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Climate Change

Southeast

Climate Impacts in the Southeast

Map of the Southeast including: Virginia, North Carolina, South Carolina, Georgia, Florida, Alabama, Tennessee, Kentucky, Arkansas, Mississippi, Louisiana, and eastern Texas.
Key Points
  • Coastal communities in the Southeast will likely face sea level rise, increased hurricane intensity, and storm surge, among other climate change impacts.
  • Higher temperatures, longer periods between rainfall events, and greater demand for water will likely strain water resources in the Southeast.
  • Incidences of extreme weather, increased temperatures, and flooding will likely impact human health.
  • Higher temperatures will likely affect the growth and productivity of crops and forests in the region.

Over 70 million people live in the Southeast. [1] The region includes many cities with populations over 250,000, including Houston, Jacksonville, Charlotte, Atlanta, Miami, and New Orleans. [1] The region's economy includes forestry, tourism, oil and gas production, and agriculture. The Southeast also includes 29,000 miles of coastline. [2]

The region's climate is generally warm and wet, with mild and humid winters. Since 1970, average annual temperatures in the region have increased by about 2°F. [3] Winters, in particular, are getting warmer. The average number of freezing days has declined by four to seven days per year since the mid-1970s. [3] Most areas, with the exception of southern Florida, are getting wetter. Autumn precipitation has increased by 30% since 1901. The number of heavy downpours has increased in many parts of the region. [3] Despite increases in fall precipitation, the area affected by moderate and severe drought, especially in the spring and summer, has increased since the mid-1970s. [3]

Average annual temperatures in the region are projected to increase by 4 to 9°F by 2080. [3] Hurricane-related rainfall is projected to continue to increase. Precipitation in southern Florida will likely decrease. It is unclear how precipitation will change in the rest of the region. Climate models are currently inconclusive as to whether the net change will be an increase or decrease. Models do suggest that rainfall will arrive in heavier downpours with increased dry periods between storms. These changes would increase the risk of both flooding and drought. [3] The coasts will likely experience stronger hurricanes and sea level rise. Storm surge could present problems for coastal communities and ecosystems. [3]

Image of hurricane overlaid by a map of the Gulf Coast and Eastern seaboard. Each hurricane strike that produced hurricane force winds over land from 1950 to 2010 is represented by a dot that is color coded by the appropriate Saffir-Simpson Hurricane Category, name, and year. The map shows that the majority of hurricanes hit the Gulf Coast and Southwest, with a handful that hit New York, Massachusetts, and Maine. Seven category four and three category five storms have struck the United States in that time span.

View enlarged image Source: NOAA (2010) (PDF)

Map of continental United States hurricane strikes from 1950 to 2010.

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Impacts on Coastal Resources

Densely populated coastal areas and coastal ecosystems in the Southeast are already experiencing relative sea level rise, hurricanes, and storm surge. Climate change is projected to exacerbate these existing threats.

Many coastal areas in the Texas and Louisiana are subsiding--local land elevation is sinking relative to sea level. Combined with global sea level rise, local subsidence will lead to a higher "relative" change in sea level at the local scale. Observed subsidence rates in the southeast are significant. For example, in Grand Isle, Louisiana and the plain of the Mississippi River delta, sea level is already rising at rates as high as 0.32 inches per year. [4]

Additionally, the southeastern region experiences hurricanes. During some years, hurricanes and the associated storm surges have caused extreme damage. For example, Hurricanes Katrina and Rita caused a loss of over 200 square miles of coastal land in Louisiana. [3] The 2005 hurricane season caused over 1,800 deaths and catastrophic damage to personal property and public infrastructure. [3]

Projected sea level rise, increased hurricane intensity, and associated storm surge may lead to further erosion, flooding, and property damage in the Southeast.

Two set of images show a significant decline in coastal land mass. The first set of images are dated 2001 and 2002. The second set was taken in 2005 and show the majority of the land submerged in water. View enlarged image

Chandeleur Islands, east of New Orleans, before and after 2005 hurricanes; 85% of the islands' above-water land mass was eliminated.
Source: USGCRP (2009)

  • Low-lying coastal communities that sit on subsiding land are especially sensitive to sea level rise. For example, a two foot increase in the average global sea level by 2100 would result in a 3.5 foot increase in sea level at Galveston, Texas. The land is sinking in Galveston and in many other areas along the central Gulf Coast. [3] For example, New Orleans, Louisiana faces a similar risk.
  • Sea level rise along the Southeast coast will likely erode wetlands and coastal shorelines. Low-lying areas would be flooded more frequently. Some ecosystems and communities could be permanently lost. [3]
  • Hurricanes gain strength over warm ocean waters. The destructive energy of Atlantic hurricanes has increased in recent decades. As the ocean surface continues to warm, hurricane intensity will likely continue to increase. [3] [5]
  • More frequent storm surge flooding of low-lying areas would cause more frequent flooding of transportation infrastructure. This can disrupt travel and damage roads, highways, bridges, oil and gas operations, and other structures in coastal areas. The transportation network is particularly vulnerable since many roads in the Gulf Coast region of the Southeast are at an elevation of four feet or less. [3]

For more information on climate change impacts on coasts, please visit the Coastal Impacts page.

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Subsidence in the Southeast
Aerial photograph of widespread flooding in a coastal cities. Houses, roads, and buildings are all inundated.

New Orleans, Louisiana, following Hurricane Katrina, showing Interstate 10, looking toward Lake Pontchartrain. This photo is from the U.S. Coast Guard's initial Hurricane Katrina damage assessment of New Orleans. Source: NRC (2010)

Many hydrologic alterations have been made to the Mississippi River to control flooding and improve access for shipping. Alterations include creating channels, dredging waterways, and erecting levees. However, these alterations have drastically decreased sediment flows to areas in the lower Mississippi Delta. These areas rely on sediment for land-building and replacing sediment lost to erosion. These factors, among others have contributed to subsidence — or sinking — of the land in areas like New Orleans.

Coastal areas in the Southeast are already sensitive to sea level rise and tropical storms. The added factor of subsidence will likely increase flooding risk due to storm surges.

During Hurricane Katrina, New Orleans suffered major flooding and loss of human life, property, and land. Changes in the area's hydrology, vegetation, and land, along with inadequate protective structures, contributed to these extensive impacts. Climate change may or may not have contributed to Hurricane Katrina, but this disaster is an example of how human-induced changes can exacerbate the vulnerability of coastal areas to the impacts of storm events.

Impacts on Water Resources

Water resource scarcity can affect many sectors of the Southeast's economy as well as the region's natural ecosystems. Periodic droughts, overconsumption of water resources, and other factors can create water shortages. Managing water resources will likely become more challenging with projected climate changes and anticipated population and economic growth.

  • Higher temperatures increase evaporation and water loss from plants. Projected increases in temperature will likely increase the frequency, duration, and intensity of droughts in the area. [3]
  • Projected changes in surface water runoff to the coast and groundwater recharge will likely allow saltwater to intrude and mix with shallow aquifers in some coastal areas of the Southeast, particularly in Florida and Louisiana. [3]
  • If the region increases groundwater pumping to offset water shortfalls, then aquifers will be further depleted. In the long term, the depletion of ground water supplies would place additional strain on surface water resources. [3]
  • Growth in demand will also likely strain water resources. The Southeast region is attracting a great deal of people, investment, and industry. The population of Florida has more than doubled during the past 30 years. Growth rates in most other southeastern states were 45% to 75% over the same period. Decreased water availability will challenge future growth and the quality of life of residents in the region. [3]

For more information on climate change impacts on water, please visit the Water Resources Impacts page.

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Impacts on Human Health

Two maps of the Southeast are shaded by colors that correspond to number of days per year in the two time periods: 1961 to 1979 and 2080 to 2099. During the first period, the number of days per year ranges from zero to 150 in a small portion Texas. The majority of the map shows under about 100 days per year. In the 2080 to 2099 map, only a few small portions of North Carolina have fewer than sixty days per year. Additionally, in this later period, the majority of the map shows about 150 days per year and large portions of Florida and Texas show about 180 days per year or more. View enlarged image

The maps show the number of days per year with peak temperatures above 90°F from 1961 to 1979 and projected for 2080 to 2099. By 2100, north Florida is projected to experience more than 165 days per year (over six months) over 90°F.
Source: USGCRP (2009)

Projected climate changes will stress human health.

  • Higher temperatures and more frequent heat waves will likely increase heat stress, respiratory illnesses, and heat-related deaths in the Southeast. High temperatures also correlate with poor air quality and pose a risk to people with respiratory problems. While the number of cold-related deaths is projected to decrease, net climate-related mortality will likely increase. [3]
  • Increased flooding and hurricanes could present extreme public health and emergency management challenges.
  • The spread of some types of bacteria has been linked to warmer temperatures. For example, food poisoning from eating shellfish infected with Vibrio parahaemolyticus bacteria has increased by 41% from 1996 to 2006 in the United States. As temperatures increase, the frequency of these types of shellfish-borne disease outbreaks in coastal waters is likely to increase. [3]

For more information on climate change impacts on human health, please visit the Human Health Impacts page.

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Impacts on Ecosystems

Warmer air and water temperatures, hurricanes, increased storm surges, and sea level rise will likely alter the Southeast's local ecosystems and agricultural productivity.

  • Warmer temperatures could increase the number of wildfires and pest outbreaks, such as the southern pine beetle. [3]
  • Declining soil moisture, water scarcity, and increasing temperatures will likely stress agricultural crops. [3]
  • Sustained temperatures between 90 and 100°F can significantly affect cattle. [3] Severe droughts, such as the water shortage that affected Texas in 2011, may lead to the premature slaughtering of cattle.
  • Sea level rise and increased storms will likely increase the salinity of estuaries, coastal wetlands, and tidal rivers. Rapid sea level rise could even eliminate some barrier islands that currently protect inland habitats. [3]

To learn more about climate change impacts on ecosystems, visit the Ecosystems Impacts page.

To learn more about what the Southeast is doing to adapt to climate change impacts, please visit the adaptation section of the Southeast Impacts and Adaptation page.

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References

[1] U.S. Census Bureau (2011). 2010 Census. Accessed 6/15/2011.

[2] NOAA (2011). Ocean and Coastal Resource Management in Your State: States and Territories Working With NOAA on Ocean and Coastal Management . National Oceanic and Atmospheric Administration. Accessed 6/15/2011.

[3] USGCRP (2009). Global Climate Change Impacts in the United States . Karl, T.R., J. M. Melillo, and T. C. Peterson (eds.). United States Global Change Research Program. Cambridge University Press, New York, NY, USA.

[4] CCSP (2008). Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I. A Report by the U.S. Climate Change Science Program and the Subcommittee on Global Change Research Savonis, M. J., V.R. Burkett, and J.R. Potter (eds.). Department of Transportation, Washington, DC, USA, 445 pp.

[5] NRC (2010). Advancing the Science of Climate Change . Exit EPA Disclaimer National Research Council. The National Academies Press, Washington, DC, USA.

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