Carbon Cycle


Carbon Cycle - Geological

The Geological Carbon cycle transfers carbon between the Lithosphere, Hydrosphere and Atmosphere. It considered to be relatively slow but balanced, with carbon production and absorption being in equilibrium; sometimes there are disruptions that temporarily delay the restoration of equilibrium such as major volcanic eruptions. Processes include:

1.)  Out gassing from volcanic eruptions releases CO2 into the atmosphere

2.) Chemical weathering through carbonic acid rain is caused by increased CO2 concentration and dissolvese carbon-rich rocks

3.) River transports sediment containing carbon

4.) Sediment layers form on the sea bed

5.) During subduction sediment is broken down to form carbon-rich metamorphic rock to be released during volcanic eruptions in magma. 

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Carbon Cycle - Biological, Terrestrial

The terrestrial carbon cycle comes from the transfer of carbon through primary producers, consumers and decomposers. It balances the Carbon Cycle to a much greater scale, transfering ~120 Gt annually between the Atmosphere and Biosphere.

Carbon is sequestered into the soil during photo-synthesis but is mainly released through respiration and decomposition to the atmosphere. Certain ecosystems, such as tropical rainforests or coral reefs sequester more carbon, whilst deserts sequester less carbon due to low vegetation. The amount of carbon sequestered to produce biomass is compared through Primary Productivity; more specifically, Net Primary Productivity is the amount of biomass produced minus the energy lost through respiration, in Rainforests this is ~ 2200 g/m^2 whilst Tundra are only ~100g/m^2.

Micro-organisms transfer cabron between the soil store and the atmosphere through decomposition and respiration. They provide essential nutrients for vegetation growth and fluxes within the Water Cycle. In colder climates and season, the level of decomposition is less, therefore releasing less CO2. In contrast, during warmer climates, more carbon is used in photosythesis and decomposition, balancing the atmosphere annually.

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Carbon Cycle - Biological, Oceanic

The biological carbon cycle transfers carbon between the atmosphere and hydrosphere. It consists of two main "pumps"/systems that sequester carbon; on average the it transfer 90 Gt annually.

The biological carbon pump sequesters carbon into the ocean through phytoplankton photo-synthesis. Chemical conversion in the poles then breaks down carbon; this has increased due to increased algae growth at the poles. Through the food chain, it sinks into the deep ocean as dead organisms. Seaweed farming can also be used to increase the rate of carbon sequestration, as well as the use of alkaline chemicals to break down carbon further

The physical pump consists of the Thermohaline Circulation in which carbon is transported to the poles through convection currents to be broken down and stored. During this process, it is also released back into the atmosphere as warm air rises through upwelling. 

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Balancing the Carbon Cycle Part 1

Energy from the sun is absorbed by the earth's surfaced and trapped by greenhouse gases in the atmosphere. CO2 is the most common greenhouse gas, however since 1850 there has also been a 250% increase in Methane, which is 21x more powerful than CO2.

This has led the Enchanced Greenhouse Effect, caused by the burning of fossil fuels and contributing to 75% of CO2 emissions since the 1980s. Other human activities such as deforestation release carbon into the atmosphere, increasing global temperatures and levels of evaporation, which can impact climatic variability and precipitation patterns.

Solar Insolation is the intensity of solar radiation over a given area on the Earth's surface. It is most intense at the Equator and more dispersed at the poles. Other physical factors such as albedo (the light/dark surfaces of the Earth e.g snow reflecting heat) contribute to the distribution of heat and thereby air and ocean currents globally.

Moisture content in the air is controlled by the heating of the Earth's surface and atmosphere. Warm air rises and condenses into clouds containing water vapour along the Equator, resulting in high precipitation. In contrast, areas of high pressure, such as the poles, have low precipitation.

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Balancing the Carbon Cycle Part 2

Fossil Fuels are long-term stores within the Lithosphere that have existed for 70-100 million years. The burning of fossil fuels has increased the emission of CO2 without providing a counterbalancing carbon sink. As a result, the balance of carbon pathways/fluxes entering the atmosphere has been dramatically disrupted since the 1950s.

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Energy Players

OPEC: The Organisation of the Petroleum Exporting Countries controls 80% of the World's proven oil reserves and controls the price of oil by manipulating supply and demand of oil exports. Their aim was to ensure energy security for consumers as well as create a stable oil market for investors. However, since 2012-2016, OPEC has had to drastically lower oil prices in order to compete with the US's increased oil production through fracking.

TNCs: TNCs, such as Russian Gazprom and PetroChina, don't control oil reserves but instead invest in the distribution and transport of oil through supply lines and power grids (after it has been converted into electricity). TNC's main aims are to maximise profits.

Governments: Goverments aim to provide energy security for current and future generations. They regulate TNCs, such as EDF, to ensure that CO2 emission targets are met (e.g via construction of Nuclear plants; however limited as ultimately investment is up to TNC)

Consumers: Consumers want energy for the cheapest price and create demand. They can protest against energy issues such as fracking or nuclear energy and can also be incentivised to consider more sustainable methods e.g solar panels or electric cars.

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Energy Security and Mix

Energy Security is defined as the access to an affordable supply of energy resources.

Primary Energy refers to natural resources that can be changed into energy whilst Secondary Energy refers to the process of generating electricity through natural processes.

An Energy Mix is the combination of available energy sources to meet demands. This usually includes Primary and Secondary energy, as well as domestic and overseas sources.

Their is a global trend to support the claim that there is a correlation between GDP per Capita and energy consumption. Furthermore, declining domestic oil and gas reserves within the North Sea haveled to the net import of energy within the UK doubling between 1999-2019, changing from a net exporter to a net importer. This has left the UK in an energy deficit in which they are energy insecure and dependent on countries with energy surplus, such as Russia. 

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Energy Consumption

Factors that affect Energy Consumption:

  • Physical Availability: The UK was dependent on domestic coal until the 1970s, after which they saught increased usage from the North Sea.
  • Cost: HEP in Norway supplies 98% of it's renewable energy. It is a low initial investment however distribution can be costly.
  • Technology: Deepwater drillling has facilitated the extract of previously inaccessible oil and gas in the North Sea.
  • Politic Considerations: Privatisation of UK energy supplies means France's EDF decides which energy resources it uses. Alternatively, the Norwegian government prevents TNCs from owning primary energy sources such as waterfall, mines or forests. Furthermore, ~1.5% of profits are diverted into a sustainable wealth fund to plan for future investments without fossil fuels.
  • Level of Economic Development: GDP per capita is directly correlated to energy consumption. In Norway, $60,000 = 6 tonnes of oil anually.
  • Environmental Priorities: The UK is broadening it's energy mix with renewable sources and nuclear powe. Their CO2 emissions are down from 10 tonnes per capita (1980) to 7 tonnes (2015) per capita annually.
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Energy Pathways

Energy Pathways are the flow of energy between producers and consumers, e.g pipelines, or transmission lines such as the national grid. However, the distribution of energy is often dependent on bilateral (two) and multilateral (many) agreements between countries. These are referred to as transit states by the producer and are obstacles to reaching the consumer.

For example, Russia's Gazprom is a natural gas pipeline that exports 80% of Russia's gas to Europe. Due to Russia's tense relationship with Europe, it minimises it's interaction with transit states who may risk affecting the price or security of energy. Furthermore, the Nord Stream pipeline runs under the Black Sea to Bulgaria, thereby avoiding taxation laws from transit states and minimising the threat of security through war or terrorism.

In contrast, sea channels can be easily disrupted at key convergence points within the transport routes called chokepoints. For example, 20% of the world's oil supply passes through the Strait of Hormuz in the Middle East. Disruptions to pathways include: A winter storm in 2013 that damaged a UK import pipeline; Transnational pipelines in Nigeria were bombed in 2016 losing 300,000 barrels of oil daily; Piracy in the Strait of Malacca; The Syrian conflict is focused around the construction of oil pipelines through Syria to Russia, leading to a proxy war between the USA and Russia.

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Fossil Fuels

Fossil fuels still make up for 86% of the global energy mix and countries such as Russia, USA and the Middle East have the largest fossil fuel reserves which they export (100-300 barrels a day). As a result, global consumption of fossil fuels has increased by 50% since 1990s, predominatedly due to the rapic economic growth of China's middle class. 

Unconventional fossil fuels include: Deep water oil, Tar Sands, Shale Gas, Oil Shale. Canadian Tar sands offers energy security for Canada and the USA, potentially meeting 15% of NA's needs by 2030. However, it is much more expensive to extract and is extremely damaging to the environment (high carbon emissions, destruction of forests and peat bogs).

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Renewable alternatives to Fossil Fuels

The UK's fossil fuel consumption is decreasing with wind energy accounting for an estimated 25% of the UK's electricity in 2020 and solar power doubling between 2014-2015. 

Large scale projects such as the construction of the new Hinkley Point Nuclear Plant in partnership with EDF began in 2016 and aimed to supply 7% of the UK's electricity by 2026. However, there are several problems. The initial cost was £18 billion and the current agreed Strike Price (minimum selling price) between EDF and the government was £92.50/MwH. This makes it more expensive than other renewable sources such as Solar and Onshore/Offshore Wind (£50-80/MwH and £80-120/MwH respectively) but could provide a reliable source for the next 60 years. Furthermore, there are protests from the local communities regarding the safety of nuclear energy. While examples of nuclear failure are few, they include major catastrophes such as Chernobyl or Fukushima; before 2011 Japan used nuclear power to supply 27% of it's energy but was forced to import more following the Tohoku tsunami, they have since begun reintroducing nuclear power.

Other renewable energy projects in the UK include:

  • Swansea Bay Tidal Lagoon - 16 tidal turbines for 150,000 homes
  • Walney wind turbine projects - 660 MW generated and 10% of wind energy supplier for UK
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Radical Technology and Biofuels

Brazil began the production of biofuel from sugar cane in the 1970s. Bio-ethanol is an alternative to petrol that emits 80% less CO2 and has reduced total emissions by 350 million tonnes since 2003. Within Brazil bio-ethanol is widely available with it being law that it must account for a minimum of 25% of the petrol mix within gas stations. However, due to recent inflation, petrol prices have decreased to become more competitive globally, thereby reducing the incentive to buy biofuel. Furthermore, there are long-term impacts from clearing land to grow biofuel farm such as eutrophication and a loss of carbon sink.

Carbon Capture and Storage (CCS) is a promising radical technology that stores and compresses CO2 emitted during the coal-firing process into underground, geological resevoirs such as aquifers. Theoretically this could lead to up to 20% of global emissions being cut, however it is not currently financially viable, meaning it could take decades to effectively implement, thereby putting pressure on renewable sources to decrease CO2 emissions.

Hydrogen fuel cells are an alternative to oil. THey convert hydrogen into electricity, producing water a s a by-product. These fuel cells are highly energy efficient compared to petrol engines. However, the current scale of the project is limited as investing in distribution and storage for the mass-market would become costly, compared to the competitively low price of petroleum which attracts governments. Similiarly, increased energy efficiency technology such as Smart Meters, LED light bulbs and electric cars could be commonplace methods of reducing CO2 emissions, however they are not widely available, especially in developing countries.

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*Threats to the Water and Carbon Cycle

Increased global temperatures through solar insolation can affect precipitation patterns by increasing evaporation rates and releasing more water vapour (a greenhouse gas) into the atmosphere. A change in moisutre content within the air can then contribute to water insecurity. Climatologists predict that existing patterns will strengthen, leading to extreme weather events, such as droughts or floods, beccoming more common and intense.

For example, the Amazon Basin has suffered extreme droughts in 2005, 2010 and 2015. The large tropical forest plays a key role in the Eath's carbon cycle, holding 17% of the terrestrial carbon store. However, following the 2010 drought, the bason experienced increased tree mortality and forest fires that released CO2 and prevented the Amazon's ability to regenerate as a carbon sink.

Additionally, rising temperatures are expected to cause increased snowmelt, such as within the Western Alpines (expected to be ice-free by 2100). This would greatly affect climate variability for Europe as well as affect river discharge levels, potentially increasing flood risks in winter and droughts in summer. Furthermore, in the long-term sediment yields and water quality will decline once the Alpine glaciers have retreated. In North Canada, the Yukon region has experienced rising temperatures. This has led to increased rain precipitation, as opposed to snow; estimated to increase by 5-20% by 2100. Furthermore, there is decreased snow cover (shrank by 20%) as it melts earlier, thereby increasing inflows to the Yukon River by 40%.

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*Threats to the Water and Carbon Cycle 2

Deforestation of Madagascar's Tropical forests since the 1950s has led to 2/3 of the forest being lost by 1985. A growing population and demand for hardwood led to more land being cleared and the government encouraging the growth of cash crops such as palm oil. Impacts include: Increased CO2 emissions; Loss of terrestrial carbon stores and biomass; Eutrophication; Reduced evapotranspiration and infiltration rates; Increased surface runoff and flood frequency/intensity; Soil erosion and leaching (loss of nutrients); Loss of habitats and biodiveristy; Displacement of indigenous tribes.

The conversion of 5.5 million hectares of grasslands into biofuel farms within Brazil, Malaysia and Indonesia increased soil erosion and water insecurity through eutrophication and increased irrigation. Furthermore, natural grasslands are a major terrestrial carbon store that is rapidly depleting.

Ocean Health: Globally, half of all mangrove forests have been lost since 1950. Mangroves are essential for the protection of coastlines against erosion as well as storm surges/floods. Warming waters are leading to a decline in Arctic Krill by 75%, affecting 520 million people that depend on fisheries for food and income.

The melting of arctic ice releases CO2 and Methane stored in the permafrost through a process called Arctic Amplification. However, the reduced permafrost cover has allowed vegetation to grow, allowing some scientists to speculate that a localised carbon carbon sink could form, causing more carbon to be sequestered than lost through respiration via a negative feedback loop. On the other hand, scientists argue that the volume of carbon released from permafrost could create also create a positive feedback loop that exacerbates global warming exceedingly high rates.

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*Risks of Climate Change

The burning of fossil fuels has depleted terrestrial stores whilst increasing atmospheric stores, creating an imbalance. Since the 1950s a noticeable change in global temperatures can be seen in Europe, with temperatures predicted to rise by over 6 degrees by 2100. This has caused the enhanced greenhouse effect, which increases the concentration of CO2 and methane that traps heat within the atmosphere; 75% of CO2 emission since the 1980s has come from fossil fuel emissions.

Human impacts on the carbon cycle also threaten to create positive feedback loops that threaten to surpass global "tipping points" or critical thresholds. These include:

  • Forest Die Back: Moisture within the Amazon Basin is recycled for rainfall, during droughts trees die back and stop the recycling of moisture 
  • Themohaline Circulation: The melting of nortern ice sheets could slow the convection current flow of water. This would limit carbon sequestration and potentially affect global temperatures
  • Ocean Acidification: The increased emission of CO2 has led to increased carbon sequestration in the oceans (~30% of emissions). This has decreased the pH of the ocean and, in combination with rising ocean temperatures, had consequences on the sensitive coral reef ecosystems. The ejection of vital algae causes coral to die and undergo "coral bleaching". A secondary impact of this is reduced tourism and income for local people.
  • Permafrost melt could release trapped carbon into the atmosphere, leading to further temperature increasing and melting
  • Peatlands dry out as water tables fall, increasing the normally low rate of decomposition within the soil. This would cause a 40% loss in carbon from the surface layer of soil and 86% from the deep peat layers.
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*The Future of Climate Change

The future of energy consumption and greenhouse gas emissions is expected to increase but it is uncertain as to what extent. Climate models estimate a 2-6 degrees average increase by 2100, with some regions such as the Arctic experiencing the greatest change. 

Kuznet's curve is a represenation that correlates Income per Capita to levels of Environmental Degradation. The curve is a maximum point, indicating environmental degradation peaks amongst the high-consuming middle-class. Low income citizens consume less and contrastly, high income citizens can afford to be more environmentally conscious.

Hubbert's Curve is an approximation of the production rate of a resource over time. It is  abell curve that supports the theory of "Peak Oil" (50% of supplies have been consumed). Whilst the initial discovery of oil leads to rapid consumption, as it becomes scarer, the rate of production slows but cannot meet increasing demands.

The future of climate change is uncertain for a range of reasons:

  • The Hydro and Bio sphere take decades to respond to changes in levels of greenhouse gas.
  • The rate of economic growth is not linear to rate of carbon emissions, as evidenced by the 2008 financial crisis in which their were peak carbon emissions
  • The implementation of renewable energy sources accounted for 2/3 of electricity produced in 2015
  • Population change and the growth of the middle class could affect energy consumption and "peak carbon"
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*Managing Climate Change - Adaptation

Adaptation Strategies involve living with impacts of climate change. They include:

  • Water Conservation - Israel has improved it's water efficiency through smart irrigation, recycling sewage water and increasing the price of water to fund conservation projects. In the long term this will reduce groundwater abstraction but ultimately could fail to meet increasing demands.
  •  Resilient Agriculture - Syria has grown GM crops that are drought-tolerant. Furthermore, conservation cropping is a sustainable technique that involves less fertilisers and retaining stubble to increase yields and improve soil quality, thereby increasing water conservation and carbon sequestration. However, the ethicicy of GM crops is debated and many resilient agriculture practises are expensive (e.g GM crops imported), therefore making them not very widespread.
  • Land use zoning - By limiting development on vulnerable floodplains, this reduces the amount of impermeable surfaces. In addition, creating green park areas will increase interception and infiltration rates, reducing surface run off and the spatial concentration of floods. Howvever, land use zoning is not popular and is often met with apathy from the public. It puts pressure on "safe zones" and relocating high-risk areas would be costly (financially and socially), e.g coastal megacities such as Dhaka, Bangladesh and Tokyo-Yokohama, Japan.
  • Flood Risk Management - Involves using hard engineering defences such as sea walls, rock armour and dredging to reduce coastal flood risk. Furthermore, the use of permeable tarmac can increase infiltration and reduce surface run off. However, this can cause conflict between stakeholders as coastal defences can be expensive to implement and maintain, thereby meaning it cannot be implemented holistically.
  • Solar Radiation Management - A form of climate engineering that would reflect solar rays to counteract global warming. It remains relatively untested, meaning it could have unknown consequences to the atmospheric system in the long term. Furthermore, only the effects of global warming would be rreduced, not other changes such as acidification. 
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*Managing Climate Change - Mitigation

Mitigation strategies involve fundamentally re-balancing the carbon cycle. They include:

  • Carbon Taxation - A fee on the use of fossil fuels in an aim to raise awareness for changing energy habits. The UK implemented a Carbon Price Floor (CPR), a minimum price for companies to emit CO2, in 2013, however it was frozen in 2015 due to backlash from industry and environmental groups.
  • Renewable Switching - The switching of fossil fuels to renewable sources. Sweden is the global leader will oil usage dropping by 55% between 1970 - 2020. Additionally, it has a large nuclear and HEP infrastructure which account for 80% of it's energy mix. This has led to comparatively low CO2 emissions despite high energy consumption; although there are concerns over the intermittent reliabilty of renewable sources (e.g time of day/weather)
  • Energy Efficiency - Aims to improve energy efficiency in buildings and manufacturing e.g with LED lights and improved insulation. Germany is a world leader in energy efficiency and has reduced energy consumption by 25% by renovating old properties and subsiding the cost of implementing these changes. In contrast, the UK attempted this with the Green Deal scheme but eventually scrapped it in 2015. 
  • Afforestation - Afforestation/Reforestation increase the terrestrial carbon store by planting trees. The Big Tree Plant campaign in the UK planted 1 million new trees, mainly within urban areas. In contrast, South Korea has a history of high deforestation, particularly during WW2 and the Korean War. However, reforestation attempts between 1960 - 1995 have restored the degraded environments, and in 2008 a total of 11 billion trees had been planted.
  • Carbon Capture & Storage (CCS) - Capturing CO2 emissions produced during the burning of fossil fuels and storing them in underground geogological formation such as aquifers. The Canadian Boundary Dam is the only large-scale, commercial CCS power plant and aims to reduce emissions by 1 million tonnes annually.

Climate agreements such as the 2015 Paris Agreement now focus on mitigation strategies, as they act globally and in the long-term, however they also support developing countries with adaptation methods for short-term relief. Their aim is to limit global temperatures to 1.5 degrees of pre-industrial levels as well as strengthen global resilience to climate change, particularly within LEDC.

Perceptions to climate change vary and governemtns disagree as to the best course of action. Some fear by reducing emissions, the conomic growth of developing countries could be hindered due to increased TNC manufacturing cost (e.g China's phase down not out at COP26). In contrast, local people affected by climate change, such as environmental refugees, are the most affected and require desperate support.

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Global Disaster Trends

The global trend for disasters is a general increase. While the number of geophysical/natural  hazards has remained relatively the same, the number of people affected has significantly increased compared to 50 years ago. Models such as the PAR model explain this through Root Causes, Dynamic Pressures and Unsafe Conditions. 

Some potential reasons for the trend of disasters are:

 - Rapid Urbanisation: The increased population density and financial infrastructure at risk

- Rise in Population: The rapid growth of population due to improving healthcare has led to improved maternal mortality rates. Furthermore, the size of vulnerable demographics such as the Elderly is increasing.

Despite this, recent trends have shown that deaths in HICs due to natural disasters are decreasing. This is potentially due to improvements in warning systems, defence technology and community preparation through education. However, the extent to which technology can mitigate disasters is limited, as deaths in LICs remain high due to a lack of resources and infrastructure.

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