Reacción a "Sea level rise may be higher than previously thought, according to a study"

Sea level rise (SLR) is one of most serious and certain consequences of global heating. It is a field I have worked in for some two decades and I was genuinely surprised by the results of this study, which is not about reassessing how much SLR there might be in the future but about using the correct estimate of present-day sea level. This might seem obvious, but unless practitioners and others working in the field understand the nuances of the different types of reference surfaces used and how they relate to coastal sea level it is easy to miscalculate the offset between coastal elevation and the sea surface height in that location.

What the authors demonstrate is that in the majority of impact studies, that is exactly what has happened. The wrong assumptions are made about what present-day sea level is and it turns out that it has generally been underestimated in key sensitive coastal areas. This has important implications for impacts of future SLR in terms of the area and number of people potentially affected in low lying areas such as south east Asia and the Nile delta. It does not affect how much SLR might occur in the future.

The authors estimate that the offset between the true sea surface height and that used in impact studies is around 24-27 cm. To put that in context, that is more than the total SLR that has occurred since the beginning of the 20th century. They highlight an important limitation in most coastal impact studies but their conclusions about how this will affect estimates of future coastal inundation are less certain. First, they assume a higher accuracy for estimates in mean sea surface height at the coast than is actually the case. The best way to assess this is against tide gauge data, which are actually located at the land/ocean boundary. Second, the elevation of the land surface in the coastal zone has relatively large errors, which compounds the difficulty in determining the relative difference between the height of the land and sea at the coast.