[Updated: 17th September 2019]
The visualisation technique of ‘small multiples’ is often used to communicate a simple message. The above example shows maps of temperature change from 1850-2017 – the overall warming trend is obvious even though the details are fuzzy.
Technical details: The HadCRUT4.6 dataset is used with anomalies from a 1961-1990 baseline period. An annual average for a particular grid cell and year is only shown if 6 or more months have data, otherwise it is coloured white. The colour scale runs from around -2.5C to +2.5C.
Other examples: NASA have made a similar visualisation for melting Arctic sea ice.