Monthly Archives: March, 2014

Has The UK Had Exceptional Winter Rainfall Or Is It Just Weather As Normal?

The BBC Horizon programme on ‘Global Weirding’
Horizon : “Something weird seems to be happening to our weather – it appears to be getting more extreme.”

The BBC reports:
Dame Julia Slingo, Met Office Chief Scientist, said the variable UK climate meant there was “no definitive answer” to what caused the storms. “But all the evidence suggests there is a link to climate change,” she added. “There is no evidence to counter the basic premise that a warmer world will lead to more intense daily and hourly rain events.”

“We have records going back to 1766 and we have nothing like this,” she said. “We have seen some exceptional weather. We can’t say it is unprecedented but it is exceptional.”

So what constitutes exceptional weather?

Paul Homewood has analysed the figures extensively and those suggest that for the UK, the weather is doing pretty much what it has always done. His blog is available at http://notalotofpeopleknowthat.wordpress.com/

As a manufacturing engineer I was introduced to the wonderful world of control charts so I have constructed these to see if our current winter UK rainfall was exceptional.

The ASQ (American Society for Quality) suggests these criteria for an out of control process:

  • A single point outside the control limits.
  • Two out of three successive points are on the same side of the centreline and farther than 2s
  • Four out of five successive points are on the same side of the centreline and farther than 1s
  • A run of eight in a row are on the same side of the centreline.
  • Obvious consistent or persistent patterns that suggest something unusual about your data and your process.

When we look at the graphs below we see that in 2014 we have one point outside the Upper Control Limit, but looking at the previous years we see that the system was very much in control, the rainfall figures bouncing around the average, so is the Met Office basing its comments on a single data point? The figures also suggest that the period 1909 to 1930 was one of the most consistently wettest periods.

1767-2014 Winter precip

Winter Rainfall 1910-2014

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