The greenhouse effect is a naturally occurring process.

State one greenhouse gas.

The greenhouse effect is a naturally occurring process.

Explain how radiation of different wavelengths is involved in the greenhouse effect

The enhanced greenhouse effect can cause a rise in atmospheric temperature.

Outline two consequences of a global temperature rise on arctic ecosystems.

1. 

2.
 

The enhanced greenhouse effect can cause a rise in atmospheric temperature.

Outline one effect of a temperature rise on plants.

carbon dioxide / methane / oxides of nitrogen / water vapour / ozone / CFCs

incoming shorter-wave radiation/UV/visible passes through Earth’s atmosphere;
converted to longer-wave radiation/heat/infrared;
atmosphere absorbs/traps longer-wave radiation/infrared/heat;
Answers can be given in the form of an annotated diagram.
Answers must specify long wave/infrared/heat and short wave radiation.

increased rates of decomposition (of detritus in permafrost);
expansion of the range of habitats available to temperate species;
loss of ice habitat;
changes in distribution of prey species affecting higher trophic levels;
increased success of pest species/pathogens;
rise in sea levels;
Mark only the first two answers given.

rate of photosynthesis increases as temperature increases;
rate of transpiration increases as temperature increases;
shift in plant distribution / OWTTE;

Nearly all candidates could name a greenhouse gas.

The explanations of the greenhouse effect in (a) (ii) were on average better than when this question had been asked before. Some candidates were still confused between the greenhouse effect and the effects of the ozone layer but many successfully described the difference between short and long wave radiation in penetration of the atmosphere. The absorption of short wave radiation by the Earth’s surface and emission of longer wavelengths by the heated surface were less well described

Part (b) (i) was an easy question and many candidates scored both marks. Candidates should be encouraged to write more than a short phrase as an answer to an “outline” question as in some cases too little had been stated for one of the points on the mark scheme to have been earned.

Part (b) (ii) is another question where it was safer to write one or two sentences than just a word or short phrase. Many candidates outlined the effect of global temperature rises on photosynthesis. Only those who stated that photosynthesis rates would rise were given a mark. Those that predicted a fall, based this on a prediction that enzymes used in photosynthesis would be denatured. The temperature rise due to the enhanced greenhouse effect is unlikely to be large enough to cause this. Smaller temperature rises might cause an increase in photorespiration but this was not the reason for a fall that candidates were giving.