Met Office Sea Level Forecast: No Resemblance To Reality

  • Date: 12/02/14
  • Paul Homewood, Not A Lot Of People Know That

We have eight tide gauge stations along the English Channel, with records back to 1990. None them come anywhere near even the bottom of the Met Office’s forecast range. Time for the Met Office to go back to the drawing board.

Mean sea-level trends from English Channel tide gauge records and their wider context

Taken from Haigh, I.D., Nicholls, R.J., Wells, N.C., 2009a. Mean sea-level trends from English Channel tide gauge records and their wider context. Continental Shelf Research, 29, 2083-2098

In the Met Office report, published this week, “The Recent Storms and Floods in the UK”, there is this statement: 

Sea level along the English Channel has already risen by about 12cm in the last 100 years. With the warming we are already committed to over the next few decades, a further 11-16cm of sea level rise is likely by 2030. This equates to 23-27cm (9-10½ inches) of total sea level rise since 1900. 

My Garden Pond & Tallbloke have already picked up on this, and got some clarification from the Met Office’s Richard Betts, who has made it clear that the projected rise is from 1990, and not now.

That would imply a rate of rise of between 270mm and 400mm per century, between 1990 and 2030.

So what have sea levels been doing so far since 1990? We have eight tide gauge stations along the English Channel, with records back to 1990. (Dover only has data to 2010, the others are all updated to 2012). The chart below shows how sea levels have changed, according to data from the PSMSL, (Permanent Service for Mean Sea Level). All figures are in mm.

 

1990 2012 Change/Decade
Dover (To 2010) 7073 7090 8.5
Portsmouth 7026 7068 19.1
Weymouth 6949 6965 7.3
Devonport 7073 7088 6.8
Newlyn 7079 7110 14.1
Le Havre 7048 7082 15.5
Cherbourg 7057 7086 13.2
Roscoff 6952 6993 18.6
Crude Average 12.9

http://www.psmsl.org/data/obtaining/

None of the stations come anywhere near even the bottom of the Met Office’s forecast range, and the, admittedly, crude average is bang in line with the 12cm rise over the last century.

residual1980.png

It is also important to take into account isostatic changes. Along the Channel, land is sinking by between about 0.5mm and 1.2mm a year. (On the English side at least!) In other words, at least a half of the observed sea level rise seems to be accounted for by this factor. Without this, we are looking at only a few inches a century.

 image

So where does all of this leave the Met Office’s forecast? According to them, there should be a sea level rise of between 82mm and 132mm in the next 18 years. In other words, 4.5mm to 7.3mm a year, which equates to a rate of 17 to 28 inches a century.

Full story