Considering the great number of regular variables in our ocean it's not acceptable to state the water was higher or not. To claim it is because of 'global warming' is a fine collection of bovine excrement.
Average water levels higher? Try the millions of tonnage of displacement on our oceans by shipping, cruise ships and the like. Maybe. localized Gravitational anomalies perhaps ( Hint: our '1G' is an average that varies, it's not absolute. )
There is so much about our earth we don't know. Trying to say an ocean is a few inches higher is laughable at best. You can measure the ocean anytime you want and only measure during your high tides or whatever. It's 'Confirmation Bias' at it's worst. We don't know how the Earth works well enough, and all this green crap could actually be making it worse.
The whole concept of carbon credits is tantamount to profiteering, scaremongering and a form of terrorism all it's own.
I only hope some day all the chicken littles that bought into this shceme will come to their senses and formal charges are brought against the perpetrators for crimes against humanity.