Identify two greenhouse gases not mentioned above. One of the gases that you identify should contain a nitrogen atom. For each gas, state its source.

Greenhouse gas 1:

Source:

Greenhouse gas 2:

Source:

The methane produced by sheep and cows can contribute to global warming. In Australia, it is considered that sheep and cows produce approximately 14% of the country’s total greenhouse emissions. Explain how this methane is formed.

The following graph shows the annual increase in the concentration of atmospheric carbon dioxide recorded at Mauna Loa, Hawaii.

Explain why the graph is not smooth but involves annual fluctuations (shown in grey).

State one effect of global warming.

\({{\text{N}}_2}{\text{O}}\);

artificial fertilizers / combustion/decomposition of biomass;

Award [2 max] for one of the following pairs.

\({{\text{H}}_2}{\text{O}}\);

evaporation of oceans/lakes;

OR

\({\text{S}}{{\text{F}}_6}\);

insulator in electrical industry;

OR

\({{\text{O}}_3}\);

photochemical smog / electrical generators;

Allow correct names (e.g. ozone) instead of formulas.

Sources must match gases for [1].

breakdown of grass in animals stomachs / microbes in animals stomachs / by-product of fermentative digestion in rumen (and hind gut);

seasonal since plants grow in spring and decay in autumn/fall / amount of \({\text{C}}{{\text{O}}_{\text{2}}}\) in the atmosphere depends on (natural processes such as) photosynthesis, which happens (more) in spring and summer than in autumn/fall and winter;

rise in sea levels / thermal expansions of the oceans;

melting polar ice-caps/glaciers;

changes in climatic patterns / OWTTE;

changes in agriculture and bio-distribution / OWTTE;

Allow specific changes.

Part (a) required candidates to identify two greenhouse gases not mentioned already in the stem of the question. It was also stated that one of these gases should contain a nitrogen atom. Only the best candidates could identify two greenhouse gases and their sources. There were many incorrect responses, and many responses that did not meet the requirements of the question.

Parts (b) and (c) indicated that candidates did not have sufficient experiences of real situations to set their knowledge in context, and few candidates linked the annual fluctuations to seasonal changes in photosynthesis. Some G2 comments reflected that teachers felt these questions were not directly related to the syllabus, but E.3.2 indicates that candidates should have familiarity with these sources.

Parts (b) and (c) indicated that candidates did not have sufficient experiences of real situations to set their knowledge in context, and few candidates linked the annual fluctuations to seasonal changes in photosynthesis. Some G2 comments reflected that teachers felt these questions were not directly related to the syllabus, but E.3.2 indicates that candidates should have familiarity with these sources.

Nearly all candidates could state one effect of global warming in (d).