Over the past two decades, climate change has triggered an increase in the risk of flooding of coastal areas by one and half times. According to the findings of an international team of scientists published in the journal Nature Communications, this increase is caused mainly by rising sea levels and the strength of storm surges. In the future, the duration of the sea’s exit beyond the coastal strip, including in the Far East, will increase by several tens of times. A summary of the study is reported in a press release on Phys.org.
The researchers used an ALOS World 3D digital surface model with a resolution of 30 meters (AW3D30). AW3D30 was obtained between 2006 and 2011 using optical stereo photogrammetry when two satellite images of the surface taken from different positions are compared. The analysis was limited to the model’s coverage of the surface from 60 degrees north latitude to 60 degrees south latitude. The scientists also used additional databases to determine two key parameters of coastal topography: the slope of the beach and the maximum land (subaerial) height of the coast.
Scientists also used data on sea level anomalies near the coast, wave height, and atmospheric conditions published by various services for monitoring the Earth’s climate. This made it possible to assess the extent to which the number of coastal overflows increased between 1993 and 2015 along the global coastline and to predict the future situation.
It turned out that the probability of overflow is highest in the Gulf of Mexico, the Southern Mediterranean, West Africa, Madagascar, and the Baltic Sea. Over the past two decades, the risk of the sea going beyond the coastline has increased by 50 percent. As for the future situation, the number of hours during which the coast is flooded with seawater will increase by 50 times during the XXI century in the worst-case scenario of global warming caused by high levels of anthropogenic emissions.
The number of overflow hours increases exponentially, i.e. at a faster rate than the average rate of sea-level rise. According to scientists, this will be noticeable by 2050, regardless of how seriously the Earth’s climate will change. By the end of the century, the acceleration will depend on the future scenario of greenhouse gas emissions and, consequently, on sea-level rise. Global warming will make events such as Hurricane Katrina in 2005, Cyclone Xynthia in 2010, and Typhoon Haiyan in 2013 more frequent and severe. As predicted by the authors of the study, the most seriously affected countries are in tropical areas, the northwest of the United States, Scandinavia, and the Far East of Russia.