Um, you can measure sea level, and while some land is rising and sinking tectonically the vast majority is not, which is why the warmers cannot show one single landmark sinking despite all the claimed "ocean rise" that does not exist because the warmers have been lying all along about 90% of Earth ice on Antarctica, which is not "melting" (no liquid water present) and has been adding ice for 40 million years....
A new NASA study says that an increase in Antarctic snow accumulation that began 10,000 years ago is currently adding enough ice to the continent to outweigh the increased losses from its thinning glaciers.
www.nasa.gov