This website is the digital version of the 2014 National Climate Assessment, produced in collaboration with the U.S. Global Change Research Program.

For the official version, please refer to the PDF in the downloads section. The downloadable PDF is the official version of the 2014 National Climate Assessment.

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Welcome to the National Climate Assessment

The National Climate Assessment summarizes the impacts of climate change on the United States, now and in the future.

A team of more than 300 experts guided by a 60-member Federal Advisory Committee produced the report, which was extensively reviewed by the public and experts, including federal agencies and a panel of the National Academy of Sciences.

Explore the effects of climate change
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Infrastructure is being damaged by sea level rise, heavy downpours, and extreme heat; damages are projected to increase with continued climate change.

Explore infrastructure.



utility worker; worker inspecting damaged road; urban power outage; road washed out due to flooding

Infrastructure around the country has been compromised by extreme weather events and rising sea levels. Power outages and road and bridge damage are among the infrastructure failures that have occurred during these extreme events. A disruption in any one system affects others. For example, a failure of the electrical grid can affect everything from water treatment to public health.

Sea level rise, storm surge, and heavy downpours, in combination with the pattern of continued development in coastal areas, are increasing damage to U.S. infrastructure including roads, buildings, and industrial facilities, and are also increasing risks to ports and coastal military installations. Flooding along rivers, lakes, and in cities following heavy downpours, prolonged rains, and rapid melting of snowpack is exceeding the limits of flood protection infrastructure designed for historical conditions. Extreme heat is damaging transportation infrastructure such as roads, rail lines, and airport runways.

Key Message: Urbanization and Infrastructure Systems

Climate change and its impacts threaten the well-being of urban residents in all U.S. regions. Essential infrastructure systems such as water, energy supply, and transportation will increasingly be compromised by interrelated climate change impacts. The nation’s economy, security, and culture all depend on the resilience of urban infrastructure systems.

Key Message: Essential Services are Interdependent

In urban settings, climate-related disruptions of services in one infrastructure system will almost always result in disruptions in one or more other infrastructure systems.

Key Message: Social Vulnerability and Human Well-Being

Climate vulnerability and adaptive capacity of urban residents and communities are influenced by pronounced social inequalities that reflect age, ethnicity, gender, income, health, and (dis)ability differences.

Key Message: Trends in Urban Adaptation - Lessons from Current Adopters

City government agencies and organizations have started adaptation plans that focus on infrastructure systems and public health. To be successful, these adaptation efforts require cooperative private sector and governmental activities, but institutions face many barriers to implementing coordinated efforts.


flooded subway

New York City’s subway system, the nation’s busiest, sustained the worst damage in its 108 years of operation on October 29, 2012. Millions of people were left without service for at least a week. The damages from Superstorm Sandy are indicative of what powerful tropical storms and higher sea levels could bring more frequently in the future, and were very much in line with vulnerability assessments conducted over the past four years.1,2,3,4 The effects of the storm would have been far worse if local climate resilience strategies had not been in place. The City of New York and the Metropolitan Transportation Authority worked aggressively to protect life and property by stopping the operation of the city’s subway before the storm hit and moving the train cars out of low-lying, flood-prone areas. Catastrophic loss of life would have resulted if there had been subway trains operating in the tunnels when the storm struck.

Climate change poses a series of interrelated challenges to the country’s most densely populated places: its cities. The U.S. is highly urbanized, with about 80% of its population living in cities and metropolitan areas. Cities depend on infrastructure, like water and sewage systems, roads, bridges, and power plants, much of which is aging and in need of repair or replacement. These issues will be compounded by rising sea levels, storm surges, heat waves, and extreme weather events, stressing or even overwhelming essential services.

Urban dwellers are particularly vulnerable to disruptions in essential infrastructure services, in part because many of these infrastructure systems are reliant on each other. For example, electricity is essential to multiple systems, and a failure in the electrical grid can affect water treatment, transportation services, and public health. These infrastructure systems – lifelines to millions – will continue to be affected by various climate-related events and processes.

Cities have become early responders to climate change challenges and opportunities. Integrating climate change action in everyday city and infrastructure operations and governance is an important planning and implementation tool for advancing adaptation in cities.5,6 By integrating climate-change considerations into daily operations, these efforts can forestall the need to develop a new and isolated set of climate-change-specific policies or procedures.7 This strategy enables cities and other government agencies to take advantage of existing funding sources and programs, and achieve co-benefits in areas such as sustainability, public health, economic development, disaster preparedness, and environmental justice. Pursuing low-cost, no-regrets options is a particularly attractive short-term strategy for many cities.5,7

Key Message: Reliability and Capacity at Risk

The impacts from sea level rise and storm surge, extreme weather events, higher temperatures and heat waves, precipitation changes, Arctic warming, and other climatic conditions are affecting the reliability and capacity of the U.S. transportation system in many ways.

Key Message: Coastal Impacts

Sea level rise, coupled with storm surge, will continue to increase the risk of major coastal impacts on transportation infrastructure, including both temporary and permanent flooding of airports, ports and harbors, roads, rail lines, tunnels, and bridges.

Key Message: Weather Disruptions

Extreme weather events currently disrupt transportation networks in all areas of the country; projections indicate that such disruptions will increase.

Key Message: Costs and Adaptation Options

Climate change impacts will increase the total costs to the nation’s transportation systems and their users, but these impacts can be reduced through rerouting, mode change, and a wide range of adaptive actions.


Transportation systems are affected by climate change and also contribute to climate change. In 2010, the U.S. transportation sector accounted for 27% of all U.S. heat-trapping greenhouse gas emissions, with cars and trucks accounting for 65% of that total.9 Petroleum accounts for 93% of the nation’s transportation energy use.9 This means that policies and behavioral changes aimed at reducing greenhouse gas emissions will have significant implications for the various components of the transportation sector.

Gulf Coast Transportation Hubs at Risk Gulf Coast Transportation Hubs at Risk Details/Download

Transportation systems are already experiencing costly climate change related impacts. Many inland states, including Vermont, Tennessee, Iowa, and Missouri, have experienced severe precipitation events, hail, and flooding during the past three years, damaging roads, bridges, and rail systems and the vehicles that use them. Over the coming decades, all modes of transportation and regions will be affected by increasing temperatures, more extreme weather events, and changes in precipitation. Concentrated transportation impacts are particularly expected to occur in Alaska and along seacoasts.

Key Message: Disruptions from Extreme Weather

Extreme weather events are affecting energy production and delivery facilities, causing supply disruptions of varying lengths and magnitudes and affecting other infrastructure that depends on energy supply. The frequency and intensity of certain types of extreme weather events are expected to change.

Key Message: Climate Change and Seasonal Energy Demands

Higher summer temperatures will increase electricity use, causing higher summer peak loads, while warmer winters will decrease energy demands for heating. Net electricity use is projected to increase.

Key Message: Implications of Less Water for Energy Production

Changes in water availability, both episodic and long-lasting, will constrain different forms of energy production.

Key Message: Sea Level Rise and Infrastructure Damage

In the longer term, sea level rise, extreme storm surge events, and high tides will affect coastal facilities and infrastructure on which many energy systems, markets, and consumers depend.

Key Message: Future Energy Systems

As new investments in energy technologies occur, future energy systems will differ from today’s in uncertain ways. Depending on the character of changes in the energy mix, climate change will introduce new risks as well as opportunities.


The U.S. energy system provides a secure supply of energy with only occasional interruptions. However, projected impacts of climate change will increase energy use in the summer and pose additional risks to reliability. Extreme weather events and water shortages are already interrupting energy supply and impacts are expected to increase in the future. Most vulnerabilities and risks to energy supply and use are unique to local situations; others are national in scope.

Increase in Cooling Demand and Decrease in Heating Demand

Increase in Cooling Demand and Decrease in Heating Demand


The observed increase in cooling energy demand has been greater than the decrease in heating energy demand. Figure shows observed increases in population-weighted cooling degree days, which result in increased air conditioning use, and decreases in population-weighted heating degree days, meaning less energy required to heat buildings in winter, compared to the average for 1970-2000. Cooling degree days are defined as the number of degrees that a day’s average temperature is above 65ºF, while heating degree days are the number of degrees a day’s average temperature is below 65ºF. (Data from NOAA NCDC 201210).


Increases in average temperatures and high temperature extremes are expected to lead to increasing demands for electricity for cooling in every U.S. region. Virtually all cooling load is handled by the electrical grid. In order to meet increased demands for peak electricity, additional generating and distribution facilities will be needed, or demand will have to be managed through a variety of mechanisms. Electricity at peak demand typically is more expensive to supply than at average demand.11

In addition to being vulnerable to the effects of climate change, electricity generation is a major source of the heat-trapping gases that contribute to climate change. As a result, regulatory or policy efforts aimed at reducing emissions would also affect the energy supply system.


  1. ,, 2011: Inventory of U.S. Greenhouse Gas Emissions and Sinks: 2000 – 2009. EPA 430-R-11-005. 459 pp., U.S. Environmental Protection Agency, Washington, D.C. URL | Detail

  2. Foster, J., S. Winkelman, and A. Lowe, 2011: Lessons Learned on Local Climate Adaptation from the Urban Leaders Adaptation Initiative. 23 pp., The Center for Clean Air Policy, Washington, D.C. URL | Detail

  3. Jacob, K., C. Rosenzweig, R. Horton, D. Major, and V. Gornitz, 2008: MTA Adaptations to Climate Change: A Categorical Imperative. 48 pp., State of New York, Metropolitan Transportation Authority, New York, NY. URL | Detail

  4. Kafalenos, R. S., K. J. Leonard, D. M. Beagan, V. R. Burkett, B. D. Keim, A. Meyers, D. T. Hunt, R. C. Hyman, M. K. Maynard, B. Fritsche, R. H. Henk, E. J. Seymour, L. E. Olson, J. R. Potter, and M. J. Savonis, 2008: Ch. 4: What are the implications of climate change and variability for Gulf Coast transportation? Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Study, Phase I. A report by the U.S. Climate Change Science Program and the Subcommittee on Global Change Research. Final Report of Synthesis and Assessment Produ, M.J. Savonis, Burkett, V.R., and Potter, J.R., Eds., U.S. Department of Transportation. URL | Detail

  5. ,, 2012: Heating & Cooling Degree Day Data. NOAA’s National Climatic Data Center. URL | Detail

  6. ,, 2010: Report to the Legislature. 102 pp., New York State Department of Environmental Conservation, Albany, NY. URL | Detail

  7. ,, 2011: Responding to Climate Change in New York State: The ClimAID Integrated Assessment for Effective Climate Change Adaptation in New York State. Vol. 1244C. Rosenzweig, Solecki, W., DeGaetano, A., O'Grady, M., Hassol, S., and Grabhorn, P., Eds. Blackwell Publishing, 649 pp. URL | Detail

  8. ,, 2010: Adapting to Impacts of Climate Change. America’s Climate Choices: Report of the Panel on Adapting to the Impacts of Climate Change. National Research Council. The National Academies Press, 292 pp. URL | Detail

  9. Rosenzweig, C., W. Solecki, S. A. Hammer, and S. Mehrotra, 2010: Cities lead the way in climate-change action. Nature, 467, 909-911, doi:10.1038/467909a. URL | Detail

  10. Wilbanks, T., D. Bilello, D. Schmalzer, and M. Scott, 2012: Climate Change and Energy Supply and Use. Technical Report to the U.S. Department of Energy in Support of the National Climate Assessment. 79 pp., Oak Ridge National Laboratory, U.S. Department of Energy, Office of Science, Oak Ridge, TN. URL | Detail

  11. Zimmerman, R., and C. Faris, 2010: Infrastructure impacts and adaptation challenges. Annals of the New York Academy of Sciences, 1196, 63-86, doi:10.1111/j.1749-6632.2009.05318.x. | Detail

The National Climate Assessment summarizes the impacts of climate change on the United States, now and in the future.

A team of more than 300 experts guided by a 60-member Federal Advisory Committee produced the report, which was extensively reviewed by the public and experts, including federal agencies and a panel of the National Academy of Sciences.

United States Global Change Research Program logo United States Global Change Research Program participating agency logos