Explain how the interaction of greenhouse gases in the atmosphere with radiation could lead to an increase in the temperature of the Earth’s surface.

Suggest why carbon dioxide is the greenhouse gas most frequently connected with the effect of human activity.

Other than carbon dioxide and water, identify one other greenhouse gas and state its source.

shorter wavelength/UV/high energy radiation from sun passes through;

long wavelength/infrared/IR radiation from Earth’s surface (some of this radiation) is absorbed (by gas);

Do not accept “trapped” or “blocked”.

Do not accept “IR from sun”.

causes (increased) vibration in bonds;

re-radiates heat back to the Earth;

Do not accept “reflects/bounces”.

higher concentration / more abundant/increased combustion of fossil fuels (than other anthropogenic sources);

methane/\({\text{C}}{{\text{H}}_{\text{4}}}\);

decomposition of organic matter / animals / oil fields / gas fields / intensive farming / landfills;

OR

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

Do not accept NO_x, NO, NO₂, nitrogen oxides.

decomposition of organic matter/fertilizers;

OR

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

photochemical smog;

OR

CFCs;

aerosol cans / air conditioners / solvents / foam production / refrigerants;

OR

sulfur hexafluoride/\({\text{S}}{{\text{F}}_{\text{6}}}\);

electrical insulator;

OR

nitrogen trifluoride/\({\text{N}}{{\text{F}}_{\text{3}}}\);

production of electronic components;

[1] for any correct gas and [1] for the corresponding source.

There seems to be a very poor understanding of the interaction of greenhouse gases with radiation although this question has frequently appeared in the examinations. A surprising number quoted ozone depletion and the use of terms often used in the media e.g. “trapped”, “bounces”.

In part (b), the candidates failed to state the increased combustion of fossil fuels.

Although the question stated “other than carbon dioxide and water identify one other green house gas”, many candidates identified \({\text{C}}{{\text{O}}_{\text{2}}}\) and \({{\text{H}}_{\text{2}}}{\text{O}}\).