This video shows the locations of the weather (surface pressure) observations being used to reconstruct global weather and climate. Observations coverage (1851-2008) in version 3.2.9 of the International Surface Pressure Databank (that used in the Twentieth Century Reanalysis version 2c).
Videos like this can be a very useful tool in exploratory data anlaysis, understanding patterns in the data that we use, and may help us ascertain the need for certain model choices. For example, early in this observation history a majority of the data comes from shipping routes – but the shipping route locations depend on wind patterns which in turn depend on the surface pressure that they’re measuring! This might suggest to a modeller that care needs to be taken when considering how to model the locations of the ship observed data and some dependence between the observations and the locations may need to be explicitly modeled.