Small particles in the atmosphere are usually hard to see and measure. But they are always present and have large influences in various ways:

1. The smallest particles can penetrate lung tissue and can cause health problems. Annually, over a thousand people in the Netherlands die early due to the consequences of particulate matter. Currently the fine dust can only be measured locally and there is little information about the composition of the particles and where they originate from.
2. Volcanic eruptions produce large ash clouds that can damage airplanes. The location and thickness of these clouds are difficult to measure and usually the entire airspace is then shut down. The volcanic eruption on Iceland in 2010 cost the airlines over a billion euros.
3. The largest unknown factor in the climate problem is the effect of dust and other aerosols in our atmosphere. Dust reflects sunlight and can form clouds that reflect even more sunlight, causing a net cooling of the atmosphere. But to what degree our climate is affected by this cooling mechanism compared to global warming due to greenhouse gases is yet largely unknown.

Below are links to texts on the influence of aerosols on the climate: KNMI; Climetepedia; IPCC