exchemist
Valued Senior Member
I do not have a definite answer, but this article: https://en.wikipedia.org/wiki/Sea_level_rise explains that sea level is measured by satellites in Earth orbit. It is not explicitly stated, but I presume the deviations in this orbit from circular are known and thus such a measurement fixes the height of the sea relative to the centre of the Earth. This, after all, is the one fixed point in the system we can rely on.https://www.topchinatravel.com/mount-everest/the-height-of-mount-everest.htm
Once again, understand that but I am not sure if that is a "standard". This link suggests Mt. Everest is rising at 4mm per year. I assume that is based on some sort of "standardization" of sea level. Yet it does not give an average (i.e. 4mm per/yr +/- 2mm). A mention of an average sea level is completely absent from the literature would you disagree?
On average yes, I can understand but what I am suggesting is this is not a standard. Yet this measurement is used for real world applications!
Sea level as a "standard of measurement" is useless as an average if we wish to know weather patterns for example.
I guess the point is going over your head. Could you please share when, as you say, this measurement has "changed all the time" in the scientific use of this particular measurement ?
Aviation, Cartography, Meteorology are just a few that require this measurement, averaged or not. Accuracy/prediction depends on this point in space.
According to my information the rate of rise of the Himalayas (relative to the centre of the Earth, I presume) is >1cm/yr and the mean rate of rise of the sea is ~3mm/yr.
But you are right. The articles I have seen on the web do not explicitly state what the rates of rise are measured relative to, so it is bit frustrating. Perhaps if a geologist reads this thread, he or she can confirm or explain further. Post 18 from Iceaura suggests it is not that simple.