The pepper molecule
Syrah's signature black-pepper note comes from a single compound, rotundone. Crucially, it's higher in cooler conditions — so cool-climate Syrah (Northern Rhône, cool Australia) is markedly peppery, while hot-climate Shiraz leans to sweeter dark fruit and spice.
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Climate decides the accent
Same grape, two accents: cool = savoury, peppery, medium-bodied; warm = ripe, full, chocolatey. Knowing this lets you guess origin from the glass.