The Dust Is Piled, Not Spread

You'd think airborne dust would smear across the planet like weather. It doesn't. Right now, almost the entire inhabited world breathes essentially none — and nearly all the dust on Earth is heaped into a thin chain of desert-margin squares: the Sahara, the Sahel, Arabia, the deserts of inner Asia. It isn't a gradient. It's a switch. A handful of grid cells hold half of all the surface dust on the planet, this hour.

Switch the map to combustion smog — fine particulate, PM2.5, the soot of engines and stoves and industry — and the lit squares jump continents. The dust belt goes dark; northern India, eastern China, the cities light up instead. Two different dirty airs, two opposite geographies. Dust is geology: it comes from where the ground is bare and the wind is hard, the desert margins, mostly far from anyone. Smog is us: it pools where people burn things, which is where people are. And smog spreads more evenly than dust ever does — by this same count, it takes — squares to hold half the world's PM2.5, against just — for dust. The dust is the more extreme hoard.

Why does dust pile instead of spread? Because the heavy stuff falls fast. Coarse mineral grains lofted off a desert settle back out within hours to a day or two unless the wind keeps lifting them — so the high readings cling to the source. (The exception is the fine fraction that rides up into an elevated layer and crosses oceans without ever touching the surface — that's the Saharan dust bridge, a story playing out overhead right now while the sea below reads clean.) What you're looking at here is the opposite end: dust at nose height, where it's breathed, and at nose height it stays home. The single most prolific source on the planet is one dead lakebed — the Bodélé Depression in Chad — funnelling pulverised ancient lake silt into the wind. Most of the squares glowing on this map sit downwind of a desert like it.

How this was built. Live surface concentrations from the Open-Meteo Air-Quality API (Copernicus CAMS global model, no key, fetched in your browser on load), sampled on a global grid of — cells at 8° latitude × 10° longitude, from 70°N to 50°S. “Airborne dust” is modelled mineral-dust mass in the surface air (µg/m³); “combustion smog” is PM2.5, fine particulate from burning. The headline counts are computed live from the fetched grid: cells are ranked by dust, and we report how many top cells it takes to reach 50% and 90% of the total; “near-zero” is the share of cells under 1 µg/m³. A coarse grid undercounts narrow plumes, so the worst-square value is a floor, not the planet's true peak — point sources like Delhi can read several times higher. The dust field shifts hour to hour as winds rise and fall; reload for a fresh reading. Coastlines for reference only.