Climate change in our backyards:  the Southeast

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This third post in our series delving into Global Climate Change Impacts in the United States, a landmark report issued June 16, highlights the climate consequences we can expect to see in the southeastern region of the US.  This region is rich with culture, biodiversity, coastal and mountainous habitats, and a meandering coastline that twists and turns and harbors some of the most coveted beaches in the world.  But all of this is now at risk of being harmed, even devastated, by the harsh conditions that climate change brings.  The most severe impacts of climate change in the Southeast are most likely to be the projected increases in hurricane intensity and storm surge driven by rising air and ocean temperatures.  Recent hurricanes Katrina, Rita, Gustav, and Ike have given us a glimpse into such a future.  But other serious impacts are in store for these southern states as well.  See details.

A Changing Climate in the Southeastern US:  Highlights and Implications for US Preparedness

Our last post focused on the northeastern region of the US; the other seven regions in the report include the Midwest, Great Plains, Southwest, Northwest, Alaska, Islands, and Coasts.  The seven sectors discussed in the report are:  Water Resources, Energy Supply and Use, Transportation, Agriculture, Ecosystems, Human Health, and Society.

Resources:

Global Climate Change Impacts in the United States

USGCRP Fact Sheet for the Southeast

Union of Concerned Scientists (UCS):  Backgrounder on the Southeastern region

How is the climate changing in the southeastern US?  – some things to consider:

The southeastern US is rich with culture, biodiversity, coastal and mountainous habitats, and a meandering coastline that twists and turns and harbors some of the most coveted beaches in the world. But all of this is now at risk of being harmed, even devastated, by the harsh conditions that climate change brings.

>> “The most severe impacts of climate change in the Southeast are likely to be the projected increases in hurricane intensity and storm surge driven by rising air and ocean temperatures.”  We have already had a sampling of such a future with hurricanes Katrina, Rita, Gustav, Ike, and many others.

>> A hotter Southeast region also means “more heat-related illness; declines in forest growth and agricultural crop production due to the combined effects of heat stress and declining soil moisture; declines in cattle production; increased buckling of pavement and railways; and reduced oxygen levels in streams and lakes, leading to fish kills and declines in aquatic species diversity.”

>> “Decreased water availability due to increased temperature and longer periods of time between rainfall events, coupled with an increase in societal demand, is very likely to affect many sectors of the Southeast’s economy.”

>> The perceived high quality of life in the Southeast has contributed to its growing population in recent years.  Both factors are likely to be affected by the many challenges associated with climate change, such as “reduced insurance availability, increased insurance cost, and increases in water scarcity, sea-level rise, extreme weather events, and heat stress.”

Some specifics:

Temperature Increases

•  The region’s average annual temperature has risen by about 2° F since 1970, “with the greatest seasonal increase in temperature occurring during the winter months.”

•  “By the end of the century, average annual temperatures are projected to rise 4.5° F under a lower emissions scenario and 9° F under a higher emissions scenario.”

•  “Effects of increased heat include more heat-related illness; declines in forest growth and agricultural crop production due to the combined effects of heat stress and declining soil moisture; declines in
cattle production; increased buckling of pavement and railways; and reduced oxygen levels in streams and lakes, leading to fish kills and declines in aquatic species diversity.”

o “The warming projected for the Southeast during the next 50 to 100 years will create heat-related stress for people, agricultural crops, livestock, trees, transportation and other infrastructure, fish, and wildlife.”

o Temperature increases and spikes also translate to “increased illness and death due to greater summer heat stress, unless effective adaptation measures are implemented.”

o Southeastern states can also expect to see a “decline in forest growth and agricultural crop production due to the combined effects of thermal stress and declining soil moisture, increased buckling of pavement and railways, decline in dissolved oxygen in streams, lakes, and shallow aquatic habitats leading to fish kills and loss of aquatic species diversity, and decline in production of cattle and other rangeland livestock.”

Precipitation:  Droughts and Flooding

• The Southeast has already experienced changes in the frequency, distribution, and intensity of precipitation, a trend that is expected to continue.
o “Average autumn precipitation has increased by 30 percent for the region since 1901; heavy downpours have increased in many parts of the region, and the percentage of the region experiencing moderate to severe drought has risen over the past three decades.”

o Since the 1970s, “the area of moderate to severe spring and summer drought has increased by 12 percent and 14 percent, respectively.  Even in the fall months, when precipitation tended to increase in most of the region, the extent of drought increased by 9 percent.”

o   Climate models indicate that Gulf Coast states will tend to have less rainfall in winter and spring in relation to the more northern states in the region, and that droughts are likely to continue to increase in frequency, intensity, and duration.

•  “Decreased water availability due to increased temperature and longer periods of time between rainfall events, coupled with an increase in societal demand is very likely to affect many sectors of the Southeast’s economy.”

Sea Level Rise, Hurricanes, Storm Surges, and Coastal Flooding

•  Increased sea surface temperatures have been shown to make hurricanes more severe, and more energetic.

•  The report notes that “the destructive potential of Atlantic hurricanes has increased since 1970, correlated with an increase in sea surface temperature,” and that “the intensity of hurricanes is likely to increase during this century with higher peak wind speeds, rainfall intensity, and storm surge height and strength” … with an accompanying increase in “inland and coastal flooding, coastal erosion rates, wind damage to coastal forests, and wetland loss.”

•  A rise in average sea levels of up to 2 feet coupled with projected increases in hurricane intensity and associated storm surge “are likely to be among the most costly consequences of climate change for this region.”

•  Coastal vulnerability to hurricane damage is already quite high, and a rapid acceleration in the current rate of increase in sea level could further threaten a large portion of the Southeast coastal zone, exacerbating the “severe risk to people, personal property, and public infrastructure in the Southeast.”

•  “Current buildings and infrastructure were not designed to withstand the intensity of the projected storm surge, which would cause catastrophic damage.”

The report talks about adaptive measures, and building in resiliency in Southeastern communities:

“Three different types of adaptation to sea-level rise are available for low-lying coastal areas.  One is to move buildings and infrastructure farther inland to get out of the way of the rising sea.  Another is to accommodate rising water through changes in building design and construction, such as elevating building on stilts…The third adaptation option is to try to protect existing development by building levees and river flood control structures…In addition to levees, enhancement of key highways used as hurricane evacuation routes and improved hurricane evacuation planning is a common adaptation underway in all Gulf Coast states.  Other protection options that are being practiced along low-lying coasts include the enhancement and protection of natural features such as forested wetlands, saltmarshes, and barrier islands”

Ecosystem Responses

•  On of the most troubling warnings in the report is that the effects of crossing an ecological threshold could “cascade among both living and physical systems” with potentially dire and possibly irreversible consequences.

• Some ecological responses to climate change are expected to proceed rapidly, resulting in abrupt disturbances to ecosystems and to the resources they provide to people.  Examples include:

o “the sudden loss of coastal landforms that serve as a storm-surge barrier for natural resources and as a homeland for coastal communities (such as in a major hurricane);”

o “lower soil moisture and higher temperatures leading to intense wildfires or pest outbreaks in southeastern forests;”

o “intense droughts leading to the drying of lakes, ponds, and wetlands;”

o “local or global extinction of riparian and aquatic species.”

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