By Paul Homewood
We are probably familiar with sea levels charts for Newlyn and North Shields, the main two long running tidal gauge sites in the UK;
Both show a steady rise around the long term trend, but with often large monthly variations. To get a better idea of long term trends, I have calculated decadal averages from the monthly data supplied by PSMSL.
North Shields only has full data up to 2017, so I have used 2008-17 as the current decade there:
We can see that sea levels actually fell in the middle of the last century, though curiously the drop occurred earlier in North Shields than Newlyn.
We can get a clearer picture though from the changes from decade to decade:
At Newlyn, there was a sharp rise in sea levels during the 1980s, but this presumably must be seen in context with the fall in the 1970s.
Similarly at North Shields, the fall in the 1960s and rise in the 1970s.
At both sites, sea level rise has actually slowed in the last decade. (The data available at North Shields, though not complete, shows a continued drop in sea level in 2018 and 2019).
And in both cases, the latest decadal rise is less than seen in some decades in the 20thC.
It is fair to add that the rise post 2000 is connected to the pause in sea level rise in the 1990s. The latter was of course the direct consequence of the Pinatubo explosion, which led to several years of global cooling.
This pattern of a slowdown or fall in sea levels in the 1960s and 70s is seen at many other sites around the world, as are rates of rise as high as now in the decades prior to that.
Both phenomena are, of course, consistent with warming in the Arctic in the 1920s and 30s, followed by the much colder interlude there, which ended in the 1990s. Global temperatures followed the same pattern too.
Although the overall rate of rise is around 2mm a year, because of periods when there was no rise at all there have been other periods when sea levels have been rising faster.
Annual sea level rise of around 3mm a year was typical prior to the cooldown, and is similar to what is being reported now by satellites.
Whether we enter another period of AMO related cooling in coming decades remains to be seen. But what the data conclusively shows is that, as far as the UK is concerned, the recent rate of sea level rise is not unprecedented, nor is there any evidence of it accelerating.
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September 3, 2020 at 03:48PM