Global Chilling Projection - Overview

Many tree crops that are commercially grown today originate from cold-winter climates in Central Asia and the Middle East. Because of harsh winters in these areas, trees fall dormant in the winter to avoid frost damage to sensitive growing tissue. During winter dormancy, most physiological functions are suspended or severely slowed. To resume growth in spring, winter dormancy must be broken, and trees have evolved sophisticated mechanisms to detect the end of winter. They monitor the progression through the cold season by recording how long it has been how cold. Duration and 'amount' of coldness is integrated into winter chill, and trees are only receptive to warming in spring, after they have fulfilled their chilling requirements. This chilling requirement is thus a major factor that determines where certain tree species can be cultivated. Chilling requirements constrain the suitable areas of many commercially important tree species and cultivars around the world.

According to climate model projections, global temperatures are likely to rise during the 21st century, and this is likely to affect winter chill in many growing regions. This in turn may shift suitable ranges for commercially cultivated tree crops. Due to the long productive life spans of trees, anticipating future winter chill can be crucial for ensuring that the current high level of productivity can be sustained in the future. This website therefore provides winter chill projections for several climate scenarios, including historic changes, as well as changes projected by global climate models.

The full methodology is published here (freely accessible):

The information presented in the paper and citations for all background information, as well as the dataset available from this website, can be used for any non-commercial purpose, but please ensure that the following reference is added in any derived work:
Luedeling E, Girvetz EH, Semenov MA and Brown PH. Climate change affects winter chill for temperate fruit and nut trees. PloS ONE 6 (5), e20155.

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