Aerosol

Tiny solid or liquid particles suspended in the air — dust, smoke, sea salt, sulphates, soot.

Why it matters

Aerosols scatter and absorb sunlight (cooling or warming climate), seed clouds, and degrade air quality. Measuring them is central to both health and climate science.

In plain terms

The haze you see on a smoggy or smoky day — countless particles too small to see individually, but together they dim the sky.