Scientists overestimated the rate of sea level rise between 1901 and 1990, meaning Earth’s oceans have expanded more dramatically in the past 25 years and major coastal cities and island communities could be closer to going under than previous research has shown. That’s the crux of a new study from scientists at Harvard University published Wednesday in the journal Nature.
Based on their data, annual sea level rise from 1901 to 1990 was about 1.2 millimeters (.05 inches), roughly .3 to .6 millimeters less than the “standing wisdom” for that time period, said Robert Kopp, an associate professor of earth sciences at Rutgers University in New Brunswick, New Jersey, and a senior scientist on the study. “As you go back through the 20th century, the tide gauge record becomes sparser,” he said. “One of the things we’re interested in is global mean sea level – the volume of water in the ocean.” Previous research did not account for “gaps” in tide gauge data, according to Kopp. That was where the discrepancy between the Harvard data and previous data came from.