Issue link: http://read.dmtmag.com/i/89494
ests could all be realized with one shift in my studies. V&WM: When people talk about climate change, they often focus on increasing temperatures. What are some of its other effects? GJ: Temperatures are the most about alcohol levels in wine? Are they higher today because of cli- mate change? GJ: This is a difficult issue talked about because they have trended more significantly, we have longer time series to work with, and they are more easily understood by the public. However, climates have been changing in terms of extremes as well – such as winter minimum temperatures, frost fre- quency and timing, high nighttime temperatures, and heat extreme events in the summer. Precipitation amounts have not changed to the same degree as temperature due to strong seasonal and year-to-year variability in most wine regions. However, we are seeing more of our annual precipitation coming in fewer, more extreme, events. V&WM: What effects can cli- mate change have on vineyard pests and diseases? GJ: Pests and diseases have two basic controls: weather/climate and people. Climate limits the geo- graphical distribution of vectors by controlling their lifecycle stages or number of lifecycles. Depending on the vector, changes in climate could bring about more rapid growth, more lifecycles per season or more synchronous or asynchronous relationships with other beneficial insects or plant growth stages. Dis- eases that impact vines are affect- ed by both in-season weather events (high humidity, optimum temperatures for development) and vectors. Clearly some pests and diseases have been altered over the last few decades due to changing climates, but more significantly they have been trans- ported by humans. This is likely to con- tinue into the future and with warmer climates, there are likely to be more areas where the risk will increase. V&WM: What WWW.VWM-ONLINE.COM NOV - DEC 2012 VINEYARD & WINERY MANAGEMENT 59 to address for a number of rea- sons. First, we really don't have any long-term (50 years or more) data on sugar levels and alcohol levels. The reason you need long- term data is that you need to test for the climate effect before and after the rapid warming of the last 30 years. From the limited data we have in the U.S. and some other data from Europe and Australia, it is absolutely clear that sugar levels at harvest are higher, acid levels have declined and alcohol levels in the finished wines are higher. This even holds in scientific obser- vation studies where the date of maturity is based on reaching a certain sugar level; in these studies the date to reach the level has trended earlier into a hotter period of the year.