Method
Hot Days
Fruit crops have critical upper temperature limits for growth and fruit quality. At air temperature > 35°C, many physiological processes (e.g. photosynthesis) decline, certain metabolites (e.g. red pigment) begin to be destroyed, and tissue damage (e.g. sunburn) can occur.
The number of days per annum when the maximum air temperature exceeds 35°C was calculated from daily temperature data. More detail is provided in the section Background: Climate Change Modelling.
The modelling for the intermediate future (2050s) was conducted using five different CMIP3 GCMs (Schulze, 2011).
Maps
Map Information
In the following maps, days > 35°C is presented under historical climatic conditions, under intermediate future climatic conditions (2050s), and as the projected change from the historical climatic conditions to the intermediate future climatic conditions (2050s).
Under the projections for the 2050s, much of the region will experience up to 20 additional days > 35°C. In the worst affected regions of the north-west, the northern and north-east border (Central Karoo), and parts of the Klein Karoo, 30 to 50 additional hot days could be experienced per annum.
The projected increases in very hot days will particularly impact fruit production in regions that today are already hot. Heat stress will result in high evaporative water losses from soil and water bodies and through transpiration, and irrigation demand will increase. The risk of sunburn increases under such conditions.