Many types of extreme events related to climate change cause disruption of infrastructure, including power, water, transportation, and communication systems, that are essential to maintaining access to health care and emergency response services and safeguarding human health [High Confidence].

This finding is from chapter 4 of The Impacts of Climate Change on Human Health in the United States: A Scientific Assessment.

Process for developing key messages: The chapter was developed through technical discussions of relevant evidence and expert deliberation of the report authors at several workshops, teleconferences, and email exchanges. Authors considered inputs and comments submitted by the public, the National Academies of Sciences, and Federal agencies. For additional information on the overall report process, please see Appendices 2–3.

The health outcomes selected and prioritized for the chapter were based primarily on those that had substantial peer-reviewed literature to support statements. While many connections between changes in extreme events due to climate change and human health impacts appear intuitive, in some cases there may not be a robust body of peer-reviewed literature to support statements about direct effects. For example, while it is believed that droughts have the ability to impact water quality, which could in turn impact health, there are few studies documenting specific health consequences in the United States.f60a6281-fa30-444d-9acd-0d132a6d1683

In addition, due to space constraints, the authors did not intend to exhaustively identify all possible health impacts from every type of extreme event addressed in this chapter. Instead, the authors have provided an overview of possible impacts from different types of extreme events and provided a framework for understanding what additional factors (for example, population vulnerability, existing quality of infrastructure, etc.) can exacerbate or reduce adverse health outcomes.

Due to limited space and the uncertainty around future projections of tornadoes, we do not include detailed discussion of this topic in this chapter. We recognize that tornadoes can cause significant infrastructure damage and significant health impacts, and understanding how climate change will impact tornado intensity, frequency, and geographic distribution is an area of active scientific investigation.

Description of evidence base: The frequency, intensity, and duration of extreme events determines their physical impacts and the extent to which essential infrastructure is disrupted. There is strong, consistent evidence from multiple studies that infrastructure can either exacerbate or moderate the physical impacts of extreme events, influencing the ultimate nature and severity of health impacts. Projections of increasing frequency and/or intensity of some extreme events suggest that they pose threats to essential infrastructure, such as water, transportation, and power systems.089d8050-f4c8-4d07-bc35-25bf61691be3,686dd899-0f98-4423-ba29-fce90af74586,5a79e12b-b65c-40ef-8f80-7bcb04d57a1d,13d048c9-77d7-4bbb-beeb-ee49842d2719 Disruption of essential infrastructure and services after extreme events can increase population exposure to health hazards and reduce their adaptive capacity.089d8050-f4c8-4d07-bc35-25bf61691be3 There is substantial, high-quality literature supporting a finding that serious health risks can arise from utility outages; infrastructure and housing damage; and disruption or loss of access to sanitation, safe food and water supplies, health care, communication, and transportation.3be13957-eae2-4796-8504-ef2597b91b09,57f88e8c-2e4f-4e00-91e8-aea256ca3128,91c3ced0-65bc-43f7-b50c-11742eb657d5,c43fa066-6d7b-481b-9a85-22da8c27243a,53acdf32-e868-45b1-a669-83c0fa419f53,13d048c9-77d7-4bbb-beeb-ee49842d2719,dd072932-2da1-4e6c-b18a-6f7649969625,9a6c7a87-5c0f-4d64-904c-c707f68f2115,aa29148e-c86c-443d-9c1d-5a1d7fbc3437,ad3c4329-eac0-47ea-8342-be6ca602610c,eec8bc7b-93a6-4b99-92e7-18bf3e25bc9d,d887debf-59d6-423b-8f0f-433b49f9c9ca,858d9e98-4217-4278-92bf-d113e5561c39,692dfb63-86b7-4268-be18-725585651b27,3a569dc6-4596-488a-8c30-c0b6f884677f,81e4da11-12ba-4f0e-8bdb-ca6a8dadd63d,60be18ee-b5bc-4503-8f77-102561b193fb,e3439854-edb7-4acd-9e4f-b6ae0477f688

Infrastructure disruptions can have more or less impact on human health depending on the underlying vulnerability of the affected people and communities.089d8050-f4c8-4d07-bc35-25bf61691be3 Urban populations face unique exposure risks due to their dependence on complex, often interdependent infrastructure systems that can be severely disrupted during extreme events.dd5b893d-4462-4bb3-9205-67b532919566,df8dbdfc-912f-40b7-88a7-b3acbf026856 Rural communities also have vulnerabilities that are different from those faced by urban communities. For example, power and communications can take longer to restore after an outage.d57129df-a14f-4f92-9e8b-0140ee6672bb

Existing infrastructure is generally designed to perform at its engineered capacity assuming historical weather patterns, and these systems could be more vulnerable to failure in response to weather-related stressors under future climate scenarios.089d8050-f4c8-4d07-bc35-25bf61691be3,686dd899-0f98-4423-ba29-fce90af74586,a31abb74-51b0-46a9-a1db-cf9c708a457a Shifts in the frequency or intensity of extreme events outside their historical range pose infrastructure risks that may be compounded by the fact that much of the existing critical infrastructure in the United States, including water and sewage systems, roads, bridges, and power plants, are aging and in need of repair or replacement.089d8050-f4c8-4d07-bc35-25bf61691be3,5a79e12b-b65c-40ef-8f80-7bcb04d57a1d

New information and remaining uncertainties: Many of the uncertainties are similar to those of the previous key finding. There are few studies directly linking infrastructure impacts to health outcomes, and most are not longitudinal. Health impacts may occur after the event as a result of loss of infrastructure and public services. These impacts can be distributed over longer periods of time, making them harder to observe and quantify. Thus, the actual impact is likely underreported.

Uncertainties remain with respect to projecting how climate change will affect the severity of the physical impacts, including on infrastructure, of extreme events at smaller, more local scales and the timing of such impacts. Therefore, the subsequent impact on infrastructure also has a great deal of uncertainty. Thus, the key finding does not make any statements about future impacts. Instead the focus is on impacts that have occurred to date because there is supporting peer-reviewed literature. The extent to which infrastructure is exposed to extreme events, and the adaptive capacity of a community to repair infrastructure in a timely manner both influence the extent of the health outcomes. Thus, while the chapter makes general statements about trends in impacts due to extremes, there are uncertainties in the extent to which any specific location or infrastructure system could be impacted and the resulting health outcomes.

Assessment of confidence based on evidence: There is high confidence that many types of extreme events can cause disruption of essential infrastructure (such as water, transportation, and power systems), and that such disruption can adversely affect human health. Many qualitative studies have been published about the effects of these factors on health impacts from an extreme event (noted above), and the evidence is of good quality and consistent.