It Never Rains But It Pours

Last month there was a brief (very brief) flurry in the mainstream media regarding a huge programme, using citizen volunteers, to digitise UK rainfall records going much further back in time than had previously been the case. The BBC headlined it with “UK’s rainfall records rescued by volunteer armyi, while the Daily Telgraph’s headline was “Weather history books rewritten as Victorian archives push back records by close to 180 years”ii, with a tantalising subisidiary headline: “A project digitising the Met Office’s archive has found that several records were set much earlier than previously thought”.

The Daily Telegraph article is behind a paywall, but much of it can be seen via Paul Homewood’s website, where it is reproduced under Paul’s article headed “Weather Records Shattered–180 Years Agoiii. It was all based on “Millions of historical monthly rainfall observations taken in the UK and Ireland rescued by citizen scientists”iv, whose lead author was Ed Hawkins, of the National Centre for Atmospheric Science at the University of Reading.

The Daily Telegraph article quotes Hawkins as saying things like:

A lot of the dry records that we’ve got have been rewritten, and that’s purely because our climate is getting wetter now.

Just like all the cold records are back in the past, it’s the same with the dry records, because the climate’s got wetter.

Most of the wet records are more recent – the exception to that was 1852 which was an extremely wet November, and I’m sure at the time they wondered what was going on.

That would be a stand-out month for that period. Now it wouldn’t look so unusual.”

The UK’s average temperature is thought to have risen by 1.5C since the pre-industrial period, he said, and the extra data “helps us better understand the long-term trends towards the dramatic changes we’re seeing today.

I found those comments to be rather odd, given the contents of the paper on the Royal Meteorological Society website, where the records were analysed. Having read it, I couldn’t see how those comments could be justified. Neither could Paul Homewood, who responded:

It is true that the UK is wetter on average

But this is largely due to Scotland. In England, the long term average has changed little since the 1870s

The major change is that drought years are very much a thing of the past, which in turn pushes up the average. This does not mean England’s climate is becoming more extreme, quite the contrary.

Now consider this Hawkins claim:

Most of the wet records are more recent”

When we actually examine the data, we find it is not only baseless, but grossly misleading.

Since 2002, only one year, 2012, makes it into the ten wettest.

And in terms of wettest months, only two months occurred in the last decade, January 2014 and February 2020. Given that there have been 29 months over 150mm since 1836, this is close to average

There certainly have been much more extreme interludes. For instance the 1860s, when three months made the list. Unquestionably the most extreme decade though was the 1910s, with five such months – 1911, 1912, 1914, 1915 and 1918.

1929 was also a remarkable year, with November and December receiving 173mm and 163mm of rainfall respectively.

The wettest month in recent years was November 2009, with 170mm. But that was only the sixth wettest month on record. By far the wettest was October 1903, with 191mm.

By every measure Hawkins claims don’t stand up to scrutiny, for England at least.

The dataset

My hope is that the dataset will be made freely available for online research, so that we may all be better informed regarding rainfall trends in the UK. And as regards claims that more recent years set any sort of record (whether wetter or drier) it’s worth bearing in mind that the number of rainfall “stations” where data has been maintained are much more numerous in recent years than in earlier ones. That alone increases the chances of records being set increasingly often in the modern era – but it doesn’t mean that they represent a meaningful “record” if no data for the “record” location was available in earlier years.

Although the information retrieved and digitised is voluminous, and the work is potentially of great value, we should always bear in mind that the earlier the dataset, the more restrictive it is likely to be (in terms of number of locations at which it was recorded). Despite that limitation, I think it is therefore extremely illuminating to note the following (quotes taken variously from the four articles referenced here, all of which are worth a read):

There is now a new driest year on record. This is 1855, with just 786.5mm of rain. It takes over from 1887

There is now higher confidence that the wettest month on record was October 1903, with 220mm of rainfall

The driest month for the UK is February 1932 with 9.5mm. Again, this record now has higher confidence

The project has better mapped big drought periods in the 1880s and 1890s; and in the 1840s and 1850s

New records include England’s driest May, originally thought to be May 2020 but now believed to be May 1844, when the country saw just 8.3mm of rain.

November and December 1852 were also exceptionally wet months, with the year seeing the wettest November on record for many regions in southern England.

1852 was also the wettest year overall for parts of the UK including Oxfordshire, where there was significant flooding.

A look at the graphs of annual seasonal rainfall in the UK from 1836 to date doesn’t appear to show any discernible trends. The same is true of the graphs showing England & Wales average seasonal rainfall from 1800.

On a lighter note

The problems of relying on some of the earlier data is set out in less serious language. A few examples:

Woolwich Eltham High Street, 1944: “Gauge destroyed by enemy action”.

West Ayton (North Riding) readings stopped in September 1949: “too old to bother now”.

Harter Fell, Middleton-in-Teesdale, November 1876: “no readings as gauge stolen”.

The Hall, Sunderland, 1866: “Rev Iliff (the observer) thinks his observations hopelessly wrong”, followed by a comment in 1869: “Rev Iliff had his right arm broken in June so was prevented from taking his observations regularly and a few weeks afterwards a road was made through his garden and his instrument meddled with”.

Saffron Walden Audley End (Essex) by J. Bryan (the observer), 1876: “I am afraid, there is not much dependence on this gauge… I find the funnel often unlevered (by) curious persons taking it off to see the inside”.

Sevenoaks Chevening Gardens, September 1892: “Gauge emptied by child”.

Stourmouth Rectory Kent, 1863: “Gauge found choked with a bird’s nest”.

Walden Head near Aysgarth, 1875: “Gauge destroyed by tourists”.

Dartmoor Chagford White Ridge, 1928: “Gauge disturbed by ponies”.

Perth (The Academy), 1936: “G. somewhat out of shape having been struck by lawn-mower”.

Banstead Mental Hospital, Dec 1951: “Gauge hidden by inmates.” (The record did not resume until July 1954.)

Leeds, Allerton Hall “site unsatisfactory. Obs refuses to consider new site. Blacklisted”.

Shotley Bridge, Durham “1894 Mr Coulson died in September & the record for the remainder of the year is unsatisfactory”.

Ingbirchworth, Brown’s Gauge, 1870s “From the record kept by the observer at the Reservoir. The observations are carelessly entered & the arithmetic is very faulty. In a few cases there is doubt whether small quantities were left in the gauge at the end of the month. Nevertheless the record is substantially correct”.

Conclusions

Thanks should be given to those who devoted time and energy during the first covid lockdown to transcribing and digitising the data. It promises to be a veritable treasure trove.

Endnotes

i https://www.bbc.co.uk/news/science-environment-60860397

ii https://www.telegraph.co.uk/news/2022/03/24/weather-history-books-rewritten-victorian-archives-push-back/

iii https://notalotofpeopleknowthat.wordpress.com/2022/03/26/weather-records-shattered-180-years-ago/

iv https://rmets.onlinelibrary.wiley.com/doi/full/10.1002/gdj3.157

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April 17, 2022 at 03:16PM

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