Two of the major greenhouse gases in the atmosphere are methane and carbon dioxide. State two other major greenhouse gases.

Discuss which two gases from the four gases in part (a) are the most significant for global warming.

Discuss two effects of global warming.

\({{\text{H}}_{\text{2}}}{\text{O}}\);

\({{\text{N}}_{\text{2}}}{\text{O}}\)/nitrous oxide/dinitrogen monoxide/nitrogen(I) oxide;

chlorofluorocarbons/CFCs/e.g. \({\text{CC}}{{\text{l}}_{\text{2}}}{{\text{F}}_{\text{2}}}\);

\({{\text{O}}_{\text{3}}}\)/ozone;

\({\text{S}}{{\text{F}}_{\text{6}}}\);

Do not accept NOx/nitrogen oxides.

Accept names or formulas.

Gas: \({{\text{H}}_{\text{2}}}{\text{O}}\) and reason: greatest abundance;

Gas: \({\text{C}}{{\text{O}}_{\text{2}}}/{{\text{H}}_{\text{2}}}{\text{O}}\) and reason: greatest abundance;

Gas: \({\text{C}}{{\text{H}}_{\text{4}}}/{{\text{N}}_{\text{2}}}{\text{O}}\) and reason: more effective at absorbing radiation;

Gas: \({\text{CFC}}/{\text{S}}{{\text{F}}_{\text{6}}}\) more effective at absorbing radiation/very long life in atmosphere;

thermal expansion of the oceans / changes in sea temperature affecting sea life;

melting of the polar ice-caps/glaciers / rising sea levels;

floods / droughts / changes in precipitation and temperature;

changes in migration patterns of animals / changes in distribution of species / species more likely to become naturalized;

changes in the yield/distribution of crops;

changes in the distribution of pests/insects/pathogens/disease-carrying organisms;

Do not accept “climate change”.

Some candidates were not able to provide two more major greenhouse gases. Many candidates stated \({\text{N}}{{\text{O}}_{\text{2}}}\) rather than \({{\text{N}}_{\text{2}}}{\text{O}}\) as a greenhouse gas.

Candidates also had some difficulty explaining which greenhouse gases were most significant. Candidates only gave the name of the most significant greenhouse gas but did not provide an explanation.

Although most candidates were able to discuss two effects of global warming, some candidates confused global warming with the depletion of the ozone layer. Candidates were also expected to discuss the effects of global warming rather than just restate the question by stating that the atmospheric temperature would increase.