A Closer Look at the Draft National Climate Assessment: Southeast Feeling Impacts, Future Predictions Point to Worsening Effects


[In this series, BNA’s climate blog takes a closer look at U.S. regions covered in the draft National Climate Assessment. In addition to the Southeast and Caribbean, region, the assessment covers the Northeast, Midwest, Great Plains, Southwest, Northwest, Alaska and the Arctic, and Hawaii and U.S. Affiliated Pacific States.]   

What’s the “take away” for the Southeast and Caribbean in the draft National Climate Assessment? Climate change is already impacting the region, which is “exceptionally” vulnerable to rising sea levels, extreme heat events, and decreased water availability.

While the draft contains dire predictions, for example, of stronger hurricanes and greater economic losses in the coming decades, it also found that the region, which includes the Caribbean, can greatly reduce the risks posed by climate change by collaborating with local, state, and federal officials to adapt and mitigate potential impacts.

Released by the National Climate Assessment and Development Advisory Committee Jan. 11, as detailed in an Energy and Climate Reportarticle, the draft will become an official federal document once it’s submitted to the National Science and Technology Council sometime this fall. The council is expected to review, modify, and approve a final draft by Jan. 30, 2014.

A national assessment on climate science and climate change impacts is due to Congress every four years under the Global Change Research Act of 1990. However, only two reports have been completed since the law passed, one in 2000 and the other in 2009.

The Southeast in the draft assessment includes Alabama, Arkansas, Florida, Georgia, Kentucky, Louisiana, Mississippi, North Carolina, South Carolina, Tennessee, Virginia, Puerto Rico, and the U.S. Virgin Islands.

Temperature, Precipitation, Sea-Level Rise
While temperatures could rise between 2 and 4 degrees Fahrenheit in most of the United States in the next few decades, according to the draft assessment, the temperature in the interior regions of the Southeast could rise by up to 10-degree Fahrenheit by 2100.

Meanwhile, temperatures in the Caribbean are likely to rise between 2 and 4 degrees Fahrenheit, and the temperature in the Southeast, as a whole, rise between 2 and-6 degrees Fahrenheit.

Extreme heat events also will likely increase, and the region is expected to see the highest increase in heat index numbers—a measure of comfort that combines temperature and humidity—than any other part of the country, the draft said.

Higher temperatures also will lead to more air pollution, putting vulnerable populations at risk for adverse health-related impacts. The region already has experienced an increase in the number of days of excessive heat, according to the draft assessment, especially Atlanta, Miami, New Orleans, and Tampa, resulting in an increase in the average number of deaths on those days.

Changes in precipitation are less certain, but the draft found that if greenhouse gas emissions remain at high levels, annual rainfall will decrease 10 percent in the far southern and western portions of the region and increase by about 5 percent in the Northeastern part.

Warming also is expected to cause fewer tropical storms globally, but the draft said to expect stronger force storms in the category 4 and 5 range due to climate change and natural variability. As for major tornados, better reporting makes it appear that they have increased in number, the draft said, but statistically significant trends have not been found.

As for sea-level, the global average is expected to rise between one and four feet by 2100. Portions of the Southeast are highly vulnerable, but the draft did not predict by how much they are expected to rise. Instead, the draft said it will depend on the particular area and whether and by how much the local land is sinking.

According to the draft assessment, major cities like New Orleans, with about half the population living below sea level; Charleston, S.C.; Miami; Tampa, Fla.; and San Juan, Puerto Rico are among the cities most at risk from rising sea levels that also is expected to accelerate saltwater intrusion into freshwater supplies.

Furthermore, economic losses of up to $14 billion per year already are occurring due to sea-level rise, hurricane winds, and land subsidence in counties and parishes in Alabama, Louisiana, Mississippi, and Texas, the draft said. By 2030, economic losses could reach $18 billion and up to $23 billion, with only a 3 percent increase in hurricane wind speed and a sea-level rise of six inches.

Energy Resources at Risk
Temperature and sea-level rise have the potential to affect onshore and offshore oil and gas production, according to the draft assessment. For example, infrastructure that is protected by barrier islands could be vulnerable to sea-level rise and storm surges.

An example of how climate change can affect the nation’s energy supply can be found in Louisiana. According to the draft, the only stretch of road—Highway 1 in Southern Louisiana—that leads to Port Fourchon, which supports 90 percent of the nation’s offshore oil and gas production, is “literally sinking” and increasingly is flooding even during low-level storms. Plans are in the works to elevate the stretch. In the meantime, the draft said a 90-day shutdown of the road would cost the nation $7.8 billion.

Water Availability  

Over the next several decades, net water supply in the Southeast is expected to decline, resulting in water conflicts among states, especially in the western part of the region, according to the draft assessment. The Caribbean also is expected to be exposed to severe water stress under all climate change scenarios.

Decreased water availability is likely to worsen as the fast-growing region continues to attract more people and industry and land-use change occurs, the draft said.

The Apalachiocola-Chattahoochee-Flint River Basin in Georgia is an example of where water conflict is now occurring and may be exacerbated by future climate change, the draft assessment said. The basin supplies water in three states for many competing uses, according to the draft, and is likely to experience more shortages, more frequent emptying, violation of environmental flow requirements, and less energy generation.

Responses Needed
Even though many uncertainties exist in the location, scale, and time of climate change impacts, and may make decisionmaking difficult, early response strategies may lead to less severe consequences, the draft said. For example, some utilities in the region are now taking sea-level rise into account when constructing new facilities and are diversifying water resources.

In another example, the draft assessment said Clayton County, Ga., water officials were able to maintain reservoirs at near capacity during the 2007-2008 drought, while Lake Lanier, the water supply for Atlanta, was at record lows. In addition to implementing efficiency and leak detection programs, Clayton County was able to weather the drought by constructing wetlands to filter treated water that recharges groundwater and supplies surface reservoirs.

Also, the draft highlighted the Southeast Florida Regional Compact, which represents Broward, Monroe, Miami-Dade, and Palm Beach counties, as an example of what can be done through a collaboration of county, state, and federal agencies.

The compact released a plan in October 2012, A Region Responds to a Changing Climate, that provides "regionally-consistent methodologies" for mapping sea-level rise impacts, assessing vulnerability, and understanding the sources of regional greenhouse gas emissions. The plan contains more than 100 recommendations with respect to mitigation and adaptation that can be implemented through regional collaboration.

According to the draft assessment, South Florida, which is most at risk from sea-level rise and flooding events, is responding to the threat by taking action in all three types of adaptation options: protect, accommodate, and retreat.