How much has the sea level risen in recent years?

Dear Tom,
Glaciers are melting and the melt water ends up in the oceans. How much has the sea level risen in recent years?


Mel Frazer,
Chicago

Dear Mel,
The oceans of the world have been rising at the rate of about one-eighth inch per year in the last few years, and the rate of rise has actually been increasing. Two factors are responsible for the rise: Land-based ice (glaciers and ice caps) is melting, and this probably accounts for about two-thirds of global sea-level rise. The remaining one-third of the increase is due to thermal expansion of ocean water; water expands as it is heated and the average temperature of the world ocean has been increasing. The global sea level in 2017 was 2.7 inches above the average in 1993. An additional rise of 12 to 30 inches is conservatively predicted by the end of this century, possibly much more.