IIRC sea level has been going up 3mm a year broadly speaking ever since we started measuring it.
So in 80 years time that is around 240mm.
Not even the height of a sandbag,
And, over the period, easy enough to build defences against, provided we don't have to rely on renewable energy...
They are well below sea level anyway.
As is the channel tunnel.
Provided we still have electricity for pumps, it wont happen,
Erm. Excuse me. You are not reacting in the appropriate manner. You should be running around in circles screaming. Also, remember to use K instead of C as it is apparently an indicator of intellectual superiority.
And it's increasing at an increasing rate, apparently. Data:
But still catastrophic in many parts of the world.
Except it isn't. Except where the land is sinking at in increasing rate.
In fact according to those figures, it fell 5.5 mm between 2019 and 2020.
Not really, since most low lying bits of land are in fact increasing in size.
Due to various sorts of deposition
>
The ones under the Thames don't often flood now. Don't you think there might be an engineering solution?
The 125 metre rise in sea level at the end of the last ice age will have wiped out all of the Pacific coral atolls. So now, 13,000 years later, there aren't any?
:-)
Build coffer dams round some of the station entrances, some aren't much above the current river level.. Difficult with the new one for the Elizabeth line at Canary Wharf, though.
RJH snipped-for-privacy@gmx.com posted
But the (very slightly) steeper gradient of more recent years (from about 2006 to about 2010) is well within the range of variation exhibited over the whole period. For example, in 1929 the gradient quite suddenly became much steeper, until about 1961 when average sea level actually *fell*, and took a long time to recover to its previous value. The slightly steeper gradient of the early 2000s could easily be a similar blip.
And that's assuming that the data is accurate and has been measured in a consistent way over the whole period.
Are you sure you're reading it correctly - values are a 'change in sea level in millimeters compared to the 1993-2008 average'.
So levels to my untrained eye have been rising fairly consistently since the records started. Here's the text/graphics:
I think that's why they've used 2 measures - again, they look to be reasonably consistent between eachother.
It's because it keeps raining.
RJH snipped-for-privacy@gmx.com posted
As TNP said, the broad trend is upwards at about 3mm a year. But there have been many reverses, recoveries and accelerations on the way. The recent one looks exactly like several previous accelerations.
If you draw a straight line through the datapoints at April 1928 and April 2019 you will see an interesting thing. That line is pretty close to a best-fit trend line for the data until about April 1961. Then suddenly the sea level plummets rapidly by about 25mm, and remains well below that trend line for another fifty years. Only then does the sea level recover to the number that would have been predicted by the
1928-1961 trend line.What this means in geophysics terms, I have no idea. But in terms of mathematics, it shows that in 1928 the historical records did not predict actual sea levels with any accuracy for the next eighty years. The same is very probably true today.
Yes, agreed.
Algernon Goss-Custard snipped-for-privacy@nowhere.com posted
Sorry, I meant "in 1961".
Yes, that's the trend over the past 20 years or so. Overall, over the 140 year period, it's about 1.8mm.
Mmm. I've just plotted the data as best as I can. My 1928-2019 line shows some marked dips (1962, 1978, 1994), but peaks over the line (1950, 1992). By eye, yes, it does look like a fairly predictable rise over the period, that goes wrong around 2002, with a steep rise way above predicted. It does look to me like the post 2002 data is showing a significant acceleration in levels rising.
But even by my standards that's a pretty sloppy interpretation. I can't see how the statistical significance of the various dips and peaks can be estimated, or why they're relatively severe in the first 40 years.
I'll have to defer to your grasp of maths. It looks to me as though it would, with the deviation starting around 2002. But I'm way outside my comfort level :-)
What are the error bars on these data points?
Well this bit, taken from the link above, wasn't written by a scientist.
"Since the early 1990s, sea level has been measured from space using radar altimeters, which determine the height of the sea surface by measuring the return speed and intensity of a radar pulse directed at the ocean. The higher the sea level, the faster and stronger the return signal is."
The return signal travels at the speed of light, like all EM radiation. What the fathead probably means is that if the sealevel is higher, the signal will return sooner. Well, duh!
But that doesn't answer my question. ISTM that taking such measurements requires a number of things to be known with great accuracy, including (but probably not limited to) where the satellite is, what the air pressure is at the target point on the ocean, what ocean currents there are at that point, ...
A rough heuristic valid for almost any noisy dataset is that the highest and lowest excursions from the trend line span about 6 std deviations. By eye that looks to be about 10 on whatever their vertical scale is.
I fitted the quadratic and found that the residuals were interestingly asymmetric with an enhanced high tail out to +32 and nothing below -17. I only analysed 1900-2020 since MickeySoft Excel doesn't understand dates prior to that. These are the histogram of those residuals:
Bin Frequency Gaussian Fit
-17 1 2.129109766
-16 1 2.836116599
-15 1 3.712813028
-14 0 4.776777854
-13 1 6.039764124
-12 3 7.505124126
-11 5 9.16534355
-10 11 10.99999748
-9 21 12.97446296
-8 9 15.03969965
-7 21 17.13333491
-6 14 19.18216458
-5 22 21.10601728
-4 27 22.82274794
-3 21 24.25395381
-2 29 25.33087118
-1 26 25.99983995
0 19 26.22673274 1 23 25.99983995 2 26 25.33087118 3 24 24.25395381 4 25 22.82274794 5 12 21.10601728 6 16 19.18216458 7 17 17.13333491 8 23 15.03969965 9 13 12.97446296 10 14 10.99999748 11 13 9.16534355 12 12 7.505124126 13 11 6.039764124 14 8 4.776777854 15 3 3.712813028 16 5 2.836116599 17 3 2.129109766 18 1 1.570814821 19 0 1.138950623 20 1 0.811592024 21 1 0.56836014 22 0 0.391167192 23 0 0.264578287 24 0 0.175872908 25 0 0.114893817 26 0 0.073764489 27 0 0.046542637 28 0 0.02886075 29 0 0.01758803 30 0 0.010533671 31 0 0.006200051 32 1 0.003586442The local gradient averaged over 10k days has almost doubled since 1900.
+25 /10k days in 1900 +50 /10k days in 2000
It is the return trip time that determines the height. The echo
*strength* actually tells you how flat or otherwise the sea surface is.This intensity information is helpful for the survey since a reflection from a 10m swell is much less reliable as a measurement of ocean level one than from a flat calm sea with just a few small ripples on it. I expect they do use it to put error bars on the mean sea surface.
Averaged over the entire sea surface they can get remarkable high precision measurements from these radar survey satellites. Same technology is used to image near Earth asteroids using higher power ground based radar.
Sure, but my point is an article written by a press officer is unlikely to contain useful statistics. Also mildly amusing that the idea a few centimetres of sea level rise would give a usefully stronger signal 100 miles up. (As Martin says, signal strength does tell you something about the roughness).
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.