Grape (Vitis vinifera) composition is a weather-dependent determiner of wine quality. With changing climates, we can expect variation in wine-quality. To understand the extent of this we built path models to create a generalised Cabernet-Sauvignon grape quality model focusing on the total concentrations of six important molecular groups (sugar, pH, phenols, tannins, flavanols, anthocyanins). Path models statistically connect factors from input to output using a series of dependent models. As such, this modelling approach takes the output from one model and puts it into the next model as a chain. By varying climate inputs, we can simulate how changes in climate impact the final composition of the grapes throughout their ripening. We explore the impact of changes in composition under several climate change scenarios namely: changes in light, temperature, and rainfall by changing the climatic inputs to the path model. We find that, under moderate-projected climatic changes (a combination of RCP4.5 and SRES A2 and B2), we expect higher concentrations of sugars, lower acidity (a more neutral pH), and higher total concentrations of aromatic compounds (tannins, phenols, flavanols, and anthocyanins). We also find that an earlier start of ripening leads to the same result. These two results combined suggest the potential for stronger red wines in future, with more flavour-related compounds and in particular tannins which often give greater ageing potential.