Ignoring the Worst Case Scenario Comes with a Hefty Price Tag
by Sarah DeWeerdt
March 7, 2017 – By 2100, economic losses from climate change-related sea level rise and coastal flooding in European port cities could top US$1 trillion every year, according to researchers from the Basque Center for Climate Change.
Most previous studies on this topic have focused on predicting likely or average losses from sea level rise.  The new analysis focuses on the 5% worst-case scenarios, which have a low probability of actually coming to pass but a huge potential for damage if they do.
Climate-change economists are increasingly interested in these so-called “tail events.”  Simply because they would be so devastating, they argue, the possibility of such events must be accounted for.
The researchers used a dataset from a 2014 study to build a statistical model of the full range of possible sea level rise between 2007 and 2100, for 19 European coastal cities.  Then they ran a computer simulation to predict the economic damage from sea level rise and coastal flooding for each city.
The calculations are based on the assumption that carbon emissions will continue at current rates – another element of the worst-case scenario.
For all 19 cities together, annual average losses increase from US$1.2 billion in 2030 to US$40.8 billion in 2100.  In the worst-case scenario, the picture is even starker: overall damage could reach US$4.8 to US$8.2 billion dollars in 2030, and US$92.4 to US$114.8 billion annually in 2100, the researchers report in the journal Frontiers in Marine Science.
The most vulnerable European cities are Istanbul and Izmir, Turkey; Odessa, Ukraine; Rotterdam, the Netherlands; and St.  Petersburg, Russia.  These 5 cities top the list at all time points between now and 2100, regardless of the method used to estimate economic losses.  However, their specific ranking varies.
More broadly, the study suggests that coastal cities are hotspots of climate risk, but also centers of opportunity for climate adaptation.
Global population and infrastructure are concentrated along the world’s coastlines: 10% of the human population lives less than 10 meters above sea level, and 2/3 of the world’s megacities with populations of over 5 million are located in these low-lying coastal areas.
Coastal cities will have to decide how much risk from sea level rise they are willing to tolerate.  But in order to do so, they need better information about what the risks really are.  Studies like the current one could help city officials make more informed plans to manage and mitigate the effects of climate change, the researchers say.
Source: Abadie LM et al. “Climate Risk Assessment under Uncertainty: An Application to Main European Coastal Cities.” Frontiers in Marine Science.2016.
 www.anthropocenemagazine.org/2017/03/when-it-comes-to-sea-level-rise-city-planners-should-prepare-for-the-worst/