Rising sea levels caused by a warming climate threaten greater storm damage to New York City.
Researchers say that if we cause large sea-level rise, that dominates future risks, but if we could prevent sea-level rise and just have the storm surge to worry about, projections show little chance in coastal risk from today during most years.
While the storms that strike New York City might be bigger and stronger, researcher say there may be fewer of them as changing storm tracks increasingly steer the storms away from NYC and toward other regions northward.
Researchers also created a map with storm surge predictions under different carbon emissions scenarios, indicating which parts of New York City could suffer the most.
Street map of New York City showing maximum projected future storm surge. Natural water is in dark blue, 2100 levels are in medium blue and 2300 levels are in light blue. The projections are for a 500-year flood: one that has a 1 in 500 chances of occurring in any given year
Researchers at Pennsylvania State University who conducted the study say that coastal damage increases if the sea level is higher before a storm, and if the extra surge caused by the storm is higher.
To make their projections, the researchers looked at the history and future of both sea level and storm surge, from pre-industrial times through 2300, in models that had been run for the full period.
The researchers focused on results from simulations with rapid carbon dioxide release, often referred to as ‘business-as-usual’ simulations.
Future changes in sea level and storms would be smaller if actions were taken to slow climate change, such as the Paris Accord’s goal of limiting warming to 3.6 degrees Fahrenheit (2 degrees Celsius).
Sea level has been rising, and it’s expected to continue rising as warming causes ocean water to expand, and ice on land to melt and release water into the ocean.
In addition, rapid changes in behavior of parts of the Antarctic ice sheet might cause much greater rise than is often included in coastal planning.
To create their models, the researchers first calibrated them to simulate the rates of historic sea-level rise.
Then they ran simulations for the future, with and without results of a recent study that projects large future Antarctic ice sheet melt with business-as-usual increases in levels of greenhouse gases.
If this instability in the Antarctic takes place, the future risk to New York City is dominated by sea level rise.
The researchers then estimated what the flood height of potential 500-year flood would be by 2100 and 2300.
A 500-year flood is one that has a 1 in 500 chances of occurring in any given year.
By 2100, the estimated 500-year flood height would be 17 feet (5.2 meters), and by 2300 it would be about 50 feet (15 meters).
According to the researchers, reducing warming enough to preserve the Antarctic ice would greatly reduce risk to New York City.
If sea level rise remains small, then changes in storm surge are the most important concern for future coastal risk to New York City.
Following previous research, the models also show that warmer conditions allow for stronger storms – but the models also show that the warming causes storm tracks to shift offshore and northward, away from New York City.
A cameraman walks past a puddle in front of the New York Stock Exchange, which was closed in the aftermath of Hurricane Sandy in New York October 30, 2012. Reducing warming enough to preserve the Antarctic ice would greatly reduce storm surge risk to New York City
‘If a shift occurs toward less common but possibly larger storms, it poses special challenges for coastal planners, and highlights the value of additional progress in understanding and projecting the tracks as well as the strength of these storms,’ says Michael E. Mann, director of Penn State’s Earth System Science Center and a co-author of the research.
‘Sea level is rising and higher sea level increases the damages from coastal storms,’ said Richard B. Alley, a Professor at Penn State and study co-author.
‘Human decisions about energy will be important in determining how much the sea rises and thus how much damage we face, and accurate projections of storms will help in minimizing the risks.’
Local residents use a small boat to wade through a flooded street in Breezy Point, Queens, New York City, New York, USA, 30 October 2012. Floods, fires and high winds caused by Hurricane Sandy killed at least 16 people and leaft 6.5 million without electricity