Climate Change and Wine

Climate is a pervasive factor in the success of all agricultural systems, influencing whether a crop is suitable to a given region, largely controlling crop production and quality, and ultimately driving economic sustainability. Climate’s influence on agribusiness is never more evident than with viticulture and wine production where climate is arguably the most critical aspect in ripening fruit to optimum characteristics to produce a given wine style.

History has shown that wine production occurs in relatively narrow geographical and climatic ranges. In addition, winegrapes have relatively large cultivar differences in climate suitability further limiting some winegrapes to even smaller areas that are appropriate for their cultivation. These narrow niches for optimum quality and production put the cultivation of winegrapes at greater risk from both short-term climate variability and long-term climate changes 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.Research has shown that high quality wine production globally is limited to areas with approximately 55-72°F average growing season temperatures (Figure 1). The climate-maturity groupings in Figure 1 were developed based upon both climate and plant growth for many cultivars grown in cool to hot regions throughout the world’s benchmark areas for those winegrapes. While many of these cultivars are grown and produce wines outside of the bounds depicted in Figure 1, these are more bulk wine (high yielding) for the lower end market and do not typically attain the typicity or quality for those same cultivars in their ideal climate. Furthermore, growing season average temperatures below 55°F are typically limited to hybrids or very early ripening cultivars that do not necessarily have large-scale commercial appeal. At the upper limits of climate, some production can also be found with growing season average temperatures greater than 70°F, although it is mostly limited to fortified wines, table grapes and raisons.

An example of cool climate suitability is found with Pinot Noir, Oregon’s marquee cultivar, which is typically grown in regions that span from cool to lower intermediate climates with growing seasons that range from roughly 57.0-61.5°F. The coolest of these is the Tamar Valley of Tasmania, while the warmest is the Russian River Valley of California. Across this 4.5°F climate niche, Pinot Noir produces the broad style for which is it known with the cooler zones producing lighter, elegant wines and the warmer zones producing more full-bodied, fruit-driven wines. While Pinot Noir can be grown outside the 57.0-61.5°F growing season average temperature bounds, it typically is unripe or overripe and readily loses its typicity.

Observed changes in wine region climates are well documented. During the last 30-70 years many of the world’s wine regions have experienced a decline in frost frequency, shifts in the timing of frosts, and warmer growing seasons with greater heat accumulation. In many cases these changes have brought more consistent vintages, while in others there have challenges with conditions that have been too warm and dry or brought more extreme or variable conditions. In North America research has shown significant changes in growing season climates, especially in the western U.S. where in the main grape growing regions of California, Oregon, and Washington, growing seasons have warmed by 1.6°F during the last 50 years, driven mostly by changes in minimum temperatures, with greater heat accumulation, a decline in frost frequency that is most significant in the dormant period and spring, earlier last spring frosts, later first fall frosts, and longer frost-free periods. These changes have allowed a region like the Willamette Valley of Oregon to go from a very marginal cool climate region in the 1950s to 1970s to one that provides much more consistent climate and vintages today.

To place viticulture and wine production in the context of climate suitability and the potential impacts from climate change, Figure 1 provides the framework for examining today’s climate-maturity ripening potential for premium quality wine varieties grown in different climates. 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 63°F and the climate warms by 2°F, then that region is climatically more conducive to ripening some varieties, while potentially less for others. If the magnitude of the warming is 4°F or larger, then a region may potentially shift into another climate maturity type (e.g., from intermediate to warm). While the range of potential varieties that a region can ripen will expand in many cases, if a region is a hot climate maturity type and warms beyond what is considered viable, then grape growing becomes challenging and maybe even impossible. Furthermore, observations and modeling has shown that climate change will not just be manifested in changes in the mean, but also in the variance where there are likely to be more extreme heat occurrences, but still swings to extremely cold conditions. Therefore, even if average climate structure gets better in some regions, variability will still be very evident and possibly even more limiting than what is observed today.

While global scale trends in wine region climates have found that warmer growing season climates have allowed many regions to produce better wine, future climate projections indicate more benefits for some regions and challenges for others. Climate model projections by 2050 for the world’s wine regions predict growing season warming of an additional 2.5-4.5°F on average with spatial analyses showing the potential for relatively large latitudinal shifts in viable viticulture zones with increasing area on the poleward fringe in the Northern Hemisphere (NH) and decreasing area in the Southern Hemisphere (SH) due to the lack of land mass. Within regions, spatial shifts are projected to be toward the coast, up in elevation, and to the north (NH) or south (SH). For a region like Oregon’s Willamette Valley changes of this magnitude could have an effect on it’s varietal suitability or cause changes in wine style. Figure 1 shows that the Willamette Valley’s climate over the last 30 years has on average been between 58-61°F, centered within the ideal climate for Pinot Noir quality and production. However, conservative projected warming rates of 1-3°F could push the region’s growing season climate outside what we know today as being suitable to high quality Pinot Noir.

Overall, winegrapes are a climatically sensitive crop whereby quality production is achieved across a fairly narrow geographic and climatic range. In addition, winegrapes are grown largely in mid-latitude regions that are prone to high climatic variability that influence relatively large vintage differences. On top of the knowledge of the climate structure and variability in wine regions worldwide are the projected rate and magnitude of future climate change which will likely bring about numerous potential impacts for the wine industry, including – added pressure on increasingly scarce water supplies, additional changes in grapevine growth timing, further disruption or alteration of balanced composition in grapes and wine, regionally-specific needs to change the types of varieties grown, necessary shifts in regional wine styles, and spatial changes in viable grape growing regions. While uncertainty exists in the exact rate and magnitude of climate change in the future, it would be advantageous for the wine industry to be proactive in assessing the impacts, invest in appropriate plant breeding and genetic research, be ready to adopt suitable adaptation strategies, be willing to alter varieties and management practices or controls, or mitigate wine quality differences by developing new technologies.

- Gregory V. Jones, Department of Environmental Studies, University of Southern Oregon

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 +/- 0.5-1.0°F are highly unlikely. The vertical bars represent the current (green) and conservative 2050 projected (red) average growing season climates for the Willamette Valley of Oregon. The figure and the research behind it are a work in progress and are used with permission by the author, Dr. Gregory V. Jones.