Climate change and the global wine industry

Climate change has the potential to greatly impact nearly every form of agriculture. However, history has shown that the narrow climatic zones for growing winegrapes are especially prone to variations in climate and long-term climate change. While the observed warming over the last fifty years appears to have mostly benefited the quality of wine grown worldwide, projections of future warming at the global, continent, and wine region scale will likely have both beneficial and detrimental impacts through opening new areas to viticulture and increasing viability, or severely challenging the ability to adequately grow grapes and produce quality wine. Overall, the projected rate and magnitude of future climate change will likely bring about numerous potential impacts for the wine industry, including – added pressure on increasingly scarce water supplies, additional changes in grapevine phenological timing, further disruption or alterations of balanced composition and flavour in grapes and wine, regionally-specific changes in varieties grown, necessary shifts in regional wine styles, and spatial changes in viable grape growing regions. Climate change, viticulture, and wine The grapevine is one of the oldest cultivated plants that, along with the process of making wine, have resulted in a rich geographical and cultural history of development ( Johnson 1985, PenningRoswell 1989, Unwin 1991). Today’s viticultural regions for quality wine production are located in relatively narrow geographical and therefore climatic niches that put them at greater risk from both short-term climate variability and long-term climate change than other more broad acre crops. In general, the overall wine style that a region produces is a result of the baseline climate, while climate variability determines vintage quality differences. Climatic changes, which influence both variability and average conditions, therefore have the potential to bring about changes in wine styles. Our understanding of climate change and the potential impacts on viticulture and wine production has become increasingly important as changing levels of greenhouse gases and alterations in Earth surface characteristics bring about changes in the Earth’s radiation budget, atmospheric circulation, and hydrologic cycle (IPCC 2001). Observed warming trends over the last hundred years have been found to be asymmetric with respect to seasonal and diurnal cycles with greatest warming occurring during the winter and spring and at night (Karl et al. 1993, Easterling et al. 2000). The observed trends in temperatures have been related to agricultural production viability by impacting winter hardening potential, frost occurrence, and growing season lengths (Carter et al. 1991, Menzel and Fabian 1999, Easterling et al. 2000, Nemani et al. 2001, Moonen et al. 2002, Jones 2005a). To place viticulture and wine production in the context of climate suitability and the potential impacts from climate change, various temperature-based metrics (e.g. degree-days, mean temperature of the warmest month, average growing season temperatures, etc.) can be used for establishing optimum regions (Gladstones 1992). For example, average growing season temperatures typically define the climate-maturity ripening potential for premium quality wine varieties grown in cool, intermediate, warm, and hot climates ( Jones 2006; Figure 1). For example, Cabernet Sauvignon is grown in regions that span from intermediate to hot climates with growing seasons that range from roughly 16.5–19.5°C (e.g. Bordeaux or Napa). For cooler climate varieties such as Pinot Noir, they are typically grown in regions that span from cool to lower intermediate climates with growing seasons that range from roughly 14.0–16.0°C (e.g. Northern Oregon or Burgundy). From the general bounds that cool to hot climate suitability places on high quality wine production, it is clear that the impacts of climate change are not likely to be uniform across all varieties and regions, but are more likely to be related to climatic thresholds whereby any continued warming would push a region outside the ability to produce quality wine with existing varieties. For example, if a region has an average growing season temperature of 15°C and the climate warms by 1°C, then that region is climatically more conducive to ripening some varieties, Figure 1. The climate-maturity groupings given in this figure are based on relationships between phenological requirements and climate for high to premium quality wine production in the world’s benchmark regions for each variety. The dashed line at the end of the bars indicates that some adjustments may occur as more data become available, but changes of more than +/0.2–0.6°C are highly unlikely. The figure and the research behind it are a work in progress (Jones 2006) Cool Intermediate Warm Hot