4.2 Carbon Cycling & Climate Change

The following data show fluxes in carbon between different storage reserves in an ecosystem, measured in gigatonnes per year (GT yr^-1). A gigatonne equals 1 billion tonnes.

Calculate the net flux of carbon. Show your working.

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State the direction of this movement with regards to the atmosphere.

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Explain how the combustion of fossil fuels can affect the carbon balance in the atmosphere.

Estimating global carbon fluxes are of great interest to scientists, even though it may be challenging to make accurate measurements.

Discuss the scientific importance of estimating carbon fluxes.

Methane is an example of a greenhouse gas that commonly occurs in the atmosphere. The graph below shows the main sources of methane as well as the percentage contribution of the different components of each source. A teragram (Tg) equals 10¹² grams and is equivalent to one megatonne (1 million tonnes).

Calculate the amount of methane, in Tg year^-1, that is released from wetlands. Show your working.

Suggest a reason why wetlands would be the largest contributor of atmospheric methane, as shown in the graph above.

Recent studies predict a decrease in levels of hydroxyl radicals in the atmosphere of between 10% and 16%. Hydroxyl radicals are often called the 'detergent of the atmosphere' and plays an important part in regulating atmospheric levels of gases such as methane.

Predict the possible long-term effect these decreased levels of hydroxyl radicals could have on atmospheric concentrations of methane.

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Explain your answer to part c) i).

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Carbon dioxide is one of the main greenhouse gases in the atmosphere. The graph below shows the changes of carbon dioxide levels in the atmosphere, as well as the change in global temperatures over a period of time.

Describe the general trends in the data.

Suggest possible causes of the trends in the data presented in part (a).

Discuss the importance of greenhouse gases, such as carbon dioxide, in the atmosphere.

One mark is available for clarity of communication throughout this question.

Coal, oil and natural gas are all examples of fossil fuels that can be utilised as an energy source.

Compare and contrast the formation of coal with that of oil and natural gas.

The amount of carbon in the atmosphere is constantly changing over time. Carbon dioxide and methane gases contribute to carbon levels in the atmosphere and have important impacts on the planet.

Discuss the importance of obtaining reliable data on the atmospheric concentration of these gases over time.

Suggest the possible impact that an increase in global temperatures would have on the polar regions, as well as the global consequences of this impact.

The graph below shows changes in atmospheric carbon dioxide levels between 1960-2010, recorded at Mauna Loa observatory, Hawaii.

Estimate the increase in average atmospheric carbon dioxide concentration between 1960 and 2000.

Suggest why yearly fluctuations occur in actual atmospheric carbon dioxide concentration, as seen in the graph in part (a) above.

In addition to collecting data on atmospheric carbon dioxide levels, scientists also collect data on average global temperatures. Both sets of data between the years 1000 and 2000 are shown together in the graph below.

Evaluate the claim that rising global temperatures are caused by rising atmospheric carbon dioxide levels.

State what the graph shows about the impact of human activities on atmospheric carbon dioxide levels andaverage global temperatures.  Note that the industrial revolution began in the mid 1700s.

The diagram below illustrates the greenhouse effect.

Explain why a higher proportion of the sun’s radiation reaches the earth’s surface than escapes back into space.

The table below shows the global warming potential (GWP) of some other greenhouse gases in relation to carbon dioxide.

Methane has more than 80 times the radiation absorbing ability of carbon dioxide. Given that this is the case, explain the GWP value for methane shown in the table above.

Despite the GWP of water vapour shown in the table in part (a) it has a very powerful short-term warming effect.

Suggest why water vapour has such a strong short-term warming effect.

Other than the burning of fossil fuels, state three sources of atmospheric greenhouse gases.

A study was carried out on the impact of peat swamp forest drainage for the purpose of planting palm oil plantations on greenhouse gas emissions. Some of the results are shown below. Note that Rh denotes heterotrophic respiration.

Explain the difference in carbon dioxide emissions between peat swamp forest Rh and drained forest Rh.

A local councillor suggested that the data shows that planting oil palms would go some way to reducing the climate damage caused by draining the peat swamp.

Evaluate this suggestion.

The study described in part (a) was carried out by analysing the processes taking place in 25 m by 25 m quadrats.

Outline how the researchers could have ensured that their results from quadrat sampling were valid.

One mark is available for clarity of communication throughout this question.

Draw a labelled diagram of the carbon cycle.

Outline the impacts of increasing average global temperatures.

A common claim among people who are skeptical of climate science is that because rates of warming have not been consistent, global warming has in fact slowed down or stopped.

Discuss the factors that should be considered when deciding whether or not a claim such as this is valid.