere.
Variations in fluxes - fast and slow:
- ## if it’s too dark, hot or cold, and low levels of CO2 the speed of the cycle reduces.
Variations in fluxes - geographical patterns:
- levels are always higher in the Northern hemisphere as it contains greater landmasses and greater temperature variations than in the Southern Hemisphere.
What is carbon sequestration?
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
What is ocean sequestration?
- 93% of carbon dioxide is stored in undersea algae, plants, coral and dissolved form, making oceans the largest carbon store on Earth
- The movement of carbon within oceans is controlled:
+Vertically by carbon cycle pumps
+Horizontally by thermohaline circulation - There are three carbon cycle pumps which move carbon dioxide to the sea floor and to the ocean surface to be released into the atmosphere
Ocean sequestration - biological pump:
- The biological cycle sequesters carbon in the ocean through photosynthesis by phytoplankton and other marine animals which converts CO2 into organic matter (10GtC per year)
- This acts as a biological pump transporting carbon from the oceans’ surface to the intermediate and deep ocean stores (10 GtC per year)
- 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
- Oceans regulate the composition of the atmosphere by moving carbon from the ocean’s surface (where it may vent back into the atmosphere) and storing it in the mid and deep ocean store, along with the dissolved carbon store, which regulates the carbon cycle
Ocean sequestration - carbonate pump:
- Relies on inorganic carbon sedimentation
- When organisms die and starts to sink, many shells dissolve before they reach the ocean floor entering the deep ocean currents
- The solubility cycle occurs when 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 (1750 GtC)
- 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.
Ocean sequestration - physical pump:
- Considered the most important transfer
- Carbon dioxide (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 (96 GtC per year)
- 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, 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 (105.6 GtC yr-1)
- 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
The role of trees - carbon sequestration:
- 95% of a tree’s biomass is made up from the CO2 that it sequesters and converts into cellulose.
- carbon fixation turns gaseous carbon - CO2 - into living organic compounds that grow.
- the amount of carbon stored within a tree, woodland or forest depends on the balance between photosynthesis and respiration.
Mangroves and the role of soil:
- mangroves are vital processors - sequestering almost 1.5 metric tonnes of carbon per hectare per year.
- their soils are anaerobic and due to this the decomposition of plant matter is slow. As a result, little of the carbon can be respired back to the atmosphere and the store remains intact.
- however if mangroves are drained or cleared, carbon is released into the atmosphere. Mangroves are being closed for tourism. Even 2% is cleared results in carbon released being 50 times the natural sequestration rate.
Tundra soils - carbon sequestration:
- much of soil in the tundra is permanently frozen and contains ancient carbon.
- this locks any carbon into an icy store due to the decayed organic matter being frozen.
- tundra soils contain carbon that has been trapped for hundreds of thousands of years.
Tropical rainforests as carbon stores:
- tropical rainforests are huge carbon sinks, but are fragile and can quickly disappear.
- carbon within rainforests is mainly stored in trees, plant litter and dead wood.
- as litter and dead wood decay they are recycled so quickly a soil store does not develop.
- TR absorb more atmospheric CO2 than any other terrestrial biome, accounting for 30% of global net primary production, although they cover 17% of the earth’s surface.
- if they died off the world would lose a massive carbon sink.
What is the natural greenhouse effect:
- solar energy is received from the sun, fark surfaces on Earth absorb this sunlight and some is reflected back into space.
- the greenhouse gases in the atmosphere act like a ‘blanket’ to trap some of the heat and keep the earth warm (without them we would be 16 degrees Celsius). This means life on earth is sustained.
- CO2 is the most common greenhouse has and it has the highest radioactive forcing effect (RFE) - holds onto heat for longer.
Enhanced greenhouse effect:
-concentration of greenhouse gases such as CO2 and CH4 in the atmosphere have increased 25% since 1750. 75% of CO2 emissions have come from burning fossil fuels.
- many believe that this is the cause of increased global temperatures and leading to enhanced greenhouse effect.
- human activities, e.g. burning fossil fuels and deforestation release natural carbon stores and nitrogen, which then combine with oxygen to form greenhouse gases. e.g. carbon combines with oxygen to form CO2.
- level of water vapour increases as well as global temperatures. Higher temps results in greater evaporation of water leading to greater condensation. This causes increased cloud cover, trapping heat in the atmosphere.
enhanced greenhouse effect - temperature:
- due to the angle of the sun’s rays solar insolation is intense at the Equator, but dispersed over a wider area at the Poles.
- different characteristics of the Earth’s surface (e.g. whether it is light or dark) also affect how much heat is absorbed or reflected (albedo) snow reflects heat and dark forests absorb it.
- heat is redistributed around the globe by air movement, caused by both pressure differences and ocean currents.
enhanced greenhouse effect - distribution of precipitation:
- solar radiation (insolation) is most intense over the Equator, convection and low-pressure systems dominate there. Rainfall is high all year round.
- as the air pressure rises around 30 degrees north and south of the Equator, precipitation decreases. Clouds rarely form there.
- mid latitudes: air masses of different characteristics meet, and low-pressure systems bring rainfall.
- nearer the Poles, precipitation falls as the air cools further ad us dense and dry - creating polar deserts.
How does photosynthesis regulate the composition of the atmosphere?
- phytoplankton in the oceans sequester CO2 through the process of photosynthesis - pumping it out of the atmosphere and into the ocean store.
- terrestrial photosynthesis enables plants to sequester 100-120Gt of CO2 each year. This is then released back into the atmosphere through respiration and decomposition.
Ocean and terrestrial photosynthesis:
- The carbon cycle is dependent on ocean and terrestrial photosynthesis in regulating the composition of the atmosphere
- Plants photosynthesising play a vital role in helping to keep carbon dioxide levels relatively constant thus helping to regulate average global temperatures
- As a result, patterns in plant productivity and carbon density are evident
- Highest productivity NPP occurs either in warm and wet regions such as the tropical rainforest or in shallow ocean waters
Soil and carbon:
- carbon is vital in soils. It supports micro-organisms that maintain the nutrient cycle, break down organic matter, provide pore spaces for infiltration and storage of water, and enhance plant growth.
- without carbon, the nutrient and water cycles cannot operate properly.
Characteristics of healthy soils:
- dark and porous
- sequester carbon
- retain moisture, which regulates soil temperature during heatwaves ad reduces the effects of drought.
- improve resilience to wetter weather, as they enable infiltration and percolation of water (reducing soil erosion and flood risk)
Fossil fuel combustion - balance?
- earth’s carbon reservoirs act as sources (adding carbon to the atmosphere) and sinks (removing it). If the sources are equal they will be in equilibrium. This helps to stabilise global temperatures.
- however, human activities (e.g. deforestation and fossil fuel combustion) have increased CO2 inputs into the atmosphere, without any increases in the natural sinks (e.g. oceans or forests).
- process of fossil fuel combustion has altered the balance of carbon pathways and stores - with carbon being released in large amounts.
Fossil fuel combustion - implications for climate?
rising levels of CO2 are leading to increased global temperatures. However the increases will vary.
- Across Europe, annual average land temperatures are predicted to increase by more than the global average. The largest increases are expected to be over Eastern Europe in winter, and southern Europe in summer.
- extreme weather events are also likely to increase in both intensity and frequency.
- annual precipitation is projects un increase in N Europe and decrease in S Europe - increasing the differences between regions that are currently wet and those which are dry.
Fossil fuel combustion - arctic amplification?
- arctic region is warming twice as fast as the global average.
- melting permafrost releases CO2 and CH4, increasing the concentration of these greenhouse gases in the atmosphere leading to increased global temperatures and further melting.
- rapid warming has led to extensive melting of ice in summer months and greatly reduced snow cover and reduction in permafrost.
- shrubs and trees, previously unable to survive i tundra, have started to establish themselves.
Fossil fuel combustion - implications for ecosystems:
- Ecosystems help regulate carbon and hydrological cycles as well as providing goods and services for humans and the planet
- Already, species with low population numbers, limited climatic ranges or restricted habitats are at risk
- Marine ecosystems are threatened by lower oxygen levels, higher rates of ocean acidification and food chain changes (resulting from rising temperatures)
- Coastal ecosystems are at risk from sea level rise
- Although most species will be impacted negatively, there are some that may benefit. E.g. cool, moist regions (e.g., UK) could provide habitats for more species
Fossil fuel combustion - implications for the hydrological cycle?
- precipitation in the form of snow could diminish and rainfall patterns change.
- river discharge patterns may also change, with greater flooding in winter and drought in summer.
- as Alpine glaciers melt, water flows lead to increased sediment yield. Once the glaciers have retreated, discharge and sediment yields fall and water quality declines.
What are carbon pathways?
- in theory, constant levels of CO2 in atmosphere are maintained if photosynthesis keeps up with the release of GHGs.
- increased thawing has accelerated the process of carbon release. Increased thawing means that methane and water are also being released as ancient vegetation decomposes and trapped gases seep to the surface. Plants and micro-organisms grow faster than before and respire CO2.
What are the two types of carbon pathways?
- pathway 1: shrubs and trees invade the Arctic landscape and store more carbon than is being released into the atmosphere. A short-term balance is reached - i.e. negative feedback.
- pathway 2: the decomposition of plant material in wet soils reduces carbon stores by releasing more CO2 and CH4 into the atmosphere. Increased greenhouse gases reinforce global warming in the longer term - i.e. positive feedback. Scientists believe that this will add as much carbon to the atmosphere each year as all f the land use changes in the rest of the world combined.
Madagascan + USA comparison - energy usage:
- Madagascar has a population of 23 million and uses little energy
- Manhattan (USA) has a population of 1.7 million yet consumes more energy in a year than an average Madagascan will in a lifetime.
Urban consumption - UK:
- cities consume 75% of world’s energy and produce 80% of its greenhouse gas emissions.
- e.g. City of London generates 1.7 million tonnes of carbon per year and its resident population averaging 1.8 tonnes of carbon per capita.
- London’s demands are met through a web of national and international supply lines, and involve several key players.
Rural consumption - Peru:
- national program of solar-panel installation made electricity available to 500,000 villages across Peru from 2006-2015.
- provides increased productivity allowing extra processing of cereals, meat, wood and cocoa. This helps to boost incomes and raise rural standards.
- increasing energy consumption is helping to bring sustainable development and a brighter future for Peru’s villagers.
Energy security definition:
- being able to access reliable and affordable sources of energy. These may be domestic, but could also include energy sources from ‘friendly’ countries
What are primary and secondary sources?
- primary: consumed in their raw form. They include burning fossil fuels, nuclear energy, and renewable sources. They can also be used to generate electricity.
- secondary sources: electricity - flows through power lines and infrastructure to power homes and businesses.
Domestic and overseas sources:
- UK consumed less energy in 2015 than in 1998 despite population growth.
- more energy came from renewable sources
- however, declining domestic North Sea oil and gas have made the UK more reliant on imported energy.
- now the country imports more than it produces domestically and therefore has an energy deficit and is energy insecure.
Renewable sources:
- e.g. solar, wind and wave power.
- these are continuous flows of nature, which can constantly be reused.
non-renewable sources:
- e.g. coal, oil and gas. Exploitation and use of these stocks will eventually lead to their exhaustion.
- traditionally coal has been the major source for producing electricity.
recyclable sources:
- e.g. reprocessed uranium and plutonium from nuclear power plants and heat recovery systems.
Factors affecting energy consumption:
- physical availability
- cost
- technology
- political considerations
- level of economic development
- environmental priorities
Physical availability - UK:
- until 1970s: UK relied heavily on domestic coal from Yorkshire, Derbyshire, South Wales and north-east England.
- also among global leaders in nuclear technology from the 1950s-70s, but lost momentum after discovery of large reserves of North Sea oil and gas which greatly altered the UK’s energy mix.
Physical availability - Norway:
- mountainous, with steep valleys and plentiful rainfall, HEP is a natural energy choice.
- much of Norway’s oil and natural gas is exported (e.g. to the UK)
- coal from Svalbard is also exported.
Cost - UK:
- North Sea oil is expensive to extract, so if global prices fall (like in 1997-98), it becomes less viable.
- stocks pf North Sea oil are also declining, which is forcing the UK to import more.
Cost - Norway:
- Norsk Hydro runs over 600 HEP sites, supplies 97.5% of Norway’s renewable sources.
- HEP costs are low once capital investment is complete.
- however, transfer of electricity from HEP production in remote regions to urban population centres and isolated areas is expensive.
Technology - UK:
- current technology and environmental policy make the extraction and use of oil unrealistic and expensive.
- last deep mine closed in 2015, although 80% of of UK’s primary energy still came from fossil fuels.
- technology exists for ‘clean coal’ but coal has lost its political support.
Technology - Norway:
- deepwater drilling technology enabled both Norway and the UK to develop North Sea oil and gas extraction.
Political considerations - UK:
- public concern is growing over new and proposed fracking and nuclear sites
- privatisation of UK’s energy supply industry in the 80s now means overseas companies (French EDF) decide which energy sources are used to meet UK’s demand.
Political considerations - Norway:
- HEP been used since 1907 and Norwegian Water and Energy Directorate manages the nation’s power supply.
- Norwegian government has an interventionist approach, which prevents foreign companies from owning any primary energy source sites - waterfalls, mines, forests.
- royalties and taxes are paid into the government to boost the standard of living through govt spending but profits also go to a sovereign wealth fund to prepare for a future without fossil fuels.
Level of economic development - UK:
- GDP per capita: $41,200 (2015)
- Energy use per capita: 2752kg oil equivalent (2014)
- Average annual household energy costs: £1300 (2015)
Level of economic development - Norway:
- GDP per capita: $61,500 (2015)
- Energy use per capita: 5854kg oil equivalent (2014)
- Average annual household energy costs: £2400 (2015)
Environmental priorities - UK:
-2015: committed to a 40% reduction in domestic greenhouse gas emissions by 2030, compared to 1990 levels.
- intends to broaden its energy mix with renewable sources (especially wind) and more nuclear power.
- however, in 2015, it abandoned its ‘Green Deal’ conservation and insulation schemes.
Environmental policies - Norway:
- 2015: committed to a 40% reduction in domestic greenhouse gas emissions by 2030, compared to 1990 levels.
- Norway’s ‘Policy for Change’ was launched in 2016, with a domestic target of being carbon neutral by 2050.
Changes in energy mix (UK) from 1980 - 2012:
- nuclear power: 6% - 9%
- renewables: remained the same at 2%
- coal: 34% - 15%
- gas: 19% - 40%
- oil: 38% - 32.5%
- biomass and waste: remained the same at 1%
- hydropower: 2% - 1%
Changes in energy mix (Norway) from 1970 - 2010:
- renewables: <1% to <0.5%
- coal: 6.5% - <1.5%
- gas: 2010 - 20%
- oil: 51% - 33.5%
- biomass and waste: 2010 - 5%
- hydropower: 42.5% - 40%
Energy pathway definition:
- term used to describe the flow of energy between a producer and a consumer, and how it reaches the consumer, e.g. pipeline, transmission lines, ship, rail.
What are examples of energy players:
- Energy TNCs
- OPEC
- National governments
- Consumers
Role of energy TNCs:
- TNCs explore, exploit and distribute energy resources
- own supply lines and invest in distribution and processing of raw materials, as well as electricity production and transmission.
- they respond to market conditions yo secure profits for their shareholders.
Examples of energy TNCs:
- Old players: BP (UK) and Shell (UK-Netherlands); Exxon/Mobil (USA)
- New players: Petrobas (Brazil), Reliance (India) and Gazprom (Russia)
What is OPEC?
- The Organisation of Petroleum Exporting Countries - permanent inter-governmental organisation (IGO)
- between them, OPEC producers control 81% of proven world oil reserves.
Role of OPEC:
- mission is to co-ordinate and unify petroleum policies of its members, to ensure the stabilisation of oil markets.
- this is to ensure steady income for producers and efficient, economic and regular supply of petroleum to consumers.
Role of national governments:
- to meet international obligations, whilst securing energy supplies for nation’s present and future, as well as supporting nation’s economic growth.
- regulating the role of private companies and setting environmental priorities.
Examples - national governments:
- EDF (France) and China General Nuclear are two government-backed energy TNCs involved in developing new nuclear power plants in the UK.
- EU governments aim to fulfil CO2 emissions targets and reduce fossil fuel dependency.
Role and factors affecting consumer attitudes:
- Create demand. Purchasing choices are often based on price/cost issues, e.g. petrol prices can be keenly competitive between supermarkets.
What is the location of fossil fuels?
- not evenly distributed throughout the world and are determined by underlying geology.
Geology - coal:
- most coal in Western Europe and North America was formed during the Carboniferous period (300-360 million years).
- successive layers of rainforest-type tress within swamp forests accumulated as they feel, and were transformed under pressure of over-lying strata into seams of coal.
Geology - oil and gas:
- generally younger than coal and were formed during the Mesozoic era (250-260 million years ago)
- formed from fossil remains of plants and animals that dies and buried under alternate layers of mud.
- heat and pressure converted these fossil remains into oil and natural gas., with accumulated into porous sandstone.
Energy pathways - ESPO:
- East Siberia Pacific Ocean
- 4188km long ESPO pipeline exports crude oil from Russia to China, South Korea ad Japan.
- built by Russian energy company Transneft, and was completed in 2012.
What are other examples of pipelines?
- Yamal-Europe pipeline
- Keystone XL oil and Rockies Express
- Transmed
- West-East Gas Pipeline Project (WEPP)
- Kazakhstan-China
What is the Yamal-Europe pipeline (Nordstream)?
- a 4107km gas pipeline that runs from Russia through Belarus and Poland into Germany.