I AM SURE that I am not alone in my dubiousness over the way that mainstream media (MSM) have developed the art of typifying heavy rainfall as a disastrous calamity and proof that we are suffering a climate catastrophe. Quite fortuitously, I discovered recently that in a nearby village, someone has been assiduously taking measurement of daily rainfall, using a standard five-inch rain gauge. Measurements are made at 9am each day. The site has been inspected and approved by the Environment Agency, and it satisfies the Met Office criteria for site exposure. The collected data are archived by both these government agencies. Thus, they are bona-fide and official; they are facts. Therefore, I thought that I would carry out some simple reviews of what these data reveal.
I started by noting the occurrence of days (each day is recorded from 9am to 9am the following day) in which the total rainfall exceeded 25mm (approximately one inch). I have noticed that the MSM frequently reverts to the imperial system of measurement, despite the efforts of Harold Wilson’s government to introduce the metric system in the 1960s. This was part of forging a new Britain in the white hot heat of technology, I suppose. Having been part of that revolution in sixth form and at university, I am familiar with both systems, so unlike the MSM target audience, I can’t be baffled by numbers taken out of context. Here is a table of the rainfall events which reached the key values in each year since 2008:
DAYS WITH HEAVY RAINFALL, KERSEY 2008 – 2023
(Larger PDF version here).
The first thing to notice is the number of days on which the rainfall does not reach the threshold, and there is no clear pattern to this: no heavy rainfall days have occurred in four of the 17 years of record. There were a number of years where two or more heavy rainfalls were recorded, the most being in 2012 when there were three events. The highest measured rainfall on a calendar day was 49.1mm in 2016. I have also given a two-day rainfall, by including the rainfall total of the preceding or following day, as appropriate. This is a standard procedure to arrive at a representative value for a 24-hour rainfall. This practice recognises that the artificial imposition of 24-hour period, defined by the clock, may split a rainfall event over two calendar days.
In East Anglia, the occurrence of continuous rainfall, spanning more than two days, is negligible. The maximum two-day rainfall is 57.2mm; a check against the official Met Office estimate for the locality of the one-in-five-year value of 47mm would confirm that the record at Kersey fits the general pattern. The two-day total rainfalls again are variable, and have no perceptible variation in trend over the range of years for which the record is available.
The time of year at which these annual maxima occur is interesting. There is a bias towards spring/early summer and autumn, which presumably reflects the contrasts of the contributing air-masses at these times. There is little indication that the maxima have been affected by increased winter storminess and summer heat: the much propounded “warmer, wetter winters; hotter, drier summers” mantra of climate change orthodoxy.
In recent years, there have been two major storms near Kersey, which were summer storms, but very localised and producing extremely large falls*. The first of these events occurred on August 16, 2020 over an area of Breckland, producing 197mm in two and a half hours at Little Hockham, north-east of Thetford. The other event took place on July 25, 2021, centred on Brettenham, about eight miles NE of Kersey, and recorded 181.3mm in one hour and two-thirds. Both these events were highly localised, and did not feature as a heavy rainfall at the Kersey gauge, which brings us to the question of how representative the rain gauge network is.
There are no hard and fast rules on the density of rain gauges, and the location of gauges is as much dictated by the availability of sites, and the presence of willing observers, as anything scientific. The decline in the number of rain gauges in the ‘official’ network has been going on since the peak of over 5,000 was reached in the 1980s. By ‘official’, I mean those registered with the Met Office with regard to the type of instrument, the suitability of the site and the reliability of reporting. Although data records are primarily maintained by the Met Office and the Environment Agency, searching for data of a given date and location is not necessarily straightforward, although it was not always this way.
British Rainfall was an annual publication produced by an independent organisation from 1860 to 1968, and it served as a reliable and unified source of rainfall information from public authorities, private observers, etc., also producing reports of major events. Though it ceased independent publication in 1968, to continue in a stuttering way until the early 1990s. Published by the Met Office, its unparalleled record was used to provide a definitive list of 63 extreme storms as part of the Defra study for dam safety, by me and my colleague from the Met Office, Peter Dempsey (2009). The events listed below are taken from that list, and provide a good summary of the range of durations that extreme rainfall events can take.
MAJOR RAINFALLS IN NORFOLK AND SUFFOLK 1873-2000 FROM ‘BRITISH RAINFALL’
The two local rainfall events of 2020 and 2021, which I have mentioned previously, would have slotted nicely into the above table.
I hope my discussion has illustrated that extreme rainfall events are not new, and certainly not an unprecedented development: they are just in the nature of the beast. Why all the fuss when these events occur and flooding, localised or widespread, occurs? I would suggest that reporting such events as part of the ‘climate catastrophe’ serves at least two purposes. Firstly, without reference to past events, the media reports raise the necessary state of alarm amongst the general public to keep promoting the Government’s environmental projects. Secondly, they ignore the fact that floods, especially those on minor and urban roads, occur primarily because of poor design and even poorer drainage maintenance. Perhaps, the money that could be saved by abandoning publicity campaigns and promoting ‘green’ methods in the workplace could be used to dredge rivers, de-silt road drains and make effective designs for integrated urban drainage.
Acknowledgements. I am grateful for the supply of data to Mrs Kate Banks, observer, and Mr Neil Klotz, Hydrometric Officer, Environment Agency, Ipswich.
*These events were analysed in detail from a meteorological, hydrological and storm probability viewpoint, in collaboration with Dan Holley (Met Office) and Colin Clark (Independent Consultant), and were published as articles in the Royal Meteorological Society’s monthly publication, Weather.
