Background
Global climate models, in the words of the authors, "show an increase in the rate of global average sea level rise during the 20th century," which phenomenon has become the basis for all sorts of doom-and-gloom prognostications about the world's coastlines being inundated by advancing seas as mankind continues to burn ever more fossil fuels, which process emits ever more CO2 to the air and (theoretically) enhances the atmosphere's greenhouse effect.  But are these predictions supported by any real-world evidence?

What was done
Several prior studies have concluded that the rate of global sea level rise has been rather stable over the past century or more at a mean value of approximately 1.8 ± 0.3 mm yr^-1 (Douglas, 1991, 1992; Maul and Martin, 1993; Church et al., 2004; Holgate and Woodworth, 2004).  Nevertheless, White et al. (2005) conducted one more analysis of the available data in an attempt to find the elusive predicted increase in the sea level's rate of rise, comparing estimates of coastal and global averaged sea level for 1950 to 2000.

What was learned
When all was said and done, White et al. concluded that their results confirmed earlier findings of "no significant increase in the rate of sea level rise during this 51-year period," i.e., over the last half of the 20th century, including the last two decades that are typically demonized by climate alarmists for their supposedly "unprecedented" rate of temperature increase.

What it means
These findings suggest that if we cannot find any real-world evidence of an acceleration in either global or coastal sea level rise over the entire industrial period, when the air's CO2 content rose by about a third and we are told the planet experienced a warming that was unprecedented over the past one to two millennia, something is drastically wrong with the fodder the world's climate alarmists are feeding the popular press.

References
Church, J.A., White, N.J., Coleman, R., Lambeck, K. and Mitrovica, J.X.  2004.  Estimates of the regional distribution of sea level rise over the 1950 to 2000 period.  Journal of Climate 17: 2609-2625.

Douglas, B.C.  1991.  Global sea level rise.  Journal of Geophysical Research 96: 6981-6992.

Douglas, B.C.  1992.  Global sea level acceleration.  Journal of Geophysical Research 97: 12,699-12,706.

Holgate, S.J. and Woodworth, P.L.  2004.  Evidence for enhanced coastal sea level rise during the 1990s.  Geophysical Research Letters 31: 10.1029/2004GL019626.

Maul, G.A. and Martin, D.M.  1993.  Sea level rise at Key West, Florida, 1846-1992: America's longest instrument record?  Geophysical Research Letters 20: 1955-1958.