Forecasts of sea-level rise often remain abstract and difficult to grasp, as they usually give global average values for the year 2100. To get closer to the realities of human life, several US agencies have now calculated how much the oceans will rise along the US coasts by mid-century and how this will affect states, cities and communities – yes even for individual properties.
According to this, the sea level is likely to rise by an average of 25 to 30 centimeters between 2020 and 2050 – as much as in the past 100 years. “This is a global wake-up call and gives Americans the information they need to act now and prepare for the future,” said oceanographer Rick Spinrad of NOAA, which works with the space agency Nasa and the… US Geological Survey den 111-page report created.
Higher sea levels make coastal regions more vulnerable to hurricanes and smaller storms. By the year 2050, a “moderate” flood should occur on average ten times as often as today – i.e. four times a year on average. This means that some houses have to be evacuated and larger streets have to be closed. And “big” floods that can isolate entire cities should then occur five times as often as they do today, i.e. once every five years on average.
Even today, New Orleans can only be maintained with expensive pumps and dykes
Sea level rise will not be the same everywhere, as it depends locally on wind currents and the uplift and subsidence of the land. On the US west coast, it is smaller because stronger trade winds push the ocean water towards Asia. Therefore, an increase of “only” 23 centimeters can be expected for Seattle and 36 centimeters for Los Angeles, but for parts of the US east coast and the states of Louisiana, Texas and Florida on the Gulf of Mexico even up to 45 centimeters. Even today, New Orleans can only be maintained with expensive pumps and dykes. “Until now, we hadn’t imagined that we would have to give up entire metropolises because of climate change,” says oceanographer Martin Visbeck from the Geomar Helmholtz Center for Ocean Research in Kiel. “But that is already foreseeable now.”
the US report builds on sea-level rise projections from the current World Climate Report and regionalizes the data. “The study and those in it linked site bring the global figures to individual locations,” says Visbeck. “Anyone can go right up to their own house and see when their feet are getting wet.” This was only made possible by a better understanding of the causes of sea level rise and by the cooperation of the three US authorities.
Another finding of the report: By the year 2050, the rise in sea level can hardly be slowed down – no matter how much CO₂ the world has saved by then. Ambitious climate protection is only likely to pay off in the long term. On the other hand, sea-level rise by 2050 should only be a foretaste: The worst consequences of ice melt and the expansion of the seas as a result of global warming are only to be expected from the end of the century, especially if climate change is not limited. In this case, the US scientists even consider an average increase of more than two meters on the US coasts to be possible.