Guest Post by Willis Eschenbach (see update at the end)
In England there was a recent partial collapse of the Whaley Bridge Dam. Of course, this couldn’t have been from, oh, I don’t know, bad construction or bad reservoir water-level management …
So naturally, the UK media is full of scary headlines.
The Whaley Bridge dam collapse is terrifying – but it will soon be dwarfed by far greater eco-disasters
Increasingly volatile weather due to climate change will mean events like these will become the norm. Unless we act to reduce our carbon emissions now.
Yeah, right … this totally ignores the facts that nobody has shown any correlation between rainfall and CO2 levels, and that climate models are notoriously bad at predicting precipitation … but I digress.
So I thought I’d take a look at the “increasingly volatile” rainfall that they are claiming. Here, from the good folks at the Hadley Centre, is the HadUKP monthly rainfall data for all of England and Wales :
No sign of the dreaded “increasingly volatile weather” in that data. But folks also say that although the total rainfall hasn’t changed, the individual storms are dumping more water. So I took a look at the daily rainfall data. It only covers back to 1931.
No trend there … so I thought I’d look at just the days with big rainfall amounts, those days with over a third of the maximum daily rainfall. Here’s that dataset:
In the daily, monthly, and daily largest precipitation data for England and Wales, the trend is less than 1 millimetre per century and is not statistically significant in any dataset …
Finding nothing, I thought that I should look at a smaller scale. The Hadley Centre also puts out regional rainfall data. The Whaley River Dam is located in the sector that Hadley calls “Northwest England”. Here are the corresponding three graphs for just Northwest England.
Again, there is no statistically significant trend in either monthly or daily data. I’m sorry, but I’m not seeing any sign of increasing rainfall, either daily or monthly, that would cause any increased risk of dam collapses.
This is a recurring problem with climate predictions. Me, I need to see some significant variation in the actual record before I say that something has changed and that as a result, the future well may be different.
But far too often, climate scientists and the media make statements about future changes that are not at all supported by the actual record.
In other words … for the time being, at least, I’d say that the dams in the UK are safe from rainfall risks … although management and construction risks are an entirely different question …
Best to all on a lovely quiet summer evening here in the forest, with a bit of smoke from a small forest fire a hundred and fifty miles north …
[Update] Steve Mosher pointed out in the comments that I hadn’t directly measured the “volatility” of the daily rainfall. I said if it were getting more volatile you’d see it in the daily records themselves … however, to cover all bases I went back and looked at the data. Volatility is measured as the standard deviation of the data. So I looked each year at the trailing 10-year standard deviation of the daily rainfall … here is that graph.
As you can see, the period with the greatest volatility is not the present, but the decade ending about 1990.
My thanks to Mosh for pushing me to put the last nails in the coffin.