The impact of climate projections when analyzing the risk of frost to viticulture in the southern region of Brazil

Climate change is causing concern for agriculture, especially due to the occurrence of extreme air temperature and rainfall events. The aim of this paper was to evaluate the effect of the increase in air temperature predicted by climate projection models on the risk of frost in vineyards in the Southern region of Brazil (Paraná, Santa Catarina and Rio Grande do Sul). The frost risk analysis was based on the ten-day likelihood of minimum temperatures lower than 1, 2 and 3°C occurring (a more or less demanding criterion), considering the months of July, August and September. The results showed the effect of rising air temperatures in reducing the risk of frost. As expected, the higher the threshold, the greater the likelihood of occurrence. A lower probability of frost occurring featured for the month of September at the three thresholds, corresponding to the considerable warming that was forecast for this month. In Rio Grande do Sul, in the month of July the risks of frost occurring are greater, especially in the south of the state and in the mountain region. In the Mid and High Uruguay Valley and the Central Plain regions, the risks are lower and do not exceed 20%. In Santa Catarina, the greatest probabilities of frost occur primarily as a result of high altitudes and low valley regions. In the 1^st and 2^nd ten days the risks extended until the month of August. With these projections, it is concluded that early sprouting grape cultivars will suffer less damage from frost, favoring wine quality and productivity. In the state of Paraná, in both cases, A2 and B2, the results did not present risks greater than 20%.