A grape is a weather diary. How much rain fell in April, how hot July got, whether frost hit in September, how intense the midsummer sun was — all of it gets encoded in the grape's sugar, acid, tannin, and hundreds of other compounds. A sommelier tasting a wine is reading that diary.

This is terroir, a French word with no English equivalent. It means 'the sense of place' — but scientifically, it's measurable. Cool years produce grapes with more acid, lower sugar, brighter flavors, less body. Hot years make the opposite: ripe, jammy, high alcohol. A drought year concentrates everything. A wet year dilutes. Specific temperature windows at specific ripening stages create specific compounds. The year 2003, Europe's brutal heatwave, produced wines still easily identifiable decades later — baked, pruny, high alcohol.

The soil matters too. Calcium-rich limestone pulls water up through the roots via capillary action, stressing the vine and concentrating flavor. Volcanic soil adds minerals — some wines from Mount Etna genuinely taste of the mountain. Clay retains water; gravel drains. Two vineyards separated by 50 meters can produce wines that taste like different species.

And then there's the yeast. Wild yeast native to each vineyard has its own metabolic quirks, producing different esters and aromatic compounds during fermentation. Burgundian wines taste the way they do partly because of yeasts that live, ambient, in Burgundy's cellars and nowhere else.

When a wine critic writes 'this is a cool year from a limestone slope, fermented with indigenous yeast,' they're not being pretentious. They're reading geology, meteorology, and microbiology — compressed into liquid. Every bottle is a forensic sample.