Adapted from:Global Climate Impacts in the United States. T.R. Karl, J.M. Mellilo, and T.C. Peterson (eds.). Cambridge University Press, 2009. Available online at USGCRP
The Southeast region serves as an example of how rising temperatures can be associated with both increased drought and an increased frequency of downpours and other intense precipitation events. Southeast annual average temperature has risen 2 degrees Fahrenheit since 1970, with the greatest seasonal increase in the winter months. From 1901 to 2008, there was a 30 percent increase in fall precipitation over most of the region but a decrease in fall precipitation in South Florida. Since 1970, when temperatures began an upward trend, spring precipitation has declined by about 30 percent, while annual precipitation has decreased by about 8 percent in the region as a whole. The percentage of the Southeast in moderate to severe drought increased over the past three decades, even as there has been an increase in heavy downpours. The power of Atlantic hurricanes has increased since 1970, associated with an increase in sea surface temperature.
Projections call for continued warming, with the greatest temperature increases in summer. The number of very hot days is projected to rise at a faster rate than average temperatures. Average annual temperatures are projected to rise 4.5 degrees Fahrenheit under a scenario of lower emissions of greenhouse gases and 9 degrees Fahrenheit given higher greenhouse gas emissions, with a 10.5-degree Fahrenheit increase in summer and a much higher heat index. Sea-level rise is projected to accelerate, increasing coastal inundation and shoreline retreat. The intensity of hurricanes is likely to increase, with higher wind speeds, rainfall intensity, and storm surge height and strength.
Key issues include:
Heat-related stresses for people, plants, and animals will increase. Effects of higher air and water temperatures are many. They include more heat-related illness. Heat stress, coupled with declining soil moisture, could also reduce productivity of forests, crops, and cattle. Increased buckling of pavement and railways could create more transportation challenges. Reduced oxygen levels in streams and lakes, associated with higher water temperatures, could lead to fish kills and declines in aquatic species diversity.
Decreased water availability is very likely. Increasing temperatures and longer periods between rainfall events coupled with increased demand for water is expected to result in decreased water availability. This is very likely to affect the region’s economy as well as its natural systems. The 2007 water shortage in the Atlanta area created serious conflicts among three states, the U.S. Army Corps of Engineers (which operates the dam at Lake Lanier), and the U.S. Fish and Wildlife Service (which is charged with protecting endangered species). Such competition for limited water supplies is expected to continue as the climate warms.
Sea levels are projected to rise, and hurricane intensity and associated storm surge is projected to increase. Low-lying areas, including some communities, will be inundated more frequently — some permanently — by the advancing sea. Hurricanes Katrina and Rita in 2005 led to the loss of 217 square miles of land as well as more than 1,800 lives. Current buildings and infrastructure were not designed to withstand the intensity of the storm surge projected for the future, so catastrophic damage could result. If sea-level rise increases at an accelerated rate as ice sheets respond to the warming, a large portion of the Southeast coastal zone could be threatened. These issues will be among the most serious consequences of climate change.
Ecological thresholds are likely to be crossed throughout the region. Abrupt changes to ecosystems may occur as climate changes. For instance, hurricanes may destroy landforms that serve as storm surge barriers and even inundate homes in some coastal communities. Ecosystems provide numerous important services that have high economic and cultural value in the Southeast, so these disruptions could reduce the quality and quantity of the benefits affected ecosystems provide to people.
Quality of life will be affected by the above issues and reduced availability of insurance for at-risk properties. Increasing heat stress, water scarcity, and severe weather events will affect quality of life for the regional population, as will the reduced availability of affordable insurance for at-risk properties. The Southeast “sunbelt” has attracted people, industry, and investment. The population of Florida has increased by 100 percent during the past three decades, and growth rates in most other southeastern states were between 45 and 75 percent. The challenges associated with climate change will affect the quality of life for these residents and affect future population growth.
Adapted by Melanie Lenart, University of Arizona
Other Regional Climate Change Impacts from USGCRP: