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Long Term Rainfall Trends In England & Wales

February 17, 2014

By Paul Homewood

 

As promised, an update on precipitation trends from the England & Wales Precipitation Series , dating back to 1766.

First the annual trends, with a 10-Year Running Average.

 

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It’s a bit like reading tea leaves, and I have no doubt we’ll all read different things into this. But for me, the following things stand out:

  • 2012 was the wettest year in recent times, but only ranks third since 1766. The wettest year was 1872, followed by 1768.
  • Last year, at 917mm, was only 2mm above the mean for the period.
  • The current 10-Year average is not high by historical standards.
  • The 10-Year average hit a recent peak of 994 mm in 2002, but the wettest 10 years ran from 1874 – 1883, averaging 1017 mm a year.

Any sign that rainfall is on the increase? Not for me.

 

Seasonal Trends

I thought it worth looking at seasonal trends as well.

In the past, they often looked at “six month” winters and summers, i.e Oct-March, etc. This seems much more relevant than using traditional seasons, as in the UK at least, Oct/Nov/Dec/Jan tend to be the wettest months.

It is also common practice to use “hydrological years”, which begin in October. Clearly the concept of a traditional autumn season is meaningless for this.

Again taking the England & Wales series, for “winter” we get:

 

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  • There seems to be a shift change to wetter winters from around the mid 19thC.
  • Since the start of the 20thC, the trend is pretty much flat, albeit with a dip around the mid 20thC.
  • The last winter of 2012/13 finished with 656mm, ranking 11th wettest.
  • The wettest was 2000/01 with 809mm.
  • Next wettest was 1929/30, with 715mm.
  • The wettest 10-Year spell was 1994-2003.

 

And “summer”.

 

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  • The trend in the first half of the record is reversed, i.e summers tended to be wetter till about 1890.
  • The dry spell during the 1970’s is again evident, since when summer rainfall has recovered to levels common in the first half of the 20thC.
  • Last summer totalled 328.1mm, ranking 26th driest.
17 Comments
  1. February 17, 2014 4:11 pm

    Thanks. This puts it all into perspective. Great blog.

  2. February 17, 2014 4:36 pm

    Reblogged this on CraigM350.

  3. February 17, 2014 4:43 pm

    Paul, back in the eighteenth century, were there many monitored rain gauges distributed across England & Wales?

    Or, is the data a prolonged record from a single location?

  4. welshguru permalink
    February 17, 2014 5:31 pm

    I wonder what we would see if we were able to reach back another 199 years.

  5. winter37 permalink
    February 17, 2014 7:27 pm

    To welshguru: go to booty.org.uk for UKweather back to AD784.What we are seeing now is nothing to what our ancestors went thru.Not many rainfall measuerments,but the many months of nonstop rain should give an indication.

  6. Neil Hampshire permalink
    February 17, 2014 8:58 pm

    I am using Met Office ranked data for England and Wales
    http://www.metoffice.gov.uk/pub/data/weather/uk/climate/datasets/Rainfall/ranked/England_and_Wales.txt
    The table below shows the total winter (dec.jan.feb) rainfall for each decade.

    The period 1910-1919 is the clear “winner”. Long before modern AGW.

    Decades Winter
    1910’s 2843mm
    1920’s 2627mm
    1930’s 2614mm
    1940’s 2375mm
    1950’s 2372mm
    1960’s 2408mm
    1970’s 2480mm
    1980’s 2425mm
    1990’s 2705mm
    2000’s 2611mm
    2010’s 2756mm

    The 2010 decade has been estimated from 2010-2013 plus Dec.2013 and Jan.2014.
    Many reports have only gone back to the 1950’s in order to present an apparent rise over the past three decades

  7. Andy DC permalink
    February 17, 2014 9:15 pm

    Nothing indicating drastic climate change in those charts. Considering the wide swings in climate over the past, it seems like our recent climate has been remarkably stable.

  8. J Asquith permalink
    February 18, 2014 12:37 am

    Looking at the slightly lower winter totals pre-1850, and the slight dip mid 20th century makes me want to hazard a guess that in colder periods more precipitation falls as snow, thus depressing total precipitation figures.

  9. Neil Hampshire permalink
    February 18, 2014 7:12 pm

    Just checked rainfall for England Dec./January back to 1910

    !914/15 276mm
    1929/30 280mm wettest
    1959/60 266mm
    1994/95 261mm
    2013/14 274mm

    Again you can’t call it unprecedented

    • February 18, 2014 8:18 pm

      Is that the E&W series, Neil, or the Met “England ” set?

      Paul

  10. Neil Hampshire permalink
    February 19, 2014 5:10 am

    Paul,
    I used the Met England set because January (158.2mm) keeps being quoted as the highest ever January on record. I thought this data was most relevant to the current floods in Somerset and The Thames.

  11. Neil Hampshire permalink
    February 19, 2014 5:26 am

    Just double checking my figures

    2013/14 Dec 116.7 + Jan 158.2 = 274.9 (274 rounded)
    1929/30 Dec 165.5 + Jan 115.1 = 280.6 (280 rounded)
    1914/15 Dec 179 + Jan 97.1 = 276.1 (276 rounded)

    My Excel spread sheet appears to be rounding to the next lowest integer.
    I should perhaps have quoted to the first decimal place

  12. DaveS permalink
    February 20, 2014 11:58 pm

    According to a piece in the Telegraph the MO are now claiming this has been the wettest winter on record, 19.2 inches, beating the previous wettest, 1995 (19.1 inches) – the measure seems to be from December 1 to this Wednesday. Does that tally with the available data?

  13. Ulric Lyons permalink
    February 21, 2014 2:26 am

    What you need to look at is summer and winter rainfall. It takes cooler than normal temperatures in summers to increase rainfall, but warmer than normal temperatures in winters to increase rainfall. While around the equinoxes the response is poorly defined. So with cooling what we should see as a trend, is wetter summers and drier winters:

  14. Brian H permalink
    February 25, 2014 3:29 am

    Does “reversed” not imply a switch of some precip from summer to winter, balancing out in the main?

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