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Sea levels are rising at faster clip as polar melt accelerates, new study shows

Thwaites Glacier in Western Antarctica. (AFP/NASA)

Global sea levels are climbing at a faster rate than previously thought, according to a new analysis that underscores scientists’ concerns about the impact of melting glaciers and ice sheets near the Earth’s poles.

The new research published Monday in the journal Nature Climate Change shows that the rate of sea-level rise appears to have accelerated over the past 15 years, a period in which scientists elsewhere documented a surprisingly rapidly retreat of some of Earth’s great ice masses, from Greenland to West Antarctica.

The findings appear to contradict earlier studies suggesting that the rate of sea-level rise had actually slowed slightly in recent years.

Australian scientists detected the increase in a study that analyzed decades of records from tidal gauges around the world, together with satellite data that show changes in water levels as well as subtle shifts in land formations.

Using these more precise measurements, the researchers discovered that scientists had slightly overstated sea-level rise that occurred in the 1990s, and underestimated the rate of increase since 1999, said Christopher Watson, a University of Tasmania geodesist who co-authored the study along with colleagues from the university and from Australia’s national science agency, the Commonwealth Scientific and Industrial Research Organization.

[A Harvard study also documented faster sea-level rise]

The adjusted figures showed ocean levels rising over the past two decades at a rate of between 2.6 and 2.9 millimeters a year — or just over a tenth of an inch, he said. That rate is consistent with the projections of the Intergovernmental Panel on Climate Change, the U.N.-sponsored scientific body regarded as the internationally accepted authority on global warming.

“The acceleration is also consistent with what we expect, given the increasing contributions from the West Antarctic and Greenland ice sheets,” Watson said in an e-mail.

Watson noted that sea levels can fluctuate naturally as water is exchanged between the sea and land, and for that reason, the higher rate of increase described in the study is too small to be regarded as statistically significant. What is clear, he said, is that sea levels are rising at roughly double the average rate observed in the last century, with significant implications for coastal cities around the globe.

The IPCC projects that, at current rates of warming, global sea levels could rise by as much as three feet by the end of the century.

“Accelerating sea level is a massive issue for the coastal zone — the once-in-a-lifetime inundation events will become far more frequent, and adaptation will need to occur,” Watson said. “Agencies need to fully consider the impact of accelerating sea level and plan accordingly.”

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