Zoom from the planet down to the pavement. Inside a city, heat and green are the same map, inverted — and that mirror is the lever: greening the barest ground cools it, measurably.
Click a country to see its 40-year curve. The full interactive world grid (GHS-POP × comfort) is the next build.
The hot cells and the bare cells are the same cells. Across these cities the two grids correlate at r ≈ −0.8 — heat is where green isn't.
The slope of that mirror says how much each unit of green cools the ground. It turns "plant trees" into a number a city can budget.