The project "Clim4Edu" brings Climate Change and Earth Observation together for secondary education. Two interactive tools have been created to convey how modelling of atmospheric components based on satellite data works. The CO2 concentration has changed over the last couple hundred, thousand, hundred thousands of years based on multiple measurement techniques.
Check them out at https://fis.rub.de/klimawandel !
For now, the materials are only available in German, but an English version is in the works.