In the next 100 years continued sea-level rise will affect millions of people living in coastal areas. But projecting just how much those effects will be felt depends on which model you use.
The problem, a Florida State University researcher says, is that these projection models are inconsistent.
Assistant Professor of Sociology Matt Hauer has published a new study in Nature that lays out the issue by addressing a central challenge: the lack of a standard set of metrics for projecting exposure to sea-level rise.
One metric commonly used by researchers is the number of people at risk of sea-level rise. Hauer noted that current estimates of the number of people expected to be affected by sea-level rise globally this century range from 88 million to 1.4 billion, a range he calls “wild.”
“There are a lot of assessments in the literature for how many people could be at risk for sea-level rise, but the numbers are all over the place, to put it mildly,” Hauer said. “So the question was, ‘What do we do to make sense of all of these different estimates?’ We made an apples-to-apples estimate for the United States so we could look at those common metrics so we have direct, comparable estimates.”
Hauer said increasing the number and standardizing the metrics used in modeling will help with planning for sea-level rise. Other metrics frequently used are specified levels of sea-level rise, coastal floodplains and the low-elevation coastal zone.
“Oftentimes when scientists make these estimates they use just one or at most two metrics,” he said. “So if you make an estimate you could come up with one set of findings and then another person does it with a different metric and comes up with a totally different set of numbers.”
Hauer added that the use of one metric also produces results that are often narrowly focused and don’t account for other critical factors.
“When you use just one metric that only gives you part of the picture and you are going to miss parts of the risk profile,” he said.
The consequences of this approach are quite tangible, Hauer said, when considering public policies like adaptation planning and how resources are deployed for protective infrastructure.
The coasts are of particular concern both due to proximity to the sea and population growth in coastal areas, which is projected to increase 435% this century. Hauer said one of his big takeaways from the study is that even if coastal population didn’t grow, sea-level rise is going to affect more people as the sea encroaches further inland.
For more information, visit https://www.nature.com/articles/s41467-021-27260-1