My 'reality-based decision making' post prompted a comment asking for my thoughts about sea level rise, which is more than sufficient excuse to turn to that. An additional excuse is that it provides a chance to look at how to decide climate time scales for something other than temperatures. For global mean temperature trends, I found that you need 20-30 years to determine a climate trend. We'll see that it is 40-60 years, 60 for preference, for sea level.
My starting point for data was the University of Colorado sea level group. They provide satellite data back to late 1992. High quality data, but only for a short period of time. If global sea level's time scales are like global mean temperature's, then it's only just gotten long enough to provide a climate number. Fortunately they list links to other sea level groups, including the Permanent Service for Mean Sea Level. They have three global reconstructions available. I'll take this one -- published in the scientific literature as: Recent global sea level acceleration started over 200 years ago?", Jevrejeva, S., J. C. Moore, A. Grinsted, and P. L. Woodworth (2008), Geophys. Res. Lett., 35, L08715, doi:10.1029/2008GL033611 -- on the grounds that it covers the longest time period and has the most recent literature publication date. It will be a good project for a reader to see if the conclusions here change, and how, if you use one of the others instead.
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