WINETECH Technical Yearbook 2020

regions considering temperature and rain- fall only. The topography and distance from the ocean seemed to drive regional shifts over the three decades (1984-2015), with a more pronounced effect on temperature in the coastal region, some regions being more prone to change, emphasising the need for finer scale demarcation when cli - mate aspects are considered. The analysis highlights the need for regional and month- ly review in the context of climate change to be focused on maximum and minimum temperature, as when averages are used, the meaning of the data is masked. Figure 2 explains what has happened in the dif- ferent wine-producing regions over the last 10 years compared to the long-term mean. For example the Breede River Valley is seeing increases in maximum temperatures and decreases in minimum temperatures, this could mean that the region could expect more heatwaves or higher summer temperatures along with cooler winters/ spring temperatures that could manifest in the form of frost. The incidence of frost has increased in some areas within the Breede River Valley the past few seasons, having a significant impact on the crop load at harvest. The increases in rainfall in the Breede River Valley could have positive or negative impacts, very much dependent on the timing of rainfall. Figure 2 can be used to aid decision making in the context of a changing climate, some

regions more prone to increased/decreased temperatures and other more prone to changes in rainfall, this knowledge could aid viticulture management strategies. Climatic indices used to summate the seasonal growing temperatures have showed significant increases. This trend is continuing and is shifting the climate zone demarcations for viticulture. However, in the context of climate change, seasonal summations are not enough to quantify the impact of temperature shifts on the grapevine. A higher temporal resolution of weather conditions is required, and highlights that the seasonal summations are driven by warmer than normal months later in the season, specifically driven by increases in temperatures in the months of December, January and March (figure 3). The growing season is warming and demarcated areas linked to specific production and cultivar targets need to be reviewed. Monthly temperature shifts, rather than regional temperatures, better illustrated the fluctuations of temperatures across the decades. The most significant shift to warmer temperatures was noted in December, January and March, with increasing rainfall in January and March, insights that could affect the grapevine’s growth and especially ripening. Cooler minimum temperatures in September could affect budburst and the cooling temperatures in November, along with

The data clearly highlighted: a general warming trend within the extent of the Western Cape over the last 30 years, regions and months responding differently. The results showed significant differences in the warming and cooling over decades (10 years), half decades (five years), years, regions and months. There was a significant climatic trend of warming for the 30-year period, with a similar trend across the different wine regions of South Africa. Over all temperature elements, there was a warming trend from 1984-2015, maximum temperatures showed the most increase of between 1-2°C and minimum temperature increases were observed over all

the regions, but with less intensity (<0.6°C). Temperatures in the Western Cape are projected to increase by as much as 1.5°C along the coast and 3°C inland by 2050. Rainfall was not well explained by specific long-term trends, but regional and monthly changes of annual increases and decreases over decades, with a general trend of rainfall shifting more into the summer season of the Western Cape. The 30-year long-term temperature and rainfall averages for each wine producing region are described in Table 1, highlight- ing the cooler and warmer production ar- eas. Figure 2 highlights the climate change impacts on the different wine-producing

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