Carbon Cycle
Carbon is one of the most important and abundant elements on earth, existing in rocks, atmosphere, ocean, soil, fossil fuels and plants. Carbon is an essential elements because it is needed by every organism either for energy or structure. The carbon cycle is the process that describes the flow or movement of carbon from one reservoir to another. These reservoirs include vegetation, soil, oceans, rocks and atmosphere. The cycle consists of several reservoirs and processes which take place when the carbon flows between the reservoirs (Riebeek, 2011).It is important to note that the shift of carbon from one reservoir results in more carbon concentration in other reservoirs. A ‘net carbon sink’ is a pool whereby more carbon flows into it than leaves it. A ‘net carbon source’ is a pool whereby more carbon leaves it than it enters into it. In a nutshell, the carbon cycle has geological and biological components which are distinguished by the time scale in which they take place (Riebeek, 2011).
Geological carbon cycle
The geological carbon cycle (slow carbon cycle) is whereby carbon takes 100-200 million years to flow between the rocks, soil, surface water bodies (ocean and rivers) and atmosphere (Riebeek, 2011).The processes involved include weathering and dissolution, volcanic eruptions, precipitation of mineral as well as burial and subduction. While in the atmosphere, atmospheric CO 2 mixes with water to form carbonic acid which later falls as acid rain. The acid rain dissolves the minerals and rocks on the earth surface through the process of chemical weathering (Riebeek, 2011). The resultant ions after the chemical process are carried away by rain water into rivers and oceans and eventually precipitate as minerals such as calcite. Over time, the calcite sediments forms limestone. The cycle continues as the seafloor is pushed under continental margins through subduction. As the tectonic forces push the seafloor deeper into the earth, the seafloor heats up and melts and eventually rises back to the earth surface, releasing carbon dioxide into the atmosphere. The return of CO 2 into the atmosphere occurs through volcanic eruptions or in seeps, vents and carbon dioxide-rich hot springs (Riebeek, 2011).
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Biological carbon cycle
This is the fast carbon cycle that describes the flow of carbon between soil, ocean and the atmosphere through photosynthesis and respiration (Riebeek, 2011). Plants and microscopic organisms found in the ocean take up CO 2 from the atmosphere and use solar energy to from oxygen and carbohydrates (sugars) through the process of photosynthesis. The plants then use the carbohydrates by breaking them down to get the energy necessary for growth (Riebeek, 2011).This process is known as respiration. This processes releases energy used in metabolism and converts the carbohydrate fuel back to CO 2, which is later released into the atmosphere. The amount of atmospheric carbon dioxide taken up for photosynthesis and released through respiration is approximately 1000 times more than the carbon that flows in the geological carbon cycle on a yearly basis (Riebeek, 2011).
Past and Current CO 2 concentration
The United States Department of Energy has, for many years, supported the Scripps CO 2 program at Mauna Loa Observatory in Hawaii. Since the year 1958, Mauna Loa has been gathering data concerning the concentration of atmospheric carbon dioxide. Recently, the program has been supported by the Earth Networks to expand the GHG monitoring network worldwide. Recent data from the Scripps indicate the concentration of atmospheric CO 2 is approximately 408.66 in parts per million (ppm). According to the graph, the current CO 2 concentration is much higher than concentration recorded in 400, 000 years which was about 300 ppm. Research shows that industrial revolution and other human-related activities have contributed to the rise of atmospheric CO 2.
Sources of human-induced CO 2 and Carbon Sinks
Research shows that, although there is a certain amount of CO 2 that exits naturally in the atmosphere, human activities have contributed to the increase of atmospheric carbon dioxide levels. The increased levels of CO 2 in the atmosphere remains an issue of concern, taking into account the adverse effects or consequences associated with it. There is growing evidence showing that transportation, industrial revolution and burning fossil fuels are the most common sources of human-induced carbon dioxide worldwide (Environmental Protection Agency, 2018).
Fossil fuels are hydrocarbons that are used as a source of energy in transportation and electricity sectors of many developed and developing countries. They include coal, natural gas and fuel oil. Concern about the burning of fossil fuels can be linked to the negative consequences it has on the environment as well as public health. Research shows that burning fossil fuels produces harmful air pollutant, including carbon dioxide, Sulphur dioxide, methane and other toxic substances. Fossil fuels account for about 28.4% of greenhouse gas emissions in the United States (EPA, 2018). Methane and carbon dioxide contribute to climate change while Sulphur dioxide contribute to acid rain.
Industrial revolution which involves the manufacturing of cement, iron and steel is another source of CO 2 emission, especially in the developing countries. Greenhouse gases emitted by manufacturing and textile industries include methane, nitrous oxide and carbon dioxide. Industries amount to 22% of greenhouse gas emissions in the US (EPA, 2018). The transportation sector is another human-related activity that has been proven to have contribute the rising CO 2 levels in the atmosphere. In the US, it the transportation sector is the considered as the largest source amounting to about 28.5 % greenhouse gas emissions (EPA, 2018). Fumes emitted by vehicles and trains contains a high concentration of carbon which accumulates in the atmosphere, resulting in global warming.
The two main carbon sinks that remove excess carbon dioxide which has accumulated in the atmosphere are oceans and trees. Ocean water is able to absorb atmospheric CO 2 due to the action of the waves and turbulence triggered by the wind. Trees and plants act as carbon sinks as they absorb CO 2 which is necessary for photosynthesis.
Deforestation and greenhouse gases
One way in which cutting down of trees (deforestation) contributes to the increase of atmospheric carbon dioxide is by reducing the tree carbon sink available for ‘cleaning’ the air. Another way that deforestation contributes to an increase of CO 2 levels is by limiting the process of carbon sequestration. This is the process whereby trees remove excess carbon dioxide by absorbing it and using it for photosynthesis. Therefore, cutting down trees reduces or limits or reduces carbon sequestration. Other than CO 2, other greenhouse gases include methane, nitrous oxide, water vapor, chlorofluorocarbons and hydrofluorocarbons.
Conclusion
Based on the data and information provided in this paper, it is clear that human beings are the main contributors to global warming and climate change not only in the United States but also elsewhere around the world. This is because the concentration of CO 2 and other greenhouse gases in the atmosphere has been linked to human activities such as transportation, burning of fossil fuels and industries.
References
Riebeek, H. (2011, June 16). The Carbon Cycle . Retrieved from https://earthobservatory.nasa.gov/features/CarbonCycle
United States Environmental Protection Agency. (2018, October 9). Sources of Greenhouse Gas Emissions . Retrieved from https://www.epa.gov/ghgemissions/sources-greenhouse-gas- emissions
