Sea Level Rise And Storms In A Warming World: Growing Risks To Falmouth

Stories about the compelling scientific evidence of global climate change and regional and local impacts are reported almost daily. These articles in newspapers and popular magazines are based on a wealth of new studies published in scientific journals as well as two just-published climate assessment reports. The UN’s Intergovernmental Panel on Climate Change (IPCC) released its latest report (AR5) earlier this year and the US National Climate Assessment was released this spring. Both are dense reading for the lay public, but each has a summary of key findings and recommendations. The basic conclusions of both reports are that climate change is underway now with a variety of impacts, is likely to increase in the future, is largely due to the emissions of greenhouse gases into the atmosphere from the burning of fossil fuels and land-use practices over the past century and longer, and enough is known of the risks to take action now to address climate change. The evidence for global warming is unequivocal, accepted as reality by more than 95 percent of climate scientists in the US and world-wide.

Coastal regions such as Falmouth, Cape Cod and the islands are particularly vulnerable to impacts of a warming world such as sea level rise, greater storm activity, saltwater intrusion into fresh water aquifers, increased erosion, more frequent “nuisance” tidal flooding, loss of beach and wetland resources, and more extreme weather events. Adding to global sea level rise is the fact that the New England region is also undergoing land subsidence due to natural geologic processes of isostatic rebound related to loading of the crust during glaciation and unloading that started some 20,000 years ago when the glaciers covering this region started melting and retreating north. The Cape and islands are very much products of past sea level rise of about 400 feet and long-term coastal erosion of one to four feet per year. These dynamic processes are more active today and are very likely to increase in decades ahead. Sea level rise has already increased 50 percent in the past two decades and recent reports of accelerated ice sheet melting in Greenland and Antarctica suggest that sea level rise for Falmouth could be four feet or more by year 2100.

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Storms in the way of hurricanes and winter northeasters have also shaped the coast and caused damage and loss of life due to storm-surge flooding and high winds. The last significant hurricane was Bob in August 1991, which was minimal in strength but is still fresh in many memories for the damage it caused. Super storm Sandy in October 2012 was a much more powerful storm that impacted New Jersey and New York with high winds and a surge of about 14 feet and if not for a blocking jet stream, Sandy would likely have taken a more normal northeastern track up the coast and had more impact on the Cape and islands. It’s just a matter of time before the Cape is hit with a major hurricane such as Sandy. Hurricane Sandy was not caused by climate change but it was intensified by warm ocean waters, a warm atmosphere, and recent sea level rise along the New Jersey-New York coast.

Falmouth, as well as all coastal communities, needs to plan for climate change and implement cost-effective measures to adapt to what impacts are coming in the near future. The newly revised FEMA flood risk maps are a good guide to understanding vulnerability on a townwide and even individual property-specific lot basis, but its maps are actually conservative in conveying risk because the maps are based solely on historic storm and sea level rise data and model analysis. The maps do not factor in any climate change projections. Maps showing potential storm surge elevations for Category 1 through 4 storms are useful in visualizing the impacts of both surge and sea level rise of up to about 14 feet along the south coast and even higher surge along the Buzzards Bay coast. Much of Falmouth to Route 28 and Route 28A would likely be flooded and waves would add to the devastation of property.

Falmouth would be wise to act on the two reports done by the Coastal Resources Working Group over a decade ago, as well as reports by the state, the IPCC, and the National Climate Assessment that contain valuable information and recommendations.

(Mr. Williams is a coastal scientist, emeritus, with the United States Geological Survey.) 

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