Increasing temperatures and the associated increase in frequency, intensity, and duration of extreme heat events will affect public health, natural and built environments, energy, agriculture, and forestry.

This finding is from chapter 17 of Climate Change Impacts in the United States: The Third National Climate Assessment.

Process for developing key messages: A central component of the process was the Southeast Regional Climate Assessment Workshop that was held on September 26-27, 2011, in Atlanta, with approximately 75 attendees. This workshop began the process leading to a foundational Technical Input Report (TIR). That 344-page foundational “Southeast Region Technical Report to the National Climate Assessment”4739fda9-9431-4cb3-8572-5f992fd61519 comprised 14 chapters from over 100 authors, including all levels of government, non-governmental organizations, and business. The writing team held a 2-day meeting in April 2012 in Ft. Lauderdale, engaged in multiple teleconference and webinar technical discussions, which included careful review of the foundational TIR,4739fda9-9431-4cb3-8572-5f992fd61519 nearly 60 additional technical inputs provided by the public, and other published literature and professional judgment. Discussions were followed by expert deliberation of draft key messages by the authors, and targeted consultation with additional experts by the Southeast chapter writing team and lead author of each key message.

Description of evidence base: The key message and supporting text summarize extensive evidence documented in the Southeast Technical Input Report.4739fda9-9431-4cb3-8572-5f992fd61519 Technical inputs (57) on a wide range of topics were also received and reviewed as part of the Federal Register Notice solicitation for public input. Numerous peer-reviewed publications describe increasing hazards associated with heat events and rising temperatures for the Southeast. The authors of a report on the Southeast climateb50d0bc7-8731-41e7-861c-b88b678f51d0 worked closely with the region’s state climatologists on both the climatology and projections for temperature and associated heat events. Evidence of rising temperatures and current impactsb00a1349-fb5f-4e2d-b1bc-cfceb0863de2 07b2dd38-4085-4184-a498-ec32526d710f f56ba5f3-5b39-48f1-ad20-f3c01cc8eefa is based on an extensive set of field measurements. There is considerable evidence of the effects of high air temperatures across a wide range of natural and managed systems in the Southeast. Increased temperatures affect human health and hospital admissions.b00a1349-fb5f-4e2d-b1bc-cfceb0863de2 07b2dd38-4085-4184-a498-ec32526d710f 0508d20d-b8a6-4cfa-b984-a357a3b837aa c275ae44-75e4-4974-81ea-fe7119474ffb Rising water temperatures also increase risks of bacterial infection from eating Gulf Coast shellfish2b04b041-511c-4b3f-9e44-70d0cfae3052 and increase algal blooms that have negative human health effects.db612cfb-eafa-45fc-8083-1606aa5c5801 3325ef64-347b-4c33-9289-9e05e905dcbe 659613d7-c0e0-4f84-88b9-7e18e9815bab bf92266b-c107-4d7c-9bbb-1e4a08fa0fc7 There is also evidence that there will be an increase in favorable conditions for mosquitoes that carry diseases.443fddc1-9737-4c6a-8291-83508bfb9643 Higher temperatures are detrimental to natural and urban environments, through increased wildfires in natural areas and managed forests1cba19cb-5a7a-4432-8311-70633478df81 a1a14740-236c-46da-b10b-08e1b1df8519 329e8eea-66b4-4a0d-9a4d-f2be776943b0 1a72beb2-f4a0-4db9-bac8-eac55cbf676d and increased invasiveness of some non-native plants.a3f38823-1fa8-4f49-bc35-9f76c724230e High temperatures also contribute to more roadway damage and deformities of transportation infrastructure such as railroad tracks and bridges (Ch. 5: Transportation).c41596dd-67b3-460a-8e7c-5b9e5c2a986a In addition, high temperatures increase net energy demand and costs, placing more stress on electricity generating plants and distribution infrastructure. Increasing temperatures in the Southeast cause more stresses on crop and livestock agricultural systems. Heat stress reduces dairy and livestock production0fd487bb-27ef-4b45-b7b0-5294ad11cfac and also reduces yields of various crops grown in this region (corn, soybean, peanuts, rice, and cotton).190f2677-f5e4-4015-862e-71e982509814 457227bf-a153-4910-bc43-f9de8b7dda8f

New information and remaining uncertainties: Since 2007, studies on impacts of higher temperatures have increased in many areas. Most of the publications cited above concluded that increasing temperatures in the Southeast will result in negative impacts on human health, the natural and built environments, energy, agriculture, and forestry. A key issue (uncertainty) is the detailed mechanistic responses, including adaptive capacities and/or resilience, of natural and built environments, the public health system, energy systems, agriculture, and forests to increasing temperatures and extreme heat events. Another uncertainty is how combinations of stresses, for example lack of water in addition to extreme heat, will affect outcomes. There is a need for more monitoring to document the extent and location of vulnerable areas (natural and human), and then research to assess how those impacts will affect productivity of key food and forest resources and human well-being. There is also a need for research that develops or identifies more resilient, adapted systems.

Assessment of confidence based on evidence: Increasing Temperatures: There is high confidence in documentation that projects increases in air temperatures (but not in the precise amount) and associated increases in the frequency, intensity, and duration of extreme heat events. Projections for increases in temperature are more certain in the Southeast than projections of changes in precipitation. Impacts of increasing temperatures: Rising temperatures and the substantial increase in duration of high temperatures (for either the low [B1] or high [A2] emissions scenarios) above critical thresholds will have significant impacts on the population, agricultural industries, and ecosystems in the region. There is high confidence in documentation that increases in temperature in the Southeast will result in higher risks of negative impacts on human health, agricultural, and forest production; on natural systems; on the built environment; and on energy demand. There is lower confidence in the magnitude of these impacts, partly due to lack of information on how these systems will adapt (without human intervention) or be adapted (by people) to higher temperatures, and partly due to the limited knowledge base on the wide diversity that exists across this region in climates and human and natural systems.

References :

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