NCA4: Eastern U.S. Fact Sheet

Eastern United States: A Prime Example Of Growing Flood Risk from Climate Change

As the atmosphere warms, its ability to hold moisture grows. This leads to heavier downpours and more flooding. This has already been shown across the Eastern US, with the northeast already experiencing an observed increase in how frequent and intense heavy rain events have grown.

Because of climate change, sea levels have already risen about a foot, leading to more frequent and extensive high tide/sunny day/nuisance flooding.

Hurricane activity has increased in recent decades due to climate change, and especially when combined with the higher sea levels and warmer air and water temperatures, they have already and will continue to grow more damaging.

While rising temperatures and other impacts certainly won’t spare the East Coast, flooding from extreme downpours, hurricanes and high tides have already begun demonstrating the danger of climate change. If significant measures are not taken to reduce emissions, the economic impacts of climate change will be hundreds of billions of dollars.

The National Climate Assessment, Volume 2 features a variety of information on climate change impacts across the Eastern United States. Here are some highlights.

Climate Change is Already Flooding the East Coast through Sea Level Rise, Hurricanes and Storms:

  • High tide flooding now poses daily risk to businesses, neighborhoods, infrastructure, transportation, and ecosystems in the Southeast. It has doubled or tripled in some places, and increased by a factor of 10 or more over the last 50 years for many cities in the Northeast.
  • Since 1901, the Northeast has seen some of the biggest increases in the frequency and intensity of heavy precipitation, and this is expected to continue.
  • Atlantic hurricane activity has increased since 1970 because of more greenhouse gasses and less aerosol emissions.
  • Along the northern U.S. Atlantic coast, sea level rise rates were three to four times higher than the global average rate between 1950 and 2009.
  • Sea level rise is causing Louisiana to face some of the highest land loss rates in the world, forcing the  Isle de Jean Charles Band of the Biloxi-Chitimacha-Choctaw Tribe to resettle. Between 1985-2010, the rate of wetland loss was 16.57 square miles per year, the equivalent to losing the size of one football field as quickly as every half hour, or as slow as every 90 minutes.
  • The growing numbers of extreme rainfall events is stressing the aging infrastructure in the Southeast. Charleston, SC estimates that each crosstown flood costs $12.4 million, and is projected to face 180 days of tidal flooding a year by 2045.
  • The east coast has over 7,000 miles of road already threatened by high tide flooding.

Warming is Already Here, Causing Health Problems That Will Grow with Future Emissions:

  • The range of suitable habitats for other mosquito vectors such as the northern house mosquito (which transmits West Nile Virus) and the Asian tiger mosquito (which can also transmit West Nile Virus and other diseases) are already spreading in the south, and are expected to continue shifting northward into New England as a result of climate change.
  • Between 2015 and 2016, Rhode Island has seen three more weeks of uncomfortably hot weather than it did in the mid-19th century. Some of the largest increases in heat-related mortality are projected to occur in the Northeast, with an additional 50–100 heat-related deaths per year per million people by 2050, and 120–180 additional deaths per million people by 2100 under the mid-high scenario.
  • The number of days with high minimum temperatures (nighttime temperatures that stay above 75ºF) has been increasing across the Southeast. Exposure to high nighttime minimum temperatures may reduce people’s ability to recover from high daytime temperatures, resulting in heat-related illness and death, particularly in the southeast.
  • Ocean and coastal temperatures along the Northeast Shelf have warmed three times faster than the global average. Because of warming waters, Vibrio a bacteria that causes food poisoning, have expanded northward and is responsible for increasing cases of illness in oyster consumers in the Northeast.

Climate Change is Ushering In an Era of Extreme Events:

  • Across the Southeast since 2014, there have been numerous examples of intense rainfall events—many approaching levels that would only be expected to occur once every 500 years. Of these events, four major inland flood events have occurred in just three years (2014–2016) in the Southeast, causing billions of dollars in damages and over a hundred deaths.
  • In August 2016, half of southern Louisiana received at least 12–14 inches of rainfall, flooding 50,000 homes across the region. Baton Rouge and Lafayette were hit the hardest, receiving upwards of 30 inches in a few days, and coastal locations got up to 20 inches.
  • 2015 was a record year for coastal flooding in several southern cities. Wilmington NC  experienced 90 days of flooding, Charleston SC 38 days, Miami FL 18 days, and Key West Florida experienced two weeks of flooding. Regardless of future emissions, by 2050 many southern cities could experience a month, 30 days, of high tide flooding.
  • In 2012, sea surface temperatures on the Northeast Shelf in the Atlantic rose approximately 3.6°F above the 1982–2011 average. This heat wave altered seasonal cycles and the early spring warming triggered an early start of the fishing season, creating a glut of lobster that lead to a severe price collapse. Although an outlier, the temperature in 2012 was well within the range projected in the region by the end of the century under the higher scenario.

If We Don’t Reduce Emissions, We Can Expect More Climate Damages:

  • The trend of rainfall increases is expect to continue across the northeast and eastern U.S.
  • The strongest hurricanes in the Northeast are anticipated to become both more frequent and more intense in the future, with greater amounts of precipitation.
  • Sea level rise in the Northeast is predicted to be greater than the global average. Even the lowest probability scenarios where greenhouse gas emissions are abated within the short term projected sea levels rising upwards of 11 feet on average.
  • Without significant adaptation measures, many Southeast coastal cities will experience daily high tide flooding by the end of the century.
  • On the East Coast, over 7,500 miles of roadway are in high tide flooding zones.

  • Thirty-two percent of open-coast North and Mid-Atlantic beaches are predicted to overwash during an intense future nor’easter type storm, a number that increases to more than 80% during a Category 4 hurricane.

The Economic Impacts of Climate Change Will Be Significant:

  • By 2100, sea level rise will likely increase property losses from hurricanes by $11 billion to $17 billion dollars.  
  • The Southeast is expected to lose over a half-billion labor hours by 2100 due to extreme heat, a cost of $47 billion.
  • High emissions scenario where climate change continues unchecked points to a potential loss of $230 million for the shellfish industry.
  • Estimates of coastal property losses and protective investments through 2100 due to sea level rise and storm surge vary from less than $15 billion for southeastern Massachusetts to in excess of $30 billion for coastal New Jersey and Delaware.
  • The combined impacts of sea level rise and storm surge in the Southeast could reach $99 billion a year under a higher emission scenario. Even in the low emission scenario, damages of $79 billion are projected by 2090.
  • Climate change is expected to increase the current $73 billion in temperature-induced railway delay costs by $25–$60 billion, with some of the greatest impacts in the Northeast.
  • The Northeast winter recreation economy generates $7.6 billion annually, and rising temperatures have decreased the average length of the winter recreation season. Decreasing amounts of the natural snow and ice cover that are critical to snowmobiling, snowshoeing, cross-country skiing, and ice fishing may make these activities not economically viable by 2090.
  • Workers in the agriculture, forestry, hunting, and fishing sectors together with construction and support, waste, and remediation services work are the most highly vulnerable to heat-related deaths, representing almost 68% of heat-related deaths nationally, and six of the ten states with the highest occupational heat-related deaths in these sectors are in the Southeast.
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