How do you know how plants will respond to changes in climate? You try them out in different conditions to see how well they grow in a less than ideal climate and see whether or not they survive. Here is an interesting story from Atlas Obscura describing one testbed at the Wolfskill Experimental Orchards in California and how it is testing different varieties of nut and fruit trees to see how they stand up to long periods of droughts without supplemental water. Of course, just because the trees survive that does not mean they will provide a good commercial crop, because they could shut down their production of nuts or only make very small ones that are not good for sales. The article also discusses the impact of warmer winters on the physiology of the trees and how fewer chill hours is likely to not only reduce the yield of the plants but also decrease the health of the trees overall.