The rising sea level will not come like a tsunami, or like a spring flood. Or like a tide.The rise will be very slow. It will take decades and decades to rise. A person can walk a thousand times faster than the rising sea level. And the same with temperature. One cam walk much faster than the average change in temp. On this planet, life controls and sets the environment. .And except for the last millions of years, this planet has had much higher CO2 levels. Produced from life. This planet has been starving for CO2.
By what standard or reference could possibly be used to measure the rise? We can't use gravity. It changes all the time. Especially with a mass redistribution(water) We can't use distance, because the surface moves in six directions. We don't posses a fixed point A satellite is always moving up and down. Radio signals do not travel at constant c, thru a media, like our ionospheres and atmosphere. Or water at different temps and pressures. And of course, what will the spinning earth do to the distribution of the added water?
We have plenty of time to observe and adapt to it. Man can not create a planetary environment. .But we can adapt and modify very well to it.. Just look at all the climate extremes we live in now. It's a full human temperature scale now, always has been. Life always fills every limit.