Sunday, May 16, 2010

Probably a poor chart

UK people will remember that in 2009, one of the rainiest summers in memory (and the third rotten summer in a row), the Met Office issues an optimistic press release promising "The coming summer is 'odds on for a barbecue summer', according to long-range forecasts".

This was accompanied by this bar chart, brought to my attention by Emma Hicks, a student on our MA Information Design course. She is doing a project with our meteorology department to suggest improvements to the way they express probabilities in forecasts.

Not only does it display 20%, 30% and 50% in the wrong proportions, but the hotter orange colour for the 50% bar makes it appear that a much more extreme difference in temperature is being forecast. Actually the predicted differences are less then 1 degree apart.

As it happens, the summer was warmer than average... the only problem was it rained all the time.

The Met Office has since announced they are dropping long range forecasts. They might want to look at their PR department at the same time.