Saturday, 1 March 2014

UK Floods In Context

I am tempted to make some cutting comment about those who indulge in games of 'look squirrel' and those who publicise them, but such people bore me.

There are times when only a simple graph is needed.

Data from here.


Snial said...

I think the simple graph is meant to show that there's no correlation.

Ironically, in my blog from late January "Rain rain, won't go away" my application of Met office data does draw an indication of increased rainfall for the months in the year where flooding took place in 2012 and also for the recent rainfall events in 2013/2014:

Chris Reynolds said...


Sorry, you misunderstand, it's not meant to show that at all.

Time goes up from 2010 to 2013, the amount of rainfall each year is from low rainfall on the left, and high on the right. Use the 1000 and 1200mm markers as a rough guide, rain lower than that is for the dryest years, higher is for the wettest. Now follow up the graph (forward in time) and see what happens after around 2000.

After 1998 the wettest years have been wetter leading to an increased variance and an increase in the amount of rainfall when years are wet.

The UK has been experiencing wetter weather and more variable weather (in terms of rainfall).

I'm working on it at the moment but strongly suspect that the key factor is the increase in SST in the Atlantic as the AMO went positive around 1998. However this is massively amplified by the warming of the oceans due to AGW, which is why we don't see the same pattern in the earlier warm phase of the AMO.

Snial said...

Hi Chris,

Thanks for that. You're right of course, the graph does show that. I had noticed when I first looked at it that the highest rainfall years were since 1998 except for 1953; which represents a ratio of 5:1 and as one looks at lower rainfall years gradually the ratio decreases (e.g. for rainfall >about 1250 it's 6:3 in recent years).

This correlates well with Hansen's work on how climate change 'loads the dice': the 'expected' distribution becomes distorted towards the more extreme results.

My blog entry only covers individual months, because I had naively accepted based on anecdotal claims of the kinds you link to the annual rainfall distribution hadn't noticeably changed, but that monthly distributions could have: with some becoming wetter and others drier. My blog entry shows that, but I never bothered to list all the months. I also wasn't really aware of your position on UK attribution since so far I've only heard there are no attribution studies for the UK as yet.

So, thanks for the reply. Nevertheless I think lay readers will need a bit of help in decoding what the graph is saying, because at first glance it looks too close to a scatter graph to show a trend (at least to my eyes, though I identified the trend with a little effort).

-cheers from Julz

Chris Reynolds said...

Sorry, yes this isn't really a lay-readers blog. I tend to go a bit into detail and assume graph reading that isn't the average for the public.

Yep, baseless crap spouted by the sort of idiots who don't really dig into the data irritate me. There clearly is a shift in UK rainfall and there's science starting to back it up. This is just the start of a pattern that will become all the more strong in years to come.

Keep up the blogging. You might want to look at UK summer rainfall, particularly the clustering of 2007, 2008, 2008 and 2012 in the top ten wettest years.

Chris Reynolds said...
This comment has been removed by the author.
Nightvid said...

PIOMAS has updated!!!