Describe the pattern of high physical water scarcity shown on the map.

Explain why some of the world’s arid areas are not areas of physical water scarcity.

Explain the energy flows involved in the greenhouse effect.

Any of the following for [1 mark] each:

• a valid comment on latitudinal location 
• mainly found in the northern hemisphere 
• especially in Northern and Eastern Africa and parts of Southern Africa 
• Middle East 
• SW and/or Central Asia 
• SW North America 
• West coast of South America.

Physical water scarcity occurs when water resource consumption is approaching or has reached unsustainable levels/demand exceeds 60% of usable supply. Award [1 mark] for describing this concept. The world’s arid areas have little available water, but usually have low population/density [1 mark] and therefore water usage/demand may still not exceed sustainable levels/supply [1 mark].

Any of the following:

• incoming solar radiation/shortwave radiation/insolation 
• some reaches the Earth’s surface 
• the Earth’s surface re-emits terrestrial/longwave radiation 
• some of this energy/radiation is absorbed/trapped by greenhouse gases 
• a little energy is lost to space 
• naming two or more valid greenhouse gases.

There is no requirement to explain the enhanced greenhouse effect.

A valid annotated diagram explaining five of the above is equally acceptable.

This was a very straightforward question with most candidates achieving full marks. However, description needed to be specific and geographical in nature – left and right or entire continents in the description were not credited. Many candidates incorrectly stated that most high physical water scarcity is on the equator, which is not the case. Some responses seemed to veer off into explanation, which was not required by the command term (“describe”).

This was probably the question that most candidates struggled with. The nature of this question allowed for only a very narrow response and if the candidates were unfamiliar with what physical water scarcity is they failed to answer this question appropriately. There were however some very clear answers that defined the term and identified the link between population numbers and demand, with many giving illustrations from a variety of global locations.

Many good answers used an annotated diagram to illustrate the flows of energy although the majority answered through extended text. Many candidates are very familiar with the greenhouse effect and could adequately explain the energy flows and gases involved, often achieving full marks. There were still a surprising number who got muddled up with ozone depletion or who could only describe the enhanced greenhouse effect.