About This Data
Then versus now
Every fact compares the earliest five full calendar years on file against the most recent five, the same "then vs. now" window Climate Capitals' Key Findings already use. A capital with a shorter backfill still gets a fair comparison, since the window size shrinks to whatever's actually available rather than assuming a fixed 50 years everywhere.
Works in any climate
Every formula is a plain calculation with no special-casing per city, so it produces a sensible answer whether a capital has real winters or never sees a night below freezing, from Reykjavik to Nairobi.
What's cited
Each formula is a named, widely-used rule of thumb, not a bespoke model: concrete's thermal expansion coefficient, the USDA plant hardiness zone width, the Q10 rule for insect development speed, Clausius-Clapeyron for rainfall intensity, and more. The exact constant and its source sits in a comment next to each formula in the source code, the same transparency principle Climate Transition uses for its ranking.
