coolinggap.eu: Europe is overheating, its cooling has not caught up

Every heatwave, Europe has the same argument. One side says air conditioning is an American indulgence we’ve done fine without. The other side points at the thermometer. Both sides argue mostly from memory, because the actual numbers are buried in national statistics portals, paywalled papers, and regulation PDFs that nobody reads voluntarily.

I wanted to know who was right. So I built coolinggap.eu and made it collect the receipts.

One rule

The site has a single editorial rule: no number without a source. Every figure links to the statistical office, paper, or dataset it came from, and where a trustworthy number doesn’t exist, the site says “no data” instead of guessing. It turns out “no data” appears a lot. That’s a finding in itself: for something people die of, Europe measures its cooling surprisingly badly.

There’s a country filter at the top, synced to the URL, so if you want to send someone the French numbers specifically, you send them coolinggap.eu/?country=FR.

Where the numbers come from

Temperatures were the easy part. Open-Meteo has a keyless API with current readings and the ERA5 archive going back decades, so a build-time script pulls monthly maximums for thirty countries since 2000, and CI refreshes the data on a schedule. No keys, no accounts, no scraping.

Everything else had no API at all. AC penetration, heat mortality, regulations, prices, surveys: that data lives in census reports and one-off studies, in half a dozen languages, so I curated it by hand into CSVs. To keep myself honest, a Zod schema fails the build if any row is missing its source name, URL, or date. I don’t get to ship a number I can’t back up, and not because I’m disciplined. Because the compiler says no.

(The site itself is Astro with React islands, Observable Plot for the charts, d3-geo for the map. Code is on GitHub.)

What I found

I expected a gap. I didn’t expect this one. In Malta, 84% of households have AC. Greece, 76%. Then you go north and the floor drops out: Germany 19%, the Netherlands 12%, the UK 4.3%, Poland 2.3%. These are places that now see heat that Athens would take seriously, with almost nothing to meet it.

The human cost is not hypothetical. Peer-reviewed estimates count 61,672 excess heat deaths in Europe in the summer of 2022, and another 47,690 in 2023. And the gap isn’t only about habit or climate: 38% of EU households say they cannot afford to keep their home adequately cool in summer.

The regulations page was the part that surprised me most. Spain caps public-building cooling at 27°C. The EU’s F-gas rules will ban new residential AC with high-GWP refrigerants from 2027. Some of these policies have good reasons behind them. But it’s worth seeing them listed next to the mortality table.

Go argue with sources

The site is live at coolinggap.eu. Pick your country, click the little source marks, and next time the heatwave argument starts, bring numbers. If you find a better figure than the one shown, the data is all CSV: fix it with a pull request.