The Sands Of Time

Judging by the reporting on the BBC website, the Welsh coastline is at serious risk of worsening flooding and erosion, caused by climate change, of course.

On 20th September 2019 we were asked, pointedly, “What is climate change doing to Wales?”.i Inevitably, the answer wasn’t pretty:

Alun Williams, cabinet member for carbon management in Ceredigion, said rising sea levels were threatening its flood defences.

The local authority is trying to plan how to manage the effects of climate change along the coast.

Stood on the shingle ridge which acts as a barrier between land and sea at Tanybwlch beach near Aberystwyth, Mr Williams said: “The sea is overtopping this bank much more regularly than it used to – it’s just a matter of time before it breaks through and moves inland.”

Rising sea levels and more frequent storms mean there are fears this defence could soon be breached.

16th July 2021 saw a stark warning:

Climate change: ‘Sleepwalking into oblivion’ coastal erosion warning.ii

0n 28th September 2021 we were toldiii that:

Latest projections show 11.3% of land in Wales will be at risk from flooding from rivers or the sea – a rise from the 9.86% previously predicted.

Minister Julie James said the new advice will help protect communities from the effects of climate change.

“Flood risk and coastal erosion in Wales is increasing as a result of climate change,” she said.

Appropriately, Halloween 2021 saw another scary story, wrapped up in a bigger articleiv about climate change and Wales, its response to it and its threats. Worryingly:

Just under 12,000 properties are at high risk from coastal or river flooding. There are just under 10,000 at high or medium risk of tidal flooding alone.

This could increase by 260% by the 2080s – while 2,126 properties are likely to be at risk of coastal erosion where defences are not maintained.

Less than a fortnight later, on 12th November 2021 we were told that because of “Climate change: Size of Wales may change due to coastal erosion”.v

Clearly there doesn’t need to be any significant new development before a scare story can be repeated (ad nauseam, since this was the time when BBC climate correspondents were breathless with excitement about COP26).

History

And so it came as a bit of a surprise when, on holiday in Snowdonia last month, we visited Harlech Castle, and were confronted by a sign which said:

Today the sea is a long way off, but in 1283 it lapped at the foot of the rock. This meant that Harlech Castle could be supplied from the sea during a siege.

…Where did the sea go? Huge storms in the 14th century led to the build-up of sea dunes, pushing the sea back and creating marshland. The river estuary provided tidal access to the castle until the 17th century. Over time the marshland was reclaimed for farmland; the estuary was lost, and Harlech became landlocked.

Certainly, looking out from the castle, the sea was a good distance away – perhaps as much as half a mile off.

Soon afterwards, we visited Anglesey and took a look at Beaumaris Castle. The situation here isn’t quite so dramatic, but the sea is again some distance away from the castle, at least 200 yards, I would guess. It wasn’t always that way, however. “The gate next-the-sea entrance protected the tidal dock which allowed supply ships to sail right up to the castle.”vi

These mediaeval castles, which were once next to the sea, and are now some distance from it, set me thinking, and then I remembered Caerlaverock Castle, this time in southern Scotland (on the Solway Firth). We visited it a few years ago, and I seemed to remember something similar. A quick internet search confirmed that my recollection was not mistaken:

When built it stood at the head of a tidal inlet at a time when the sea level was higher than it is today.vii

What? Sea levels higher than today? How can this be? Didn’t the hockey stick demonstrate that tales of a Mediaeval Warm Period being warmer than today were nonsense? Aren’t sea-levels inevitably linked to CO2 emissions?

Historical information can be so inconvenient, and so can modern researchviii:

It is now also believed that changes to the coastline caused by “extreme weather events” may have helped push the Maxwells from their home.

Stefan Sagrott, Senior Cultural Resources Advisor at Historic Environment Scotland said: “Working with the University of Stirling, we are undertaking palaeoenvironmental coring and analysis at Caerlaverock Castle to better understand the events which led to the abandonment of the ‘old’ castle in favour of the ‘new’ one.”

The harbour survey will date it for the first time with [sic] it hoped waterlogged artefacts of leather and wood could help tell the story of everyday life at 13th Century Caerlaverock.

Mr Sagrott said: “It is thought that extreme weather events caused gravel ridges to be driven from the sea to the coast, which affected the castles [sic] relationship with the coast, potentially changed the water table and possibly sealed off the harbour as well.

Tidal Gauges

There is a big push to persuade us that climate change is causing stormier weather. The fact that the UK has experienced severe storms throughout its history might go some way towards suggesting that these claims are exaggerated or even plain wrong. However, even if that is the case, rapidly rising sea levels would undoubtedly be a real problem. Anyone with a building on or near the sea might well be in trouble if sea levels rise.

However, this was always the case. Whether due to greenhouse gas emissions and/or other anthropogenic factors, temperatures have been rising globally since the end of the Little Ice Age. Inevitably this must lead to ice melt, and insofar as the melting ice is not sea ice, that must lead to rising sea levels. So the problem of coastal erosion and rising sea levels is not new. It only becomes an issue, which can fairly be attributed to climate change, if the rate of sea level rise is accelerating.

Fortunately there are some fairly comprehensive records available on-line which we can study with a view to ascertaining what trends there might be with regard to sea level rise. The National Tidal and Sea Level Facility websiteix contains data for 49 locations around the UK coast, from Aberdeen to Workington, from Belfast to Whitby.

I have spent some time eye-balling these charts, and I cannot discern an accelerating trend in any of them. Admittedly, it may in some cases be that the land is rising (isostatic rebound following the last ice age seems to be generally accepted as a real phenomenon), and this might distort the extent to which sea level rise appears to be a problem, though I can’t see that it would distort the gauge readings.

In any event, the readings from the Welsh tidal gauges don’t seem to justify the hysteria on the BBC website. Perhaps I would feel differently if I lived very close to the coast.

Conclusion

The question of sea level rise relative to land is complex. As Wikipedia puts itx:

As well as the addition of melted ice water from glaciers and ice sheets, recent sea level changes are affected by the thermal expansion of sea water due to global warming, sea level change due to deglaciation of the last glacial maximum (postglacial sea level change), deformation of the land and ocean floor and other factors. Thus, to understand global warming from sea level change, one must be able to separate all these factors, especially postglacial rebound, since it is one of the leading factors.

In short, hysterical claims about climate change, rising sea levels and erosion, do little justice to a complex subject, and ignore an awful lot of inconvenient history.

Endnotes

i https://www.bbc.co.uk/news/uk-wales-49753740

ii https://www.bbc.co.uk/news/uk-wales-57852719

iii https://www.bbc.co.uk/news/uk-wales-58711041

iv https://www.bbc.co.uk/news/uk-wales-58706283

v https://www.bbc.co.uk/news/uk-wales-59223819

vi http://www.beaumaris.com/index.html

vii https://www.transceltic.com/scotland/caerlaverock-castle

viii https://www.scotsman.com/heritage-and-retro/heritage/story-of-scottish-castle-that-vanished-750-years-ago-to-be-unearthed-3301811

ix https://ntslf.org/products/sea-level-trend-charts

x https://en.wikipedia.org/wiki/Post-glacial_rebound

via Climate Scepticism

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April 19, 2022 at 03:58PM

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