Annual Temperature Trends: More about the data

The above trends are based on monthly temperature data collected and archived by Environment Canada - the Adjusted Historical Canadian Climate Data. This database includes data from stations across Canada. Four stations were chosen to represent the different areas of Alberta: Fort Chipewyan to represent northern Alberta, Medicine Hat to represent southern Alberta, and Edmonton and Calgary to represent these major population areas. Stations were chosen on the basis of both location and length of the data series. Mean annual temperature values were used for this indicator.

The 30-year rolling average is an average taken over 30 years, which is calculated and plotted each year in a sequence. In this way, each point on a graph represents a 30-year average. The 30-year rolling average was calculated for each year based on the midpoint year. For example, the 30-year average plotted for 1986 is an average of the annual temperature values from 1971 to 2000. The midpoint year was used for plotting so that the rolling average trend would visually match the long-term variation in the annual trend line. In this case, the 16th year was chosen as the midpoint year of the 30-year time period.