Climate change is raising sea levels. Sea level rise has been tracked for quite a while and its risks to people who live in coastal areas have been the focus of a great deal of attention. But sea level rise is not a simple matter in that defining the baseline sea level is difficult to do.
It has long been known that sea levels vary considerably across the planet, and they have been rising more in some places than others. Much of the existing data has been based on global models that assume calm seas and ignore ocean currents and the effects of winds.
A new study by Dutch scientists has analyzed actual sea levels as measured by tidal gauges and has found that almost the entire scientific literature has dramatically underestimated current sea levels. While sea levels are not rising faster than previously thought, the baseline for future rise is considerably higher in most places.
The study looked at 385 locations and found that almost all of them had higher sea levels than previously thought. As a result, the number of people living in coastal areas at high risk is dramatically higher. For many low-lying coastal areas, scientific forecasts of how soon they may flood may be off by several decades. Making plans to protect coastlines is much more urgent than policymakers used to assume.
In addition, a separate study of the world’s river deltas has found that subsidence rates of many are much higher than previously thought, making the impact of rising tides much greater. Threats to coastal communities, especially in the global south, loom large as the seas continue to rise.
