News last week from my football club, to coincide with ‘Show Your Stripes’ Day, that it was launching a ‘progressive partnership’ with the University of Reading to improve its sustainability practices was welcome. What I didn’t know was that my hometown – in addition to giving football the greatest team the world has ever seen (well, the greatest team the Championship has ever seen, indisputably) – has also given the world climate stripes: the barcode-style heat map which demonstrates an easy-to-read visualisation of how the world, or your part of it, is getting hotter is an initiative of the University of Reading’s Ed Hawkins, a Professor in its well-established Meteorology Department. I was aware of climate stripes, of course, and there is a website which makes it relatively easy to show your stripes, but the hometown connection motivated me to dig a little bit deeper and see what I could do to show my own, very local, stripes (Ed – hoops, surely?)
The weather station for the Met Office – until 2003 also headquartered in the Royal(s) County – which is most local to me is South Uist Range. Located about 3km as the corncrake flies across open ground to the south-east of Ardivachar, what weather the Range station records is pretty much what we get. This station has, however, only been in use since July 1996, so its data – while building a dataset which will be comprehensive in the future – is of limited use in modelling the climate stripes for where I stay.
The other Met Office station for the Western Isles is Stornoway with a location which – at least in current terms – is adjacent to the airport. While the Met Office currently calls this location ‘Stornoway Airport’, I’ve no reason to assume it’s ever been located anywhere else than here at this point. Such a location is not untypical of many stations globally – they tend to be located on flat, open ground – and has led many climate change denialists to assume that recordings of termperature rises are associated with rapidly increased numbers of aircraft movements – that such locations thus give rise to false readings. We can, for evident reasons, probably discount such a theory at Stornoway Airport, though.
The station at Stornoway is one of the five oldest in use in the UK, dating back to 1873 and, indeed, the other four read as something like a tribute to the diversity of the UK, being Armagh and Oxford (both 1853), Southampton (1855) and Durham (1880). How such a spread came to be is rather heart-warming in its inclusiveness of the nations and regions of the UK. A graphic showing the climate stripes for these is readily available, with Sheffield substituting for Southampton, but the historic data for each of the Met Office’s ‘historic stations’ (37 in all) is easily found, so I thought I’d come up with my own, singular, version for Stornoway. Here, in a style which observes Hawkins’s commitment to ‘No words. No numbers. No graphs’, it is:
By way of explanation, the chart shows the mean annual temperature for Stornoway, from 1874 at the left-hand edge to 2021 at the right. Each column on the chart compares the mean temperature for that year with the mean for the twentieth century as a whole (1900-1999): annual temperatures significantly cooler than the C20 mean are shown in dark blue; those significantly warmer in dark red (with other shades indicating annual temperatures which are either cooler or warmer but with lesser significance). The annual means are an arithmetical average of the means for each month, themselves composed of the mean daily maximum temperatures in that month. There are other ways to approach the data – the station also records mean minimum temperatures and it would be possible to construct a figure for monthly mean temperature that way ((max+min)/2) but the outcome is, broadly, the same: Stornoway is clearly getting hotter.
We can see this from the red to the right of the chart; and we can also see it from the progression from the darker blues substantially to the left (the early part of the period), bearing in mind that we are comparing each annual mean to the mean for the C20 as a whole. Thus, the early years at the left (from 1874-1899) are largely cooler than the C20 mean while the later years to the right (2000-2021) are substantially warmer. Indeed, the mean maximum temperature for C20 is 11 degrees Centigrade; for the 26 years of the C19, the mean was 10.6 degrees; while for the 21 years of C21, the mean was 11.6. So, Stornoway has got hotter in the last 150 years by around 1 degree Centigrade – that’s pretty much in line with the average experience globally.
Obviously, annual temperatures fluctuate (as the following charts indicate, the year-to-year changes are volatile, which is why it is the trend that is most important, not what is happening in individual years (this cool summer included!). The pinker colours more or less in the centre of the climate stripes chart were in the later years of the Second World War and in the immediate period subsequently. We have indeed had temperatures that are ‘warmer’ in the past, too, but the years of the twenty-first century have been hotter for what is, in the context of this chart, an unprecedentedly sustained period. We might also record that the weather plunged into the cold in 1979.
I also had a look at the average ‘winter’ temperatures and the average ‘summer’ temperatures on the same basis (‘winter’ being defined as, within each calendar year, the six months from January-March and October-December inclusive while ‘summer’ is April-September inclusive. There are, of course, other ways to approach the data). While both summer and winter temperatures are rising, according to the annual means of the mean monthly maximum temperatures at Stornoway, it is the winter temperatures that are rising more quickly: the summers are getting comparatively warmer, but by less than the degree to which winters are becoming comparatively milder. The following charts compare the deviation for each season in each year from the C20 mean for that season (in Stornoway, 13.7C in ‘summer’; and 8.3C in ‘winter’); trendline added by Excel to demonstrate the comparative difference):
I suspected as much – rising annual rainfall (a measure of climate change also recorded by the Met Office stations), much of which falls in the winter months, speaks to rising winter temperatures. While there are still outliers – the 2010 winter was cooler than the C20 winter average by 0.76 degrees Centigrade – winter snows are, it seems, increasingly less and less likely; and, while the Caribbean may occasionally visit the Hebrides, this is going to be more evident from the photos than the reality for some time. Nevertheless, we are getting warmer.
As always, the essential question regards what is to be done. From an archaeological point of view, rising rainfall presents a particular problem both as regards ongoing digs and as regards the protection of particular established sites of interest. Temperatures becoming warmer also speaks to rises in sea levels which threatens coastal communities and sites of interest. There is only a limited range of effective measures which can be taken within such a field, however. The wider challenge to us all remains how we, as nations, address the rising temperatures that we all face. There are plenty of measures which can be taken about which much is already known, at societal level through decarbonisation, investment in renewable energy and building greater resilience in which biodiversity will flourish; through to individual decisions around transport and diet. Inevitably, there is a wide range of seriousness, a range of comparative priorities and plenty of lip service involved from those at governmental level charged with making policy which reflects these issues.
I’ll let this post bed in for a few days and then I’ll be changing the header picture to show my stripes, as above. It may not actually do anything in itself, but keeping the fundamental importance of the issue in mind, by quite literally nailing my colours to the mast, can never be a bad thing.