A recent study on changes in sea level since 800 BC shows that sea level is now rising at a rate that is higher than any other period in the last roughly 3000 years. The study was based on a new dataset of sea level elevations at 24 locations around the globe. You can read more about the study and its implications for coastlines at the Washington Post here. One of the authors of the original study gives a somewhat more technical description in his blog here.
