Unexplained variation in data is not always 'noise'. It can be interesting in its own right, especially when we are interested in predicting the future. If we can assume that there will be no systematic change to the process that generated the observed values in our data,
... the proportion of times that an event happened in the past indicates the chance that it will happen in the future.
Annual rainfall in Oxford
For countries that are susceptible to drought, the variability in past weather records might give information about:
This information can potentially help farmers decide which crops to plant and when to plant them.