Coastal infrastructureSea level rise has been more rapid than previously understood: Study
The acceleration of global sea level change from the end of the twentieth century through the last two decades has been significantly swifter than scientists thought, according to a new Harvard study. The study shows that calculations of global sea-level rise from 1900 to 1990 had been overestimated by as much as 30 percent. The report, however, confirms estimates of sea-level change since 1990, suggesting that the rate of change is increasing more rapidly than previously understood.
The acceleration of global sea level change from the end of the twentieth century through the last two decades has been significantly swifter than scientists thought, according to a new Harvard study.
The study, co-authored by Carling Hay, a postdoctoral fellow in the Department of Earth and Planetary Sciences (EPS), and Eric Morrow, a recent Ph.D. graduate of EPS, shows that calculations of global sea-level rise from 1900 to 1990 had been overestimated by as much as 30 percent. The report, however, confirms estimates of sea-level change since 1990, suggesting that the rate of change is increasing more rapidly than previously understood.
The research is described in a 14 January paper in Nature.
“What this paper shows is that sea-level acceleration over the past century has been greater than had been estimated by others,” Morrow said. “It’s a larger problem than we initially thought.”
“Scientists now believe that most of the world’s ice sheets and mountain glaciers are melting in response to rising temperatures,” Hay added. “Melting ice sheets cause global mean sea level to rise. Understanding this contribution is critical in a warming world.”
A Harvard University release reports that previous estimates had placed sea-level rise at between 1.5 and 1.8 millimeters annually in the twentieth century. Hay and Morrow, however, suggest that from 1901 until 1990, the figure was closer to 1.2 millimeters per year. However, everyone agrees that global sea level has risen by about 3 millimeters annually since that time.
“Another concern with this is that many efforts to project sea-level change into the future use estimates of sea level over the time period from 1900 to 1990,” Morrow said. “If we’ve been overestimating the sea-level change during that period, it means that these models are not calibrated appropriately, and that calls into question the accuracy of projections out to the end of the 21st century.”
Hay and Morrow approached the challenge of estimating sea-level rise from a new perspective.
Typically, Hay said, estimates of sea-level rise are created by dividing the world’s oceans into subregions, and gathering records from tide gauges — essentially yardsticks used to measure ocean tides — from each area. Using records that contain the most complete data, researchers average them to create sea-level estimates for each region, then average those rates to create a global estimate.
