Meteorologische Zeitschrift (Apr 2015)
Changes in phenology and frost risks of
Abstract
For a retrospective period of 110 years between 1901 and 2010 (observed data), and for the subsequent future period between 2011 and 2100 we calculated the phenological development (bud burst, harvest ripeness), and in particular the spring frost risk (frost after bud burst), as one important derived variable for grapevine (Vitis vinifera L. cv Riesling) for the whole of Germany. For the future climate we included two different scenarios (RCP8.5, RCP2.6) each of them containing a triple set with minimum, medium and maximum temperature increase. The time period between 1981 and 2010 as the last three decades in the observed data was chosen as reference. In general we found an acceleration of the phenological development (all main phases) mainly beginning in the late 1980s. For the three-decade period between 2031 and 2060 this acceleration will reach 11±3$11\pm3$ days in the RCP8.5-scenario. The acceleration for the other stages behaved similarly and results in an earlier harvest ripeness of 13±1$13\pm1$ days. Since a warmer spring in general leads to earlier bud burst, but does not reduce the risk of frost events during this period in the same manner, changes in the risk of spring frost damage were relatively small. For the coming decades this risk will not decrease for all traditional German viticultural regions in the RCP8.5-scenarios; on the contrary, our results suggest it is likely to increase. The results showed an increasing spring frost risk not only for the debated “upcoming” potential viticultural areas in eastern Germany, an effect which will partly also reach the southernmost viticultural areas. This effect in northern and eastern Germany is due to earlier bud burst together with the stronger continental influence, but for the southern and western regions of Germany is mainly due to the even earlier bud burst. This could modify the regionally nuanced character of German wines.
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