The Wonderful Issues of Climate Change - Post #4 - Graphing Climate Change

Original Date: January 10, 2024; Revised February 25, 2024

Author: Tim Platnich

This post will deal with the presentation of temperature data in graphics. I will talk about graphs showing absolute temperature change and graphs showing temperature anomalies. I will also talk about 'scary' graphs.

The above graph shows absolute temperature change from the 1880s to the 2000s. Notice the y-axis is graduated in 2 degree C intervals.

The above graph is dealing with the same data except that it shows 'anomalies' relative to a baseline. In an anomaly graph, a base line temperature is established, then temperatures for each year are shown relative to the baseline. Note the y-axis in this graph is graduated in .2 (point 2) degree C intervals.

When considering a temperature graph, keep in mind what the graph is actually saying - is it absolute temperature or temperature anomaly.

Colours matter. Following is a map showing temperature anomalies in October, 2019. Note the neutral range of colours showing anomalies between -9.5C and plus 9.5C.

Following is another colour map showing anomalies.

Note how the above graph uses extreme colouring to suggest that the arctic is burning up. In the first graph above, an increase of 4C is shown as a light orange colour. In the graph immediately above, an increase of 4C is shown as burning red. This graph is from Wikipedia. This is an anomaly graph, although it doesn't say that specifically. I am reproducing this graphic to illustrate how colour is used to display data. I am not sure that the data depicted in the Wiki graphic is accurate. I do note that the baseline used in the graphic is from a time of notoriously low temperatures - remember the global cooling scare! Also, the graphic compares a 10 year period - 2011-2021 with a 20 year period. Is this a fair comparison and depiction?

The lesson to be learned - don't be influenced by colouring. Be careful to read what the colours represent and consider the actual data. Also, with anomalies, carefully consider what time period is used for the baseline and what time periods are being compared.