5.1: Background
- Page ID
- 28681
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)A major player in changing climate is carbon in its various forms. This is in large part because of how increasing levels of carbon dioxide in the atmosphere are impacting the energy budget of the earth’s climate. Key to understanding this impact is understanding how carbon moves through the climate system via a process known as the carbon cycle.
The carbon cycle is the continuous exchange of carbon between living organisms, the oceans, atmosphere, and the earth’s crust. During this exchange various carbon compounds are continuously created, destroyed, and stored. Chief among these compounds are carbon dioxide (\(CO_{2}\)), methane (\(CH_{4}\)), calcium carbonate (\(CaCO_{3}\)), and hydrocarbons (\(H_{x}C_{y}\)). The chief mechanisms by which this happens include…
- Respiration of animals, plants, and microbial life
- Production of methane via digestion and decomposition
- Photosynthesis by plants and microbial life
- Atmosphere-ocean exchanges
- Combustion of fossil fuels and vegetation
- Volcanic eruption
- Weathering of rock at the earth’s surface
Figure 5.1.1 is a diagram of this cycle that you will use for activity A. The diagram shows principle carbon flows and storages. One of your tasks in this activity will be to identify these exchanges and major carbon reservoirs. Your task in Activity B will be to investigate how we influence this cycle and the consequences of that influence.
Figure 5.1.1 is a diagram of the global carbon cycle showing principal flows and storage of carbon in its various forms. The diagram is divided into three “spheres”, the atmosphere, ocean, and geosphere (earth’s crust). The yellow arrows show the flow of carbon compounds between these three spheres, initials identify the principle mechanisms by which these exchanges take place, and chemical formulas identify principle forms of carbon. Additional information is available in the legend below.
Table 5.1.1Legend for Diagram 1 |
L1 – Principal forms of carbon shown in the diagram
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L2 – Principal natural carbon flows
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L3 – Principal human related carbon flows
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L4 – Principal carbon reservoirsCapacity of these reservoirs in GT or gigatons where 1 GT = 10 billion tonnes values from UNEP/GRID-Arendal Carbon Cycle Diagram <https://www.grida.no/resources/5050> Oceans
Atmosphere – 750 GT Geosphere (the earth’s crust)
Biosphere (the total living community of the planet) – 540 to 610 GT |
L5 – Principal carbon flowsThese flows are in GT/yr or gigatonnes per year. These values are derived from UNEP/GRID-Arendal Carbon Cycle Diagram <https://www.grida.no/resources/5050>
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Table \(\PageIndex{1}\)
Residence time – In the case of the carbon cycle, this is the average length of time that carbon compounds remain in the various reservoirs listed in L4. Understanding how major greenhouse gasses influence the climatic energy balance of our planet is largely a matter of looking at the warming potential of these gasses and their abundance in the atmosphere. In turn, atmospheric abundance of these gasses is dependent on their atmospheric residence time.
The table below (Table 5.1.2) lists five key greenhouse gasses. In addition to showing their approximate abundance in the atmosphere and their contribution to the greenhouse effect, it also shows their Global Warming Potential (GWP) and their atmospheric residence time. The latter is a measure of the warming potential of each gas relative to an equal mass of \(CO_{2}\). For instance, a kilogram of \(CH_{4}\) has 28 times the warming potential of a kilogram of \(CO_{2}\). However, \(CO_{2}\) contributes more to the greenhouse effect because of its higher abundance. Something that is strongly influenced by its longer residence time.
Table 5.1.2Key characteristics of principal Greenhouse Gasses. From Kiehl and Trenberth (1997) and Blasing T.J (2016) <https://cdiac.ess-dive.lbl.gov/pns/current_ghg.html> |
| Gas | Abundance in the atmosphere (%) | Atmospheric residence time | GWP | Greenhouse Effect Contribution (%) |
| Water vapor (\(H_{2}O\)) | 1 to 3 | Hours – days | n/a | 36 – 72 |
| Carbon dioxide (\(CO_{2}\)) | ~ 0.038 | 100 – 300 years | 1 | 9 – 26 |
| Methane (\(NH_{4}\)) | ~ 0.00018 | 12 years | 28 | 4 – 9 |
| Nitrous oxide (\(N_{2}O\)) | ~ 0.0006 | 121 years | 265 | n/a |
| Ozone (\(O_{3}\)) | ~ 0.0006 | Hours – days | n/a | 3 -7 |
Table \(\PageIndex{2}\)