Thursday, February 28, 2019


Antti Lipponen of the Finnish Meteorological Institute has created an animated chart that shows the trend in global and national temperatures from 1900 to 2017, ie almost to the present day. The distinctive feature is that it shows how an overall trend, significant in itself, can mask even more dramatic swings in individual geographies and in variations between them. Some though not all of these are likely to be experienced as episodes of unusual or extreme weather, eg drought or flood.
It is expressed in terms of temperature anomalies, or deviations from the norm. In this case this just means deviation from the average over the period 1951-1980.
To interpret what is happening in more detail, the following is a useful key
Year. In the centre of the circle is the year of the observations, starting in 1900.
Global temperature trend: top right of the picture.
Temperature anomalies.   Moving out from the centre are five concentric rings, corresponding to the size of the anomaly: from – 2.0oC through –1.0oC, 0.0oC, +1.0oC, to +2.0oC. Individual country values are expresses as spokes emanating from the centre, with colours expressing the scale of the deviations, (negative = blue, positive = red)
Geography. The individual countries should be visible in full screen mode, but for a quick impression of what is happening in global differences, note that the quadrants can be summarised as follows. Moving clockwise from 12.00, we find:

Top right; Asia and the Middle East
Bottom right: Africa
Bottom left: Europe
Top left: The Americas and Oceania

The animation has the virtue of demonstrating in visual form the potential significance of global warming in provoking increasing numbers of extremes, which may nevertheless vary substantially from year to year, country to country, and continent to continent.

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