1.1 Time series
Below is a very ‘busy’ graph intended to demonstrate the increase in global temperature over time. There are two time periods represented here – working horizontally, each line shows the change in average temperature (read on the left vertical axis) across the period of a year while the colour chart on the right shows that each line represents a different year.
This graph was published as part of a Met Office news item entitled 2023: The warmest year on record globally - Met Office. Taking examples of data presented in the news is one way to help bring data to life for learners.
One line on the graph in Figure 1, for instance the red line representing 2023, is an example of one time series. It represents the shape of the data or the trend of the data over one year. If data is collected repeatedly for the same length time period, as is the case here, it may be possible to identify patterns in the data and perhaps even make predictions or forecasts about future time periods. It is these forecasts that make the use of time series graphs appealing to meteorologists, investment bankers and political parties.
A time series graph is a line graph.
The key point from a learner perspective is that these graphs are intended to show a trend over time which is why the line is formed by joining the value from one point in time (here each month) to the next. In this example, the vertical placing of the colour chart does also draw attention to the overall rise in global temperatures over time.