Thursday, 30 January 2014

Rain, Rain Won't Go Away

A couple of weeks ago I thought the UK was starting to turn a corner in recognizing the possibility that our weather is being affected by climate change. The connection between climate change and extreme weather reporting had declined in the 3 years from 2009 from 25% to about 11% in 2012, despite the extensive floods we had that year.

2013 had Century-level floods in Eastern Europe, India, China, Russia, Canada and Oregon but we were largely spared. However, in October however we had the worst storm since 1987; followed by the worst storm surge in 60 years; followed by persistent flooding in Scotland and Southern England over December along with a second storm surge that destroyed Aberyswyth's sea front and caused extensive damage elsewhere.

Since then parts of the country have had continual flooding to the extent that by early January David Cameron was admitting this could be due to climate change; which was backed up by the MET office which called for attribution studies to prove it.

But then at the end of January it was suddenly all put down to not dredging rivers. If that's true, then failing to dredge the River Severn has lead to Jet Stream blocking patterns and our wettest January on record.

So, I decided to take a look at MET office rainfall anomaly images for both 2012 and the end of 2013. I'm picking selected months. Let's see them:
April 2012 vs 1961-1990 April 2012 vs 1981-2010
June 2012 vs 1961-1990 June 2012 vs 1981-2010
July 2012 vs 1961-1990 July 2012 vs 1981-2010
August 2012 vs 1961-1990 August 2012 vs 1981-2010
October 2012 vs 1961-1990 October 2012 vs 1981-2010
November 2012 vs 1961-1990 November 2012 vs 1981-2010
December 2012 vs 1961-1990 December 2012 vs 1981-2010
The above images are for 2012 and tell us some interesting things. Firstly, the three months April, June and July were exceptionally wet. You can see how blue the country is. Secondly, the comparison with 1961-1990 is almost always bluer than 1981-2010. This gives us an indication that the UK was wetter over these months in 1981-2010 compared with 1961-1990. That's because the corresponding months in 2012 are less wet when compared against the more recent range. Now let's look at the flooding in 2013:
October 2013 vs 1961-1990 October 2013 vs 1981-2010
November 2013 vs 1961-1990 November 2013 vs 1981-2010
December 2013 vs 1961-1990 December 2013 vs 1981-2010
Again, we see the same sorts of patterns. We can see how extremely wet October 2013 has been (compared with October 2012). We can also see how the rainfall pattern has been so much more damaging in December 2013 compared with 2012 even though December 2012 looks generally bluer. Finally, also note that November has been getting wetter according to the graph, since November 2013 is relatively dryer compared against the 1981-2010 range vs the 1961-1990, i.e. 1981-2010 was a wetter period.


These images could tell us a couple of important aspects about climate change in the UK:
  • It's generally getting wetter for certain months in the year since the range 1981-2010 is wetter than 1961-1990.
  • We've been seeing some pretty bad weather: all those blue regions tell us it really has been getting worse.
  • Flooding can't just be due to a lack of dredging in the river Severn, because we're looking at pictures of rainfall, not flooding and these images easily explain why it's been so bad.


At the time of publication it wasn't possible to report the images for January 2014 as they hadn't been published by the MET. It is possible now. You can see the same trends are in effect: the anomaly for January 2014 is astonishing in both cases, but less so compared with the average rainfall over 1981 to 2010 (which implies that that period was a bit wetter than 1961 to 1990). In early March it should be possible to add the graphs for February rainfall (which won't be as extreme).

January 2014 vs 1961-1990 January 2014 vs 1981-2010

 Edit 2

And a day later the March 2014 data became available. Again, the same trends are evident. Firstly, Rainfall for the month is extreme - in fact more extreme than January and more extreme than I anticipated just yesterday as it covers Northern Ireland and Great Britain with the exception of the east coast and the North West of England. Secondly, rainfall is less extreme relative to the 1981 to 2010 period which means that that period is wetter. Truly astounding.

February 2014 vs 1961-1990 February 2014 vs 1981-2010