[gondramB]

" It has been estimated that another 25 years of data collection will be required to make a distinction between these factors."

Who estimated that?

[kidd]

I cannot find my exact source, but the following well-sourced article:

http://www.agu.org/revgeophys/dougla01/node3.html

provides a good discussion of the difficulties in determining sea level, and that many more years of data collection are required to determine the rate of sea level change.