Implications of a Climate-Changed Atmosphere on Cool Climate Viticulture

The impact of anthropogenic global warming on viticulture has been thoroughly studied. However, many of the climate projections are limited by the resolution of the models which cannot resolve mesoscale weather patterns, which heavily influence grape production. In this work, data was gathered from the National Center for Atmospheric Research wherein a high spatiotemporal resolution (4x4km, 1 hour) Weather Research Forecast (WRF) model was run from October 2000 to September 2013 over North America using observed data, and again using the atmospheric chemistry of CMIP5 ensemble mean of the RCP8.5 greenhouse gas emission scenario, creating a Pseudo Global Warming (PGW) model. Such models are capable of resolving the mesoscale influences that most climate models cannot. Contrasting the observed results to the PGW results allows users to compare “what happened” to “what could have happened.” This analysis was applied to four cool climate viticultural regions in the United States: two in Michigan, one in upstate New York, and one in Oregon. In the PGW-run, hours exposed to extreme heat (>32˚C) increase by orders of magnitude. Growing Season GDD accumulations increase between 783 and 1057 base 10˚C in comparing the models, while growing season average temperatures increase between 4.05˚C and 5.53˚C. Precipitation patterns were also studied. The four regions would no longer classify as “cool-climate” and would see growing seasons similar to some of the most productive warm-climate wine producing regions. The authors consider the opportunities and challenges presented by the potential climate shift for cool-climate, and warm-climate, viticultural regions.