Monday, 28 December 2015

Flooding in the NW - Is December's Rainfall 'Unprecedented'?

Unprecedented flooding, unprecedented river levels, even - according to Liz Truss, unprecedented rainfall. I thought I would take a look at the HadUKP data to see if the hype from the politicians matches up to reality. Short answer: not really.

Firstly, let's take a look at the December graph for England and Wales, which goes back to 1766 (2015 data is obviously not in yet as there are a few days to go).


What is obvious is that for the first 100 years after 1766, England and Wales were relatively dry for this month. Thereafter, it got quite a lot wetter in general. In 1876, the record for December rainfall was set. Since then, no December has ever been wetter. 2015 looks unlikely to beat the 1876 record of 194mm - it is 120mm as of Dec 26th.



We would need very heavy rainfall widely across England and Wales over the next few days for this record to tumble. But regardless of whether it does or not, it can be seen that, from the beginning of the 20th Century, there has been no clear upward trend in December rainfall in England and Wales. Indeed, if we look at the decade centred on 1910, we can see that this actually had the wettest run of Decembers in the entire period.

So, what about December rainfall in the North West?


Again, no overall increase discernible since about 1910. It is noticeable that from about 1907 to 1920, Decembers in this region were consistently very wet, hence the peak in the decadal average. It has been quite wet in the NW in December since 1980 - though not consistently so - and the record was set in the early 80's, which also might be broken by this year's very wet December. But 'unprecedented'? Hardly. The NW records only go back to 1873. If 2015 rainfall exceeds the early 80's record, it will only be 'unprecedented' within the last nearly 150 years and even then, a fairly isolated extreme occurrence.

Finally, let's look at winter rainfall in general, firstly in the NW:


Once again, we don't see much evidence of a definite trend throughout the last 100 years. The record wet winter for this region occurred about 1992. Will 2015 be wetter overall? Jan and Feb are yet to come. Watch this space. What about winter precipitation in England and Wales as a whole?


It's the same story really. No clear increasing trend in winter precipitation since the very wet period centred around 1910. 2014 stands out as a clear record though, but very wet winters would have to continue for a good few years yet for meteorologists to point to a trend and then for climatologists and politicians to tell us that that trend is anthropogenic in origin.

So, the data (inconvenient as it may be) doesn't match up to the climate change rhetoric being spouted by politicians looking for an excuse for a woeful lack of flood preparedness, plus the hype by green activists and their insistence upon bandying around their favourite term 'unprecedented'.