The simplest kind of weather station for KS1
Make pine cone weather stations with your class, and see how well they do at telling whether it is raining or not!
More experiments and demonstrations

Particulate Matter, ice, albedo and melting – Teacher’s Notes
Particulate Matter and aerosols are made up of a variety of pollutants, some of them enhancing and some counteracting the greenhouse effect when they are in the atmosphere.

Ocean Acidification – Worksheet
Increased CO2 levels in the atmosphere are buffered by the oceans, as they absorb roughly 30 % of this CO2. The negative consequences of this are that the oceans become more acidic.