By H. Sterling Burnett -October 12, 2020
A letter to the editor in the Lewes, Delaware Cape Gazette, “Delaware in jeopardy due to climate change,” asserts human caused climate change is causing increased flooding in Delaware. This is wrong. Data demonstrate land subsidence, not accelerated sea level rise, is responsible for Delaware’s coastal woes.
In the article, Claire A. Simmer, a professor emeritus in the field of management, says climate change is causing the people of Sussex County (Delaware) “to have firsthand experiences with flooding due to global warming ….” Simmer’s claim is false.
Delaware has the lowest mean elevation above sea level in the United States. To the extent Delaware is losing slightly more land to the sea than many other states, Dan Leathers, Delaware’s state climatologist, reports it is not due to an accelerated rate of sea level rise or more intense storms. One must look for another cause to Delaware’s increased flooding, which Leathers provides: land subsidence.
Seas have been rising off the entire Atlantic coast, sometimes more rapidly and sometimes more slowly, since the end of the last ice age. Delaware has experienced approximately 13 inches of “sea level rise” over the past century. Only part of that rise is due to higher sea levels. Leathers says the rate of sea level rise is relatively steady at approximately four to eight inches over the century. Simultaneously, Delaware is experiencing approximately 1.7 millimeters of land subsidence each year, or nearly 7 inches over the century. So, land subsidence, due to the tectonic plate Delaware sits upon sinking, makes up at least half of the state’s sea level rise.
As explained in Climate at a Glance: Sea Level Rise, data from both the U.N. Intergovernmental Panel on Climate Change and NASA show sea levels have risen a global average of approximately 1.2 inches per decade since the middle of the 18th century. There has been only an approximate 0.3 inch acceleration in sea level rise in recent decades. Assuming all of the modest increase in sea level rise is due entirely too human-caused global warming, it is only a fraction of natural sea level rise.
Human civilization has successfully dealt with sea level rise across the centuries. It will be able to adapt to rising sea levels even more successfully in the coming decades by utilizing twenty-first century technologies.
Climate change is not making Delaware’s coastal flooding worse. City, county, and state governments of Delaware have long battled rising seas through a combination of beach replenishment, altering zoning ordinances to reduce damage from flooding, and hardening infrastructure. There is no reason for believing these same efforts won’t improve in the future, reducing the impacts of rising seas on Delaware’s growing coastal population.
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