evidence: Considering the twentieth century as a whole, Munk (2002) described GMSLR as an "enigma": it began too early, it had too linear a trend, and it was too large. The first two problems relate to an expectation, based on a general understanding of the processes concerned, that in a warmer climate the rates of thermal expansion and of glacier mass loss will tend to increase. Therefore, we might suppose that these climate-related contributions to GMSLR increased during the twentieth century. However, the trend of GMSLR during recent decades was actually not very much larger than during the twentieth century as a whole. For instance, Church and White (2011) find 1.9 ± 0.4 mm yr−1 for 1961–2009 and 1.7 ± 0.2 mm yr−1 for 1900–2009. The third problem, of GMSLR being too large, is shown by the model-derived estimates of contributions reported by Church et al. (2001), which could explain only 50% of twentieth-century GMSLR; likewise, Moore et al. (2011) identify a substantial residual for 1850–1950. [...] Although we think that progress has been made toward accounting for twentieth-century GMSLR, it is evident that there are still substantial uncertainties in the contributions and in how they relate to global or regional climate change. A complete explanation remains to be achieved. This is an important goal, because it would put us in a better position to judge the reliability of models of the contributions, to attribute past GMSLR to climate forcings (anthropogenic or natural), and thus to increase our confidence in projecting future sea level rise.