Is there A sea level?

E M Smith
"What we call “Sea Level” is the MEAN Sea Level. It is an average taken from a bunch of places around the planet and averaged. This “has issues”. ...... We’ve got 5 meter range fluctuations over 1000 years. So if the present ‘sea level’ rose by 5 meters, it would be back where it was in 1000 A.D.! So what SUV and coal fired power plants caused it to be so high back then? Eh? I have no idea if that bit of history is due to global shifts of ‘sea level’ or local geology shifts. Nor does anyone else. That there are similar dated ports and harbors in Turkey and Italy, now found well inland, implies to me that ‘sea level’ was higher, and has been dropping, and that any recent ‘rise’ is likely just due to a normal cycle of rise / fall on a 1000 to 2000 year basis. Pointing at present sea level changes as evidence of human induces warming is folly."