Temperature Anomaly: what is it, how is it used?

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A temperature anomaly is the difference between the current temperature and the long term average.  A positive temperature anomaly indicates that it is warmer that the long term average.  Likewise a negative anomaly indicates that it is cooler than the long term average.

Temperature anomaly is dependent on the period being used.  The average temperature over the last 10 years may differ from the last 100 years, and would give us different anomalies for today.  For example, the annual global mean surface temperature published by NOAA (National Oceanic & Atmospheric Administration) is 13.9 degrees celsius.  This is based on average temperatures between the years 1901 and 2000.  The annual temperature anomaly for 2014 is 0.74 degrees and the latest monthly anomaly is 0.98 degrees (October 2015, at the time of writing).  This means one published anomaly cannot be directly compared to another.

Historical temperature anomaly is shown on the following chart, monthly anomalies shown by the jagged blue line, annual anomalies by the red line.  Note also on the right hand side of the chart, the future upward trend over the next 5 years.

temperature anomaly chart

Monthly and annual temperature anomaly for the period 1980-2015. Data source: NOAA

In practical terms, how is temperature anomaly calculated?  Temperature readings from an extensive set of locations are collected and an anomaly is calculated per location and then averaged to give a global temperature anomaly.   For example NOAA’s approach is to use a 5o x 5o grid across the earth’s surface, and area-weight the anomaly for each grid square.

How is it used?  Temperature anomaly is used as one of the means to measure climate change, by providing a big-picture overview as to how much warmer (or cooler) the average temperature of the earth is getting.

Read on to find out how temperature anomaly is used by PAL’s carbon pricing app.


Edward Coe

Author: Edward Coe

Edward Coe is Managing Director and co-founder of PAL. He has extensive experience of systems development and implementation for advanced derivative trading systems utilising a broad range of technologies supporting in house, bespoke and third party software. Edward developed the software behind PAL Carbon.

Temperature Anomaly: what is it, how is it used? was last modified: August 8th, 2017 by Edward Coe