Impact of climate change in Mexican winegrape regions

We analysed the current climate of seven winegrowing regions of Mexico and their possible changes during the 21st century. Various bioclimatic indices were calculated with observations and simulations over a wide domain that covers Mexico and the south and southwest United States. We used two regional climate models (RegCM4.7 and RCA4) for historical (1981-2010), near future (NF: 2021-2050) and far future (FF: 2070-2099) periods under two greenhouse gas emissions scenarios (RCP2.6 and RCP8.5). Both models reproduced the main characteristics of the Mediterranean and semiarid climates typical of the winegrape regions with some biases. Despite the errors, the models suggest similar future changes during the growing season (GS: April-October) in winegrape regions. Increases in temperature (similar to 1.2 degrees C) are expected in the NF, which could produce an early start from the growth (mid-March) season to the harvest. More significant changes are expected in the FF under the RCP8.5 scenario; temperature during April-October may increase similar to 4 degrees C, and growing degree-days (GDD) and minimum temperature could also increase (similar to 700 and 4.5 degrees C, respectively), especially in the northern Mexican high plateau, substantially reducing the suitable areas for viticulture. In Baja California (BC) the suitable years for viticulture may decline by 30%-50%, suggesting an increase in the interannual uncertainty. Moreover, in BC and California the number of cool nights (Tmin < 12 degrees C) could be reduced during the current harvest season (September) affecting winegrape acidity and flavour. Therefore, the viticulture sector and the wine industry may need to implement early adaptation/mitigation measures to overcome these possible changes and winegrape phenology shifts.