Abstract
AbstractA statistical analysis was conducted on long-term climate records in the Okanagan Valley wine grape growing region of British Columbia, Canada. No observable trends for average annual temperatures were found in the region. Analyses of monthly mean and extreme temperatures show wide spatial and temporal heterogeneity, indicating that future studies using downscaling of global climate models for this region will require resolutions on the order of several kilometers. Mean winter temperatures are increasing throughout the valley, and extreme minimum temperatures are also increasing during the winter at the central and northern sites which have historically presented the most risk of winter damage to grapevines. Only the most southern and northern sub-regions are expected to see significant changes in their heat unit accumulations during the growing season. Over the coming century, the southern end of the valley will likely move from Winkler heat unit region 1 to 2. All regions of the Okanagan will continue to have latitude-temperature indices among the lowest of the world's fine table wine producing regions over the coming century. Growing season and dormant season average temperatures are expected to change by only a modest amount by 2100. Current climate maturity groupings for ripening grape varieties will likely stay constant at cool (central and southern areas) and intermediate (south-central) for all sites except Osoyoos (south). The climate trendings at Osoyoos suggest it will transition from an intermediate to a warm grouping by about 2050. The early to mid-season ripening capacity of the region may improve due to climate changes, but there is a risk of the asymmetric late season increases in minimum daily temperatures lowering the daily temperature range at some sites, possibly leading to difficulties in maintaining a balanced between sugar and sensory profiles as wine grapes approach maturity. The projected warming at the southern end of the valley should favor improved and increased Merlot production, will require Chardonnay production to shift northwards, and will allow growing of warmer climate wine grape varieties currently inaccessible because of low winter temperatures and a lack of growing season heat units. Increasing winter temperatures throughout the region are expected to result in increased risk of pests such as Pierce’s disease.
Highlights
Concerns over global climate change have led to a critical examination of its potential impacts on agriculture during the past several decades
A distinct climate gradient exists in the Okanagan Valley, with average annual temperatures over the 1971-2000 period declining from 10.1°C at Osoyoos in the south to 7.4°C at Vernon in the north (Table 1)
The available climate record at these major stations throughout the Okanagan Valley suggests there are no observable trends for average annual temperatures in this wine grape growing region
Summary
Concerns over global climate change have led to a critical examination of its potential impacts on agriculture during the past several decades. In the United States, for example, previous work has suggested that extreme heat impacts may reduce premium grape production by up to 80% in the late 21st century. These heat accumulation increases are predicted to shift production towards warmer climate varieties and/or lower-quality wines while reducing the impacts of frost damage, but the increase in extreme hot days (>35°C) may eliminate wine grape production across much of the United States (White et al, 2006). Since many of the world's grape growing regions are located in semi-arid environments where water scarcity is a major scientific and political issue, increases in irrigation demand to offset the harvesting of hot, desiccated fruit may not be possible
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