Describe how the estimated impact of climate change on agricultural production varies with latitude.

Suggest two reasons why global climate change may lead to an increase in agricultural production in some places.

Distinguish between physical water scarcity and economic water scarcity.

Award [1] for each valid point, must have some quantification for [3]. Three valid comments are required before quantification can be applied.

Possibilities include:

• very adverse impacts at latitudes between 10° and 35° (-30 to -40%) [1]
• least impact, or a positive impact, at latitudes of 40° plus (-5 to +10%) [1]
• mixed range at very low latitudes, near equator, 0° to 10° (-5 to approx. -20%) [1]
• anomalies at certain latitudes (one country with higher increase than expected at latitude 27° and two countries with unusually adverse impacts at 17°) [1]
• overall impact decreases away from the Equator [1]
• impact worsens 0º to 20º [1] 
• from 20º to 60º the impact gets less [1].

In each case, award [1] for a valid reason and [1] for further development/exemplification.

For example: Global climate change may lead to warmer temperatures, lengthening the growing season [1], which may enable farmers to produce two crops each year where it was previously only possible to produce a single crop [1].

Other possibilities include:

• more rain than previously, so higher yields
• warmer climate may extend growing season/cultivation into areas previously too marginal for farming
• milder winters may decrease cold stress on livestock
• more land available through glacial retreat or melting of permafrost – can be used for farming.

Award [2] for physical water scarcity and [2] for economic water scarcity.

In each case award [1] for a basic description and [1] for development/exemplification.

The definition in the subject guide is as follows:

• Physical water scarcity, where water resource development is approaching or has exceeded unsustainable levels; it relates water availability to water demand and implies that arid areas are not necessarily water scarce.
• Economic water scarcity, where water is available locally but not accessible for human, institutional or financial capital reasons.

For example:

• Physical water scarcity relates water availability/supply to water demand [1]. It means that water resource development is approaching (or has exceeded) a level that is unsustainable [1]. (Drought needs to be put into the context of supply/demand for development credit.)
• economic water scarcity means that water is available locally, but cannot be accessed [1] owing to issues of “human, institutional or financial capital” / cost / technology / incomes / etc [1].

Distinction can be implied and does not have to be explicit.