Fifth National Climate Assessment

U.S. Global Change Research Program

The Fifth National Climate Assessment

The Fifth National Climate Assessment is the US Government’s preeminent report on climate change impacts, risks, and responses. It is a congressionally mandated interagency effort that provides the scientific foundation to support informed decision-making across the United States.

How the United States Is Addressing Climate Change

The effects of human-caused climate change are already far-reaching and worsening across every region of the United States. Rapidly reducing greenhouse gas emissions can limit future warming and associated increases in many risks. Across the country, efforts to adapt to climate change and reduce emissions have expanded since 2018, and US emissions have fallen since peaking in 2007. However, without deeper cuts in global net greenhouse gas emissions and accelerated adaptation efforts, severe climate risks to the United States will continue to grow.

Future climate change impacts depend on choices made today

The more the planet warms, the greater the impacts. Without rapid and deep reductions in global greenhouse gas emissions from human activities, the risks of accelerating sea level rise, intensifying extreme weather, and other harmful climate impacts will continue to grow. Each additional increment of warming is expected to lead to more damage and greater economic losses compared to previous increments of warming, while the risk of catastrophic or unforeseen consequences also increases. {2.3, 19.1}

However, this also means that each increment of warming that the world avoids—through actions that cut emissions or remove carbon dioxide (CO₂) from the atmosphere—reduces the risks and harmful impacts of climate change. While there are still uncertainties about how the planet will react to rapid warming, the degree to which climate change will continue to worsen is largely in human hands. {2.3, 3.4}

In addition to reducing risks to future generations, rapid emissions cuts are expected to have immediate health and economic benefits (Figure 1.1). At the national scale, the benefits of deep emissions cuts for current and future generations are expected to far outweigh the costs. {2.1, 2.3, 13.3, 14.5, 15.3, 32.4; Ch. 2, Introduction}

A multipanel infographic illustrates climate change risks and opportunities in the United States. At top left, five maps of the United States divided into the 10 National Climate Assessment regions show examples of how climate change is happening now. The maps show directions of observed changes at the regional scale for several metrics as described in the caption. At top middle, text and icons indicate that each additional increment of warming leads to greater risks to water supply, food security, infrastructure, health and well-being, ecosystems, the economy, and livelihoods and heritage. At top right, a heading notes that without deeper cuts in global net emissions, climate risks to the US will continue to grow. Below this, a grouped bar chart shows how many more climate hazards a person born in North America in 2020 will experience during their lifetime, on average, compared to a person born in 1965. The y-axis shows the number of additional events as a multiplier, ranging from 0 to 5 times as many events. For each of six climate hazards, color-coded bars are used to indicate projected multipliers for three different levels of global warming above preindustrial levels: 2.7, 4.3, and 6.3 degrees Fahrenheit, indicated by the colors yellow, orange, and red, respectively. For each hazard, bars are arranged by increasing warming level from left to right. Numbers above each bar give the specific multiplier value. The projected multipliers for each hazard are as follows: Wildfires, 1.3, 1.6, and 1.6. River floods, 0.8, 1.4, and 1.7. Crop failure: 1.0, 1.0, and 1.1. Tropical cyclones, 1.2, 2.1, and 2.2. Drought, 1.4, 2.1, and 2.0. Heatwaves, 2.1, 3.8, and 4.7. At bottom left, text and a climate stripes chart show that how much more the US warms depends on choices made today. Text indicates that future global greenhouse emissions from human activities determine whether and how quickly the US reaches warming levels associated with greater risks. As described in the caption, the climate stripes in shades of blue, yellow, orange, and red show observed warming for 1951 to 2022 and projected warming through 2100 for the five main scenarios discussed elsewhere in the Overview. Warming is much larger and occurs sooner for higher scenarios. Bottom right, text and icons note that action to limit future warming and reduce risks can have near-term benefits with opportunities, with the following examples: low-carbon energy jobs, improved air quality, health benefits, economic benefits, reduced risks to ecosystems, reduced risks to biodiversity, more options for adaptation, and social benefits.

Climate change presents risks while action to limit warming and reduce risks presents opportunities for the US.

Figure 1.1. (top left) Changes in multiple aspects of climate are apparent in every US region. The five maps present observed changes for five temperature, precipitation, and sea level rise metrics: 1) warming is apparent in every region (based on changes in annual average temperature in 2002–2021 compared to the 1901–1960 average for the contiguous United States, Hawaiʻi, and Puerto Rico and to 1925–1960 for Alaska); 2) the number of warm nights per year (days with minimum temperatures at or above 70°F in 2002–2021 compared to 1901–1960) is increasing everywhere except the Northern Great Plains, where they have decreased, and in Alaska, where nights above 70°F are not common; 3) average annual precipitation is increasing in most regions, except in the Northwest, Southwest, and Hawai‘i, where precipitation has decreased (same time periods as annual average temperature); 4) heavy precipitation events are increasing everywhere except Hawai‘i and the US Caribbean, where there has been a decrease (trends over the period 1958–2021); and 5) relative sea levels are increasing along much of the US coast except in Oregon, Washington, and Alaska, where there is a mix of both increases and decreases (trends over 1990–2020). {2.2, 9.1; Figures 2.4, 2.5, 2.7, 2.8}

(top center) Every fraction of a degree of additional warming will lead to increasing risks across multiple sectors in the US (see Table 1.2 and “Current and Future Climate Risks to the United States” below). Without rapid, substantial reductions in the greenhouse gases that cause global warming, these climate risks in the US are expected to increase.

(top right) People born in North America in 2020, on average, will be exposed to more climate-related hazards compared to people born in 1965. How many more extreme climate events current generations experience compared to previous generations will depend on the level of future warming. {Figure 15.4}

(bottom left) This climate stripes chart shows the observed changes in US annual average surface temperature for 1951–2022 and projected changes in temperature for 2023–2095 for five climate scenarios, ranging from a very high scenario, where greenhouse gas emissions continue to increase through most of the century, to a very low scenario, where emissions decline rapidly, reaching net zero by around midcentury (see Figure 1.4 and Table 3 in the Guide to the Report). Each vertical stripe represents the observed or projected change in temperature for a given year compared to the 1951–1980 average; changes are averaged over all 50 states and Puerto Rico but do not include data for the US-Affiliated Pacific Islands and the US Virgin Islands (see also Figure 1.13).

(bottom right) Although climate benefits from even the most aggressive emissions cuts may not be detectable before the middle of the century, there are many other potential near-term benefits and opportunities from actions that reduce greenhouse gas emissions. {2.3, 8.3, 10.3, 13.3, 14.5, 15.3, 19.1, 31.3, 32.4}

Figure credits: (top left, top center, top right, bottom right) USGCRP, USGCRP/ICF, NOAA NCEI, and CISESS NC; (bottom left) adapted from panel (c) of Figure SPM.1 in IPCC 2023.

US emissions have decreased, while the economy and population have grown

Annual US greenhouse gas emissions fell 12% between 2005 and 2019. This trend was largely driven by changes in electricity generation: coal use has declined, while the use of natural gas and renewable technologies has increased, leading to a 40% drop in emissions from the electricity sector. Since 2017, the transportation sector has overtaken electricity generation as the largest emitter. {11.1, 13.1, 32.1; Figures 32.1, 32.3}

As US emissions have declined from their peak in 2007, the country has also seen sustained reductions in the amount of energy required for a given quantity of economic activity and the emissions produced per unit of energy consumed. Meanwhile, both population and per capita GDP have continued to grow. {32.1; Figures 32.1, 32.2}

Recent growth in the capacities of wind, solar, and battery storage technologies is supported by rapidly falling costs of zero- and low-carbon energy technologies, which can support even deeper emissions reductions. For example, wind and solar energy costs dropped 70% and 90%, respectively, over the last decade, while 80% of new generation capacity in 2020 came from renewable sources (Figures 1.2, 1.3). {5.3, 12.3, 32.1, 32.2; Figure A4.17}

Across all sectors, innovation is expanding options for reducing energy demand and increasing energy efficiency, moving to zero- and low-carbon electricity and fuels, electrifying energy use in buildings and transportation, and adopting practices that protect and improve natural carbon sinks that remove and store CO₂ from the atmosphere, such as sustainable agricultural and land-management practices. {11.1, 32.2, 32.3; Boxes 32.1, 32.2; Focus on Blue Carbon}

Six time series bar charts show historical trends in the unit costs and capacity of low-carbon energy technologies in the United States, as described in the caption. The top left and top center graphs show the average levelized cost of energy (abbreviated LCOE) for wind and solar, respectively, from 2010 to 2020. Y-axis values for both graphs range from 0 to 240 dollars per megawatt-hour. Average wind LCOE shows a gradual decrease over the time period from about 90 to just under 40 dollars per megawatt-hour, while average solar LCOE shows a steep decrease from about 220 to 130 dollars between 2010 and 2012 and then a steady decrease to about 30 dollars in 2020. The top right graph shows average electric vehicle (abbreviated EV) battery cost from 2010 to 2022. Y-axis values range from 0 to 1,000 dollars per kilowatt-hour. EV battery costs show a steep decline from about 1,000 dollars per kilowatt-hour in 2010 to about 500 dollars in 2012, followed by a slower decrease to less than 200 dollars in 2022. The bottom left graph shows cumulative onshore wind capacity from 2010 to 2020. Y-axis values range from 0 to 140 gigawatts. Between 2010 and 2020, cumulative wind capacity shows a steady increase from about 40 to about 120 gigawatts. The bottom center graph shows cumulative US utility-scale solar capacity from 2010 to 2021. Y-axis values range from 0 to 40 gigawatts. Between 2010 and 2015, cumulative solar capacity shows a gradual increase from nearly 0 to about 8 gigawatts and then increases rapidly to about 38 gigawatts by 2021. The bottom right graph shows cumulative US EV sales from 2010 to 2022. Y-axis values range from 0 to 3.5 million vehicles. Cumulative EV sales increase from 0 in 2010 to more than 1 million units in 2018 and then increase much more rapidly to about 3.25 million in 2022.

Increasing capacities and decreasing costs of low-carbon energy technologies are supporting efforts to further reduce emissions.

Figure 1.2. Costs of onshore wind (a), solar photovoltaics (b), and electric vehicle (EV) batteries (c) have decreased sharply since 2000 (data shown here start in 2010), as the cumulative capacities of wind and solar generation (d and e) and the cumulative number of EVs sold (f) have increased. {Figure 32.8} Figure credit: Electric Power Research Institute, National Renewable Energy Laboratory, NOAA NCEI, and CISESS NC.

Accelerating advances in adaptation can help reduce rising climate risks

As more people face more severe climate impacts, individuals, organizations, companies, communities, and governments are taking advantage of adaptation opportunities that reduce risks. State climate assessments and online climate services portals are providing communities with location- and sector-specific information on climate hazards to support adaptation planning and implementation across the country. New tools, more data, advancements in social and behavioral sciences, and better consideration of practical experiences are facilitating a range of actions (Figure 1.3). {7.3, 12.3, 21.4, 25.4, 31.1, 31.5, 32.5; Table 31.1}

Actions include:

Implementing nature-based solutions—such as restoring coastal wetlands or oyster reefs—to reduce shoreline erosion {8.3, 9.3, 21.2, 23.5}
Upgrading stormwater infrastructure to account for heavier rainfall {4.2}
Applying innovative agricultural practices to manage increasing drought risk {11.1, 22.4, 25.5}
Assessing climate risks to roads and public transit {13.1}
Managing vegetation to reduce wildfire risk {5.3}
Developing urban heat plans to reduce health risks from extreme heat {12.3, 21.1, 28.4}
Planning relocation from high-risk coastal areas {9.3}

Despite an increase in adaptation actions across the country, current adaptation efforts and investments are insufficient to reduce today’s climate-related risks and keep pace with future changes in the climate. Accelerating current efforts and implementing new ones that involve more fundamental shifts in systems and practices can help address current risks and prepare for future impacts (see “Mitigation and adaptation actions can result in systemic, cascading benefits” below). {31.1, 31.3}

Climate action has increased in every region of the US

Efforts to adapt to climate change and reduce net greenhouse gas emissions are underway in every US region and have expanded since 2018 (Figure 1.3; Table 1.1). Many actions can achieve both adaptation and mitigation goals. For example, improved forest- or land-management strategies can both increase carbon storage and protect ecosystems, and expanding renewable energy options can reduce emissions while also improving resilience. {31.1, 32.5}

A horizontal bar chart shows adaptation and mitigation actions taken across the US, as described in the caption. At left are the US states and territories grouped by National Climate Assessment region. Green bars extending to the left of the central vertical axis show the number of state and city-level adaptation actions, on an axis ranging from 0 at center to 350 from right to left. Blue bars to the right of the axis show the number of state-level mitigation actions, and circles show the number of city-level actions, with x-axis values ranging from 0 to 45. For both types of actions, lighter shading shows the number of actions through 2018 while darker shading shows the additional actions since 2018. Adaptation action counts are generally less than 50, except for Maryland, Massachusetts, Louisiana, Virginia, Oregon, and Washington, which have between 50 and 100, and three states with more than 100: New York (about 140), Florida (about 100), and California (more than 300). State-level mitigation action counts generally range from 5 to 10, with city-level numbers ranging between 0 and 10. Some regions or states show higher numbers, as follows: In the Northeast, every state shows at least 15 actions except for West Virginia at about 7. In the Southeast, Florida, North Carolina, and South Carolina have between 10 and 15 state-level actions, while Virginia has about 18. Florida also shows more than 20 city-level actions. In the Midwest, Illinois, Iowa, Minnesota, Ohio, and Wisconsin show between 15 and 20 actions. In the Northern Great Plains, Montana has about 13 state-level actions, but there are zero city-level actions in the region. In the Southern Great Plains, Oklahoma and Texas have between 10 and 15 state-level actions. In the Southwest, all states have at least 15 state-level actions except for Utah, with about 13. The state of Hawaii shows more than 20 actions and about 2 city-level actions.

Cities and states are acting on climate change, with a substantial increase in new activities underway since 2018.

Figure 1.3. Since 2018, city- and state-level adaptation plans and actions (green bars, left) increased by 32%, complemented by a 14% increase in the total number of new state-level mitigation activities (blue bars, right; 69% have updated their policies). In 2021 there were 271 city-level mitigation actions in place (open circles, right), according to the Global Climate Action Tracker. Renewable energy and energy efficiency projects on Tribal lands have also expanded (not shown). {31.1, 32.5; Figure 16.4; Table 1.1} Figure credit: US Army Corps of Engineers, EPA, Pennsylvania State University, NOAA NCEI, and CISESS-NC.

Climate adaptation and mitigation efforts involve trade-offs, as climate actions that benefit some or even most people can result in burdens to others. To date, some communities have prioritized equitable and inclusive planning processes that consider the social impacts of these trade-offs and help ensure that affected communities can participate in decision-making. As additional measures are implemented, more widespread consideration of their social impact can help inform decisions around how to distribute the outcomes of investments. {12.4, 13.4, 20.2, 21.3, 21.4, 26.4, 27.1, 31.2, 32.4, 32.5; Box 20.1}

Table 1.1. Climate Actions Are Taking Place Across All US Regions

Examples of recent local adaptation, resilience, and mitigation actions around the country follow.

Region	Action
Northeast	The 2022 stormwater code in Pittsburgh, Pennsylvania, requires new developments to plan for projected increases in heavy rainfall under climate change rather than building to historical rainfall amounts. In 2021, the city also committed to achieve carbon neutrality by 2050. {Box 21.1}
Southeast	Following repeated flooding from multiple hurricanes, measures to reduce flood risk in Princeville, North Carolina, include buyouts, elevating homes, and building housing that meets local flood standards. In Orlando, Florida, the city and businesses are adopting commercial building energy-efficiency requirements and electric vehicle readiness policies and have used wastewater and food scraps from parks and resorts to generate renewable biogas. {Boxes 22.1, 32.3}
US Caribbean	Many community-based organizations in Puerto Rico have undertaken actions to advance adaptation, social transformation, and sustainable development. These organizations work to expand renewable energy and equitable access to energy resources, prepare for disasters, restore ecosystems, strengthen agriculture and food security, and protect public health. {23.5}
Midwest	A wetland creation project in Ashtabula, Ohio, restored habitat displaced by shoreline development, improving coastal protection for the port on Lake Erie. In Michigan, some state forestlands are being managed to bolster carbon storage and to support recreation and wildlife habitat. {24.2, 24.4; Figure 24.9}
Northern Great Plains	The Nebraska Natural Resources Conservation Service supported farmers in testing soil health and evaluating soil management practices that promote climate adaptation. Across the region, wind electricity generation tripled between 2011 and 2021, with a growing number of Tribes leading the Nation’s renewable energy transition by installing wind, solar, and hydropower. {25.3, 25.5; Box 25.3}
Southern Great Plains	Texas- and Kansas-based groups are supporting soil and land management practices that increase carbon storage while protecting important ecosystems. Wind and solar energy generation and battery storage capacities have also grown, with the region accounting for 42% of national wind-generated electricity in 2022. {26.2}
Northwest	The Confederated Tribes of the Colville Reservation are prioritizing carbon capture in their forest and timber management efforts, leading to improved air and water quality and wildlife habitat as well as preservation of cultural areas and practices. {27.3}
Southwest	In response to severe drought, seven Colorado River basin states, the US and Mexican governments, and Indigenous Peoples are collaborating to improve water conservation and develop adaptation solutions. Dozens of cities are committed to emissions reductions; for instance, Phoenix is on track to meet a 2030 goal of 50% reduction in greenhouse gas emissions from 2018 levels. {Ch. 28, Introduction; Box 28.1}
Alaska	To address climate threats to traditional foods, the Chugach Regional Resources Commission is integrating Indigenous Knowledge and Western scientific methods in its adaptation efforts, including weekly water sampling for harmful algal blooms and restoring clam populations. Kelp farming is also being developed to reduce the effects of ocean acidification, serve as a carbon sink, and generate income. {29.7; Box 29.7}
Hawai‘i and US-Affiliated Pacific Islands	The Kauaʻi Island Utility Cooperative achieved a 69.5% renewable portfolio standard in 2021, and the island is occasionally 100% renewably powered during midday hours; it is projected to achieve a 90% renewable portfolio by 2026. Guam, the Republic of the Marshall Islands, the Federated States of Micronesia, and Palau plan to use blue carbon ecosystems to offset emissions while also protecting coastal infrastructure. {30.3; Box 30.3}

Meeting US mitigation targets means reaching net-zero emissions

The global warming observed over the industrial era is unequivocally caused by greenhouse gas emissions from human activities—primarily burning fossil fuels. Atmospheric concentrations of carbon dioxide (CO₂)—the primary greenhouse gas produced by human activities—and other greenhouse gases continue to rise due to ongoing global emissions. Stopping global warming would require both reducing emissions of CO₂ to net zero and rapid and deep reductions in other greenhouse gases. Net-zero CO₂ emissions means that CO₂ emissions decline to zero or that any residual emissions are balanced by removal from the atmosphere. {2.3, 3.1; Ch. 32}

Once CO₂ emissions reach net zero, the global warming driven by CO₂ is expected to stop: additional warming over the next few centuries is not necessarily “locked in” after net CO₂ emissions fall to zero. However, global average temperatures are not expected to fall for centuries unless CO₂ emissions become net negative, which is when CO₂ removal from the atmosphere exceeds CO₂ emissions from human activities. Regardless of when or if further warming is avoided, some long-term responses to the temperature changes that have already occurred will continue. These responses include sea level rise, ice sheet losses, and associated disruptions to human health, social systems, and ecosystems. In addition, the ocean will continue to acidify after the world reaches net-zero CO₂ emissions, as it continues to gradually absorb CO₂ in the atmosphere from past emissions. {2.1, 2.3, 3.1; Ch. 2, Introduction}

National and international commitments seek to limit global warming to well below 2°C (3.6°F), and preferably to 1.5°C (2.7°F), compared to preindustrial temperature conditions (defined as the 1850–1900 average). To achieve this, global CO₂ emissions would have to reach net zero by around 2050 (Figure 1.4); global emissions of all greenhouse gases would then have to reach net zero within the following few decades. {2.3, 32.1}

A time series graph illustrates observed and future global carbon dioxide (abbreviated CO2) emissions pathways, as described in the caption. Y-axis values range from negative 20 to positive 140 billion metric tons of CO2 emissions per year. A gray line shows observed emissions. Five colored lines show the emissions pathways associated with five Shared Socioeconomic Pathways (abbreviated SSP), which are labeled (from top to bottom) as: Very high (SSP5-8.5; brown line); high (SSP 3-7.0; red line); Intermediate (SSP2-4.; yellow line); low (SSP 1-2.6; dark blue line); and very low (SSP1-1.9; light blue line). A text box describes the five emissions pathways, noting that climate modeling experts develop global climate projections for a range of plausible futures and that the graph shows five potential global CO2 emissions pathways. Another text box notes that the horizontal line extending across at the 0 y-axis value indicates net-zero CO2 emissions, that net zero occurs when human-caused global CO2 emissions cross this zero line, and that where an emissions pathway falls below this line, more CO2 is being removed from the atmosphere than is being added. A vertical dashed gray line is labeled “today,” or 2023. Observed global emissions (solid gray line) rise from about 30 billion metric tons per year in 2000 to just over 40 billion in 2015. Emissions in the future scenarios rise from just over 40 billion metric tons per year in 2015 to about 130 billion in 2100 under the very high scenario and about 85 billion under the high scenario. Under the intermediate scenario, they increase slightly over the next two decades before declining to about 10 billion by 2100. Under the low scenario, emissions decline steadily to about negative 5 by 2100. Under the very low scenario, they decline more rapidly to about negative 15. The very low and low pathways cross below the net-zero threshold at around 2055 and 2075, respectively.

Different scenarios of future carbon dioxide emissions are used to explore the range of possible climate futures.

Figure 1.4. The five scenarios shown (colored lines) demonstrate potential global carbon dioxide (CO₂) emissions pathways modeled from 2015 through 2100, with the solid light gray line showing observed global CO₂ emissions from 2000 to 2015. See Table 3 in the Guide to the Report for scenario definitions. Many projected impacts described in this report are based on a potential climate future defined by one or more of these scenarios for future CO₂ emissions from human activities, the largest long-term driver of climate change. The vertical dashed line, labeled “Today,” marks the year 2023; the solid horizontal black line marks net-zero CO₂ emissions. Adapted with permission from Figure TS.4 in Arias et al. 2021.

While US greenhouse gas emissions are falling, the current rate of decline is not sufficient to meet national and international climate commitments and goals. US net greenhouse gas emissions remain substantial and would have to decline by more than 6% per year on average, reaching net-zero emissions around midcentury, to meet current national mitigation targets and international temperature goals; by comparison, US greenhouse gas emissions decreased by less than 1% per year on average between 2005 and 2019. {32.1}

Many cost-effective options that are feasible now have the potential to substantially reduce emissions over the next decade. Faster and more widespread deployment of renewable energy and other zero- and low-carbon energy options can accelerate the transition to a decarbonized economy and increase the chances of meeting a 2050 national net-zero greenhouse gas emissions target for the US. However, to reach the US net-zero emissions target, additional mitigation options need to be explored and advanced (see “Available mitigation strategies can deliver substantial emissions reductions, but additional options are needed to reach net zero” below). {5.3, 6.3, 32.2, 32.3}

Authors

Federal Coordinating Lead Author: Allison R. Crimmins, US Global Change Research Program
Chapter Lead Author: Alexa K. Jay, US Global Change Research Program / ICF
Chapter Authors: Christopher W. Avery, US Global Change Research Program / ICF; Travis A. Dahl, US Army Corps of Engineers; Rebecca S. Dodder, US Environmental Protection Agency; Benjamin D. Hamlington, NASA Jet Propulsion Laboratory; Allyza R. Lustig, US Global Change Research Program / ICF; Kate Marvel, Project Drawdown; Pablo A. Méndez-Lazaro, University of Puerto Rico; Mark S. Osler, National Oceanic and Atmospheric Administration; Adam Terando, US Geological Survey; Emily Weeks, US Agency for International Development; Ariela Zycherman, NOAA Climate Program Office

Contributors

Review Editor: Emily K. Laidlaw, Laidlaw Scientific
USGCRP Coordinator: Christopher W. Avery, US Global Change Research Program / ICF

About the Overview

The Fifth National Climate Assessment documents observed and projected vulnerabilities, risks, and impacts associated with climate change across the United States and provides examples of response actions underway in many communities. This Overview presents highlights from the Assessment, providing summary findings and a synthesis of material from the underlying chapters. Curly brackets indicate cross-references to full chapters (e.g., {Ch. 2}), Key Messages (e.g., {2.1}), figures (e.g., {Figure 32.8}), and other text elements.

Recommended Citation

Jay, A.K., A.R. Crimmins, C.W. Avery, T.A. Dahl, R.S. Dodder, B.D. Hamlington, A. Lustig, K. Marvel, P.A. Méndez-Lazaro, M.S. Osler, A. Terando, E.S. Weeks, and A. Zycherman, 2023: Ch. 1. Overview: Understanding risks, impacts, and responses. In: Fifth National Climate Assessment. Crimmins, A.R., C.W. Avery, D.R. Easterling, K.E. Kunkel, B.C. Stewart, and T.K. Maycock, Eds. U.S. Global Change Research Program, Washington, DC, USA. https://doi.org/10.7930/NCA5.2023.CH1

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How the United States Is Experiencing Climate Change

As extreme events and other climate hazards intensify, harmful impacts on people across the United States are increasing. Climate impacts—combined with other stressors—are leading to ripple effects across sectors and regions that multiply harms, with disproportionate effects on underserved and overburdened communities.

Current climate changes are unprecedented over thousands of years

Global greenhouse gas emissions from human activities continue to increase, resulting in rapid warming (Figure 1.5) and other large-scale changes, including rising sea levels, melting ice, ocean warming and acidification, changing rainfall patterns, and shifts in timing of seasonal events. Many of the climate conditions and impacts people are experiencing today are unprecedented for thousands of years (Figure 1.6). {2.1, 3.1; Figures A4.6, A4.7, A4.10, A4.13}

A time series graph shows US and global changes in average surface temperature for 1895 to 2022, as described in the caption. The y-axis shows temperature change in degrees Fahrenheit, with values ranging from negative 2 to positive 4. The line showing US temperatures uses color coding to note that different parts of the US are included in the data depending on time period. Light blue from 1895 to 1925 indicates data are for only the contiguous United States (abbreviated CONUS). From 1926 to 1950, teal indicates that the data include both CONUS and Alaska. From 1951 to 2022, teal indicates data are for all of the US. Global temperature is shown as a black line. Global temperature values are between 0 and negative 1 until about 1935, vary around zero through the early 1970s, and then increase steadily to more than 1.5 by around 2015. US temperatures show more year to year variability throughout, but generally follow the same trends as global temperatures. Exceptions are the 1930s, where the US shows higher temperatures, and most years since around 1995, where US temperatures are usually above the global average, with a peak of more than 3.5 around 2015.

The US has warmed rapidly since the 1970s.

Figure 1.5. The graph shows the change in US annual average surface temperature during 1895–2022 compared to the 1951–1980 average. The temperature trend changes color as data become available for more regions of the US, with Alaska data added to the average temperature for the contiguous US (CONUS) beginning in 1926 (medium blue line) and Hawaiʻi, Puerto Rico, and US-Affiliated Pacific Islands data added beginning in 1951 (dark blue line). Global average surface temperature is shown by the black line. Figure credit: NOAA NCEI and CISESS NC.

Current climate conditions are unprecedented for thousands of years.

Figure 1.6. Human activities since industrialization have led to increases in atmospheric greenhouse gas concentrations that are unprecedented in records spanning hundreds of thousands of years. These are examples of some of the large and rapid changes in the climate system that are occurring as the planet warms. (Greenhouse gas concentrations {2.1}; sea level rise {3.4}; global temperature {2.1}; drought {2.2, 3.5}). Figure credit: USGCRP and ICF.

As the world’s climate has shifted toward warmer conditions, the frequency and intensity of extreme cold events have declined over much of the US, while the frequency, intensity, and duration of extreme heat have increased. Across all regions of the US, people are experiencing warming temperatures and longer-lasting heatwaves. Over much of the country, nighttime temperatures and winter temperatures have warmed more rapidly than daytime and summer temperatures. Many other extremes, including heavy precipitation, drought, flooding, wildfire, and hurricanes, are becoming more frequent and/or severe, with a cascade of effects in every part of the country. {2.1, 2.2, 3.4, 4.1, 4.2, 7.1, 9.1; Ch. 2, Introduction; App. 4; Focus on Compound Events}

Risks from extreme events are increasing

One of the most direct ways that people experience climate change is through changes in extreme events. Harmful impacts from more frequent and severe extremes are increasing across the country—including increases in heat-related illnesses and death, costlier storm damages, longer droughts that reduce agricultural productivity and strain water systems, and larger, more severe wildfires that threaten homes and degrade air quality. {2.2, 4.2, 12.2, 14.2, 15.1, 19.2; Focus on Western Wildfires}

Extreme weather events cause direct economic losses through infrastructure damage, disruptions in labor and public services, and losses in property values. The number and cost of weather-related disasters have increased dramatically over the past four decades, in part due to the increasing frequency and intensity of extreme events and in part due to increases in assets at risk (through population growth, rising property values, and continued development in hazard-prone areas). Low-income communities, communities of color, and Tribes and Indigenous Peoples experience high exposure and vulnerability to extreme events due to both their proximity to hazard-prone areas and lack of adequate infrastructure or disaster management resources. {2.2, 4.2, 17.3, 19.1; Focus on Compound Events}

In the 1980s, the country experienced, on average, one (inflation-adjusted) billion-dollar disaster every four months. Now, there is one every three weeks, on average. Between 2018 and 2022, the US experienced 89 billion-dollar events (Figure 1.7). Extreme events cost the US close to $150 billion each year—a conservative estimate that does not account for loss of life, healthcare-related costs, or damages to ecosystem services. {2.2, 19.1; Ch. 2, Introduction; Figures 4.1, A4.5}

A map of the United States shows monetary damages from billion-dollar disasters by state from 2018 to 2022, as described in the caption. A legend shows amounts in billions of dollars, with values ranging from 1 or less (white) to 90 or more (dark red). Hawai’i and the US Virgin Islands show damages of 1 billion dollars or less. Areas showing damages of 1 to 5 billion are Alaska, Washington, Oregon, Idaho, Montana, Wyoming, Nevada, Utah, Arizona, New Mexico, North Dakota, Michigan, Indiana, Kentucky, Mississippi, Maine, Vermont, New Hampshire, Massachusetts, Rhode Island, Connecticut, Delaware, Maryland, West Virginia, Virginia, and Puerto Rico. States showing damages of 5 to 10 billion are Minnesota, Wisconsin, South Dakota, Kansas, Oklahoma, Illinois, Missouri, Arkansas, Tennessee, Alabama, South Carolina, Ohio, and Pennsylvania. Nebraska, New York, New Jersey, and Georgia show damages of 10 to 15 billion; Colorado and Iowa show damages of 15 to 30 billion; California, Texas, Louisiana, and North Carolina show damages of 30 to 90 billion; and Florida shows damages of 90 billion or more.

The US now experiences, on average, a billion-dollar weather or climate disaster every three weeks.

Figure 1.7. Billion-dollar weather and climate disasters are events where damages/costs reach or exceed $1 billion, including adjustments for inflation. Between 2018 and 2022, 89 such events affected the US, including 4 droughts, 6 floods, 52 severe storms, 18 tropical cyclones, 5 wildfires, and 4 winter storm events (see Figure A4.5 for the number of billion-dollar disasters per year). During this period, Florida had the highest total damages ($140 billion) and experienced the highest damages from a single event—Hurricane Ian ($113 billion). Over the 1980–2022 period, Texas had the highest total damages ($375 billion). While similar data are not available for the US-Affiliated Pacific Islands, Super Typhoon Yutu caused $500 million in property damage alone in Saipan and the northern Marianas in 2018 (NCEI 2019). Increasing costs over time are driven by changes in the assets at risk and the increase in frequency or intensity of extreme events caused by climate change. Adapted from NCEI 2023.

Cascading and compounding impacts increase risks

The impacts and risks of climate change unfold across interacting sectors and regions. For example, wildfire in one region can affect air quality and human health in other regions, depending on where winds transport smoke. Further, climate change impacts interact with other stressors, such as the COVID-19 pandemic, environmental degradation, or socioeconomic stressors like poverty and lack of adequate housing that disproportionately impact overburdened communities. These interactions and interdependencies can lead to cascading impacts and sudden failures. For example, climate-related shocks to the food supply chain have led to local to global impacts on food security and human migration patterns that affect US economic and national security interests. {11.3, 17.1, 17.2, 17.3, 18.1, 22.3, 23.4, 31.3; Introductions in Chs. 2, 17, 18; Focus on Compound Events; Focus on Risks to Supply Chains; Focus on COVID-19 and Climate Change}

The risk of two or more extreme events occurring simultaneously or in quick succession in the same region—known as compound events—is increasing. Climate change is also increasing the risk of multiple extremes occurring simultaneously in different locations that are connected by complex human and natural systems. For instance, simultaneous megafires across multiple western states and record back-to-back Atlantic hurricanes in 2020 caused unprecedented demand on federal emergency response resources. {2.2, 3.2, 15.1, 22.2, 26.4; Focus on Compound Events; Ch. 4, Introduction}

Compound events often have cascading impacts that cause greater harm than individual events. For example, in 2020, record-breaking heat and widespread drought contributed to concurrent destructive wildfires across California, Oregon, and Washington, exposing millions to health hazards and straining firefighting resources. Ongoing drought amplified the record-breaking Pacific Northwest heatwave of June 2021, which was made 2° to 4°F hotter by climate change. The heatwave led to more than 1,400 heat-related deaths, another severe wildfire season, mass die-offs of fishery species important to the region’s economy and Indigenous communities, and total damages exceeding $38.5 billion (in 2022 dollars). {27.3; Ch. 2, Introduction; Focus on Compound Events, Focus on Western Wildfires}

Climate change exacerbates inequities

Some communities are at higher risk of negative impacts from climate change due to social and economic inequities caused by ongoing systemic discrimination, exclusion, and under- or disinvestment. Many such communities are also already overburdened by the cumulative effects of adverse environmental, health, economic, or social conditions. Climate change worsens these long-standing inequities, contributing to persistent disparities in the resources needed to prepare for, respond to, and recover from climate impacts. {4.2, 9.2, 12.2, 14.3, 15.2, 16.1, 16.2, 18.2, 19.1, 20.1, 20.3, 21.3, 22.1, 23.1, 26.4, 27.1, 31.2}

For example, low-income communities and communities of color often lack access to adequate flood infrastructure, green spaces, safe housing, and other resources that help protect people from climate impacts. In some areas, patterns of urban growth have led to the displacement of under-resourced communities to suburban and rural areas with less access to climate-ready housing and infrastructure. Extreme heat can lead to higher rates of illness and death in low-income neighborhoods, which are hotter on average (Figure 1.8). Neighborhoods that are home to racial minorities and low-income people have the highest inland (riverine) flood exposures in the South, and Black communities nationwide are expected to bear a disproportionate share of future flood damages—both coastal and inland (Figure 1.9). {4.2, 11.3, 12.2, 15.1, 22.1, 22.2, 26.4, 27.1; Ch. 2, Introduction}

Three maps and three scatter plots show average maximum land surface temperature and its relationship to median household income for three cities. Panels (a), (b), and (c) show land surface temperatures in 2020 for, respectively, Atlanta, Houston, and Minneapolis. A legend shows temperature from a low of 63 degrees Fahrenheit (blue) to a high of 127 degrees (red). The Atlanta map shows values in the urban center in the range of 90 to 110 degrees, falling down to the 60s in the city’s periphery. Houston shows considerably higher values, with large areas in the 120s, again with cooler areas on the outer fringes of the map. Minneapolis is considerably cooler, with some values in the 100° range but far more areas in the 60° to 80° range, especially in western and northern parts of the city. Panels (d), (e), and (f) are scatterplots for, respectively, Atlanta, Houston, and Minneapolis, with median household income from $20,000 to $260,000 on the x-axis. Black dots show individual data points, and red lines show the estimated trend analysis. In Atlanta, the average maximum land surface temperature falls from over 100 degrees Fahrenheit for incomes of $20,000 to about 95 degrees for incomes of $260,000. In Houston, the average maximum land surface temperature falls from over 110 degrees for incomes of $20,000 to about 105 degrees for incomes of $260,000. In Minneapolis, the average maximum land surface temperature falls from about 104 degrees for incomes of $20,000 to about 85 degrees for incomes of $260,000.

Lower-income urban neighborhoods experience higher surface temperatures.

Figure 1.8. The figure shows the spatial distribution of maximum land surface temperature (LST) in 2020 for Atlanta (a), Houston (b), and Minneapolis (c). Graphs (d), (e), and (f) depict the relationship between maximum LST and median household income across census tracts in each city (see also Figure A4.4). A statistical trend analysis (the Theil-Sen estimator) returns negative values for all three cities, indicating that LST decreases as income increases (solid red line). Dashed red lines indicate the 95% confidence interval, meaning that the true slope of the trend is expected to fall within this range. Note that LST is measured at ground level and may differ from surface air temperature, which is measured at a height of 2 meters. {Figure 12.6} Portions of this figure include intellectual property of Esri and its licensors and are used under license. Copyright © 2020 Esri and its licensors. All rights reserved. Figure credit: University of California, Davis; University of Texas at El Paso; Massachusetts Institute of Technology; City of Phoenix, Arizona; and USGS.

These disproportionate impacts are partly due to exclusionary housing practices—both past and ongoing—that leave underserved communities with less access to heat and flood risk-reduction strategies and other economic, health, and social resources. For example, areas that were historically redlined—a practice in which lenders avoided providing services to communities, often based on their racial or ethnic makeup—continue to be deprived of equitable access to environmental amenities like urban green spaces that reduce exposure to climate impacts. These neighborhoods can be as much as 12°F hotter during a heatwave than nearby wealthier neighborhoods. {8.3, 9.2, 12.2, 15.2, 20.3, 21.3, 22.1, 26.4, 27.1, 32.4; Ch. 2, Introduction}

A bar chart shows projected increases in annual average losses (abbreviated A A L s) due to floods by 2050. The bars show projections based on percentage of Black residents in US census tracts. The y-axis show percent change in 2050 compared to 2020, with values ranging from 0 to 40 percent. A dashed gray line and text show that the national average increase is projected to be 26.4 percent. In general, the chart shows that the higher the percentage of Black residents, the higher the projected increase in A A L. In Census tracts where less than 1 percent of residents are Black, projected change in A A L is a little less than 20 percent. In tracts where 1 to 2 percent of residents are Black, the figure is slightly more than 20 percent. In tracts where 2 to 7 percent of residents are Black, the figure is slightly above the national average of 26.4 percent. In tracts where 7 to 20 percent of residents are Black, the figure is just above 30 percent. In tracts where more than 20 percent of residents are Black, the figure is about 40 percent.

Losses due to floods are projected to increase disproportionately in US Census tracts with higher percentages of Black residents.

Figure 1.9. The bars show that the average annual losses—or the economic damage in a typical year—due to floods in census tracts with a Black population of at least 20% are projected to increase at roughly twice the rate of that in tracts where Black populations make up less than 1% of population. {Figure 4.14} Adapted from Wing et al. 2022 [CC BY 4.0].

Harmful impacts will increase in the near term

Even if greenhouse gas emissions fall substantially, the impacts of climate change will continue to intensify over the next decade (see “Meeting US mitigation targets means reaching net-zero emissions” above; Box 1.4), and all US regions are already experiencing increasingly harmful impacts. Although a few US regions or sectors may experience limited or short-term benefits from climate change, adverse impacts already far outweigh any positive effects and will increasingly eclipse benefits with additional warming. {2.3, 19.1; Ch. 2, Introduction; Chs. 21–30}

Table 1.2 shows examples of critical impacts expected to affect people in each region between now and 2030, with disproportionate effects on overburdened communities. While these examples affect particular regions in the near term, impacts often cascade through social and ecological systems and across borders and may lead to longer-term losses. {15.2, 18.2, 20.1; Figure 15.5; Ch. 20, Introduction}

Table 1.2. Climate Change Is Already Affecting All US Regions and Will Continue to Have Impacts in the Near Term

The table shows three climate impacts of significant concern to each US region between now and 2030. Icons indicate general categories of impacts: infrastructure, water supply, health and well-being, food security, economy, livelihoods and heritage, and ecosystems. More information can be found in the regional chapters (Chs. 21–30) via the Key Message links shown in the table.

Category Key:

Infrastructure Water supply icon

Water Supply Health icon

Health and Well-being Food security icon

Food Security Economy icon

Economy

Livelihoods and Heritage Ecosystems icon

Ecosystems

Region	Example Impacts
Northeast	Extreme weather events damage critical infrastructure. {21.1}	Warming temperatures shift distributions of coastal and marine species and habitats. {21.2}	Extreme heat and flooding disproportionately impact overburdened communities. {21.3}
Southeast	Sea level rise and coastal flooding harm rapidly growing communities. {22.1}	Extreme heat threatens human health, especially stressing urban communities. {22.2}	Heavy rain and longer dry spells reduce water supply and access. {22.4}
US Caribbean	Agricultural losses, especially from tropical cyclones, threaten food security. {23.1}	Severe drought leads to large agricultural and economic losses. {23.3}	Rising temperatures increase mortality and power demand; hurricanes and storms stress power grids. {23.2, 23.4}
Midwest	Rising temperatures and extreme events threaten livelihoods and trades. {24.2}	Extreme weather events harm public health. {24.3}	Rising temperatures and extreme rainfall damage buildings, homes, and businesses. {24.4}
Northern Great Plains	Rising temperatures and decreasing snowpack reduce water supply. {25.1}	Increases in extreme heat, wildfire, and flooding harm physical and mental health. {25.1, 25.2}	Livelihoods are at greater risk, especially in agriculture, recreation, and energy sectors. {25.3}
Southern Great Plains	Drier conditions threaten agriculture, ecosystems, and water supplies. {26.1, 26.2, 26.5}	Extreme heat and high humidity harm human health and exacerbate inequities. {26.4}	Multiple stressors and extreme events disrupt business, outdoor recreation, and leisure activities. {26.1, 26.2, 26.3}
Northwest	Less water is available for hydropower, rural communities, and aquatic ecosystems. {27.1, 27.2, 27.4}	Extreme heat and wildfire smoke endanger at-risk urban, rural, and Tribal communities. {27.1, 27.3, 27.5}	Wildfire, extreme heat, and floods threaten livelihoods and heritage tied to natural resources. {27.1, 27.3, 27.6}
Southwest	Intensifying drought and decreases in groundwater recharge reduce water supply. {28.1}	Economic losses to farmers and ranchers increase. {28.3}	Extreme heat, drought, wildfire smoke, and coastal flooding harm physical and mental health. {28.3, 28.4}
Alaska	Landscape degradation increases damage to private and municipal infrastructure. {29.2, 29.4}	Reduced fish stocks harm local economies, Tribal sovereignty, and overall well-being. {29.6, 29.7}	Diminished access to mammals, seabirds, fish, and vegetation decreases local food security. {29.5}
Hawai‘i and US-Affiliated Pacific Islands	Sea level rise and saltwater intrusion reduce irrigation and drinking water supply. {30.1}	Damages to the coastal built environment, including traditional structures, increase. {30.3, 30.5}	Risks to unique and biodiverse flora and fauna continue to grow. {30.4}

Current and Future Climate Risks to the United States

Climate changes are making it harder to maintain safe homes and healthy families; reliable public services; a sustainable economy; thriving ecosystems, cultures, and traditions; and strong communities. Many of the extreme events and harmful impacts that people are already experiencing will worsen as warming increases and new risks emerge.

Safe, reliable water supplies are threatened by flooding, drought, and sea level rise

More frequent and intense heavy precipitation events are already evident, particularly in the Northeast and Midwest. Urban and agricultural environments are especially vulnerable to runoff and flooding. Between 1981 and 2016, US corn yield losses from flooding were comparable to those from extreme drought. Runoff and flooding also transport debris and contaminants that cause harmful algal blooms and pollute drinking water supplies. Communities of color and low-income communities face disproportionate flood risks. {2.2, 4.2, 6.1, 9.2, 21.3, 24.1, 24.5, 26.4; Figure A4.8}

Between 1980 and 2022, drought and related heatwaves caused approximately $328 billion in damages (in 2022 dollars). Recent droughts have strained surface water and groundwater supplies, reduced agricultural productivity, and lowered water levels in major reservoirs, threatening hydropower generation. As higher temperatures increase irrigation demand, increased pumping could endanger groundwater supplies, which are already declining in many major aquifers. {4.1, 4.2; Figure A4.9}

Droughts are projected to increase in intensity, duration, and frequency, especially in the Southwest, with implications for surface water and groundwater supplies. Human and natural systems are threatened by rapid shifts between wet and dry periods that make water resources difficult to predict and manage. {2.2, 2.3, 4.1, 4.2, 5.1, 28.1}

In coastal environments, dry conditions, sea level rise, and saltwater intrusion endanger groundwater aquifers and stress aquatic ecosystems. Inland, decreasing snowpack alters the volume and timing of streamflow and increases wildfire risk. Small rural water providers that often depend on a single water source or have limited capacity are especially vulnerable. {4.2, 7.2, 9.2, 21.2, 22.1, 23.1, 23.3, 25.1, 27.4, 28.1, 28.2, 28.5, 30.1; Figure A4.7}

Many options are available to protect water supplies, including reservoir optimization, nature-based solutions, and municipal management systems to conserve and reuse water. Collaboration on flood hazard management at regional scales is particularly important in areas where flood risk is increasing, as cooperation can provide solutions unavailable at local scales. {4.3, 9.3, 26.5; Focus on Blue Carbon}

(left; Toledo, Ohio) Rising temperatures are intensifying harmful algal blooms, negatively affecting human and animal health. (top right; Utah, Arizona) Water levels on Lake Powell have fallen to historic lows in recent years, affecting millions of people across the Southwest. (bottom right) Rain gardens, a form of green infrastructure, absorb excess stormwater. Photo credits: (left) Aerial Associates Photography Inc. by Zachary Haslick; (top right) NASA Earth Observatory images by Lauren Dauphin, using Landsat data from the USGS; (bottom right) Alisha Goldstein, EPA.

Disruptions to food systems are expected to increase

As the climate changes, increased instabilities in US and global food production and distribution systems are projected to make food less available and more expensive. These price increases and disruptions are expected to disproportionately affect the nutrition and health of women, children, older adults, and low-wealth communities. {11.2, 15.2}

Climate change also disproportionately harms the livelihoods and health of communities that depend on agriculture, fishing, and subsistence lifestyles, including Indigenous Peoples reliant on traditional food sources. Heat-related stress and death are significantly greater for farmworkers than for all US civilian workers. {11.2, 11.3, 15.1, 15.2, 16.1; Focus on Risks to Supply Chains}

While farmers, ranchers, and fishers have always faced unpredictable weather, climate change heightens risks in many ways:

Increasing temperatures, along with changes in precipitation, reduce productivity, yield, and nutritional content of many crops. These changes can introduce disease, disrupt pollination, and result in crop failure, outweighing potential benefits of longer growing seasons and increased CO₂ fertilization. {11.1, 19.1, 21.1, 22.4, 23.3, 24.1, 26.2}
Heavy rain and more frequent storms damage crops and property and contaminate water supplies. Longer-lasting droughts and larger wildfires reduce forage production and nutritional quality, diminish water supplies, and increase heat stress on livestock. {23.2, 25.3, 28.3}
Increasing water temperatures, invasive aquatic species, harmful algal blooms, and ocean acidification and deoxygenation put fisheries at risk. Fishery collapses can result in large economic losses, as well as loss of cultural identity and ways of life. {11.3, 29.3}

In response, some farmers and ranchers are adopting innovations—such as agroecological practices, data-driven precision agriculture, and carbon monitoring—to improve resilience, enhance soil carbon storage, and reduce emissions. Across the Nation, Indigenous food security efforts are helping improve community resilience to climate change while also improving cultural resilience. Some types of aquaculture have the potential to increase climate-smart protein production, human nutrition, and food security, although some communities have raised concerns over issues such as conflict with traditional livelihoods and the introduction of disease or pollution. {10.2, 11.1, 29.6, 25.5; Boxes 22.3, 27.2}

(left; Baltimore, Maryland) Urban farms offer the potential to reduce carbon emissions while helping to improve community food security. (top right; California) A Northern California vineyard is affected by wildfire. (bottom right; Kenai River, Alaska) Recent climate extremes have contributed to declines in many salmon populations. Photo credits: (left) Preston Keres, USDA/FPAC; (top right) Ordinary Mario/iStock via Getty Images; (bottom right) Eric Vance, EPA.

Homes and property are at risk from sea level rise and more intense extreme events

Homes, property, and critical infrastructure are increasingly exposed to more frequent and intense extreme events, increasing the cost of maintaining a safe and healthy place to live. Development in fire-prone areas and increases in area burned by wildfires have heightened risks of loss of life and property damage in many areas across the US. Coastal communities across the country—home to 123 million people (40% of the total US population)—are exposed to sea level rise (Figure 1.10), with millions of people at risk of being displaced from their homes by the end of the century. {2.3, 9.1, 12.2, 22.1, 27.4, 30.3; Figures A4.10, A4.14; Focus on Western Wildfires}

People who regularly struggle to afford energy bills—such as rural, low-income, and older fixed-income households and communities of color—are especially vulnerable to more intense extreme heat events and associated health risks, particularly if they live in homes with poor insulation and inefficient cooling systems. For example, Black Americans are more likely to live in older, less energy efficient homes and face disproportionate heat-related health risks. {5.2, 15.2, 15.3, 22.2, 26.4, 32.4; Figure A4.4}

Accessible public cooling centers can help protect people who lack adequate air-conditioning on hot days. Strategic land-use planning in cities, urban greenery, climate-smart building codes, and early warning communication can also help neighborhoods adapt. However, other options at the household scale, such as hardening homes against weather extremes or relocation, may be out of reach for renters and low-income households without assistance. {12.3, 15.3, 19.3, 22.2}

Box 1.2. Migration and Displacement

Extreme events, such as extended drought, wildfire, and major hurricanes, have contributed to human migration and displacement. For example, numerous extreme events over the last two decades drove migration of vulnerable communities in Puerto Rico and the US Virgin Islands to the mainland. {9.2, 15.1, 17.2, 19.2, 23.1, 23.5; Box 18.2}

In the future, the combination of climate change and other factors, such as housing affordability, is expected to increasingly affect migration patterns. More severe wildfires in California, increasing sea level rise in Florida, and more frequent flooding in Texas are expected to displace millions of people. Climate-driven economic changes abroad, including reductions in crop yields, are expected to increase the rate of emigration to the United States. {9.2, 17.2, 19.2, 30.3}

From Alaska to low-lying Pacific atolls, forced migrations and displacements driven by climate change disrupt social networks, decrease housing security, and exacerbate grief, anxiety, and negative mental health outcomes. Indigenous Peoples, who have long faced land dispossession due to settler colonialism, are again being confronted with displacement and loss of traditional resources and practices. {4.2, 15.1, 16.1, 19.1, 20.1, 20.3, 22.1, 22.2, 29.1, 30.3; Box 18.2}

Four maps show US flooding risks in 2020 and 2050. The two top maps, which depict all of North America and much of the Pacific ocean, show the number of observed minor high tide flooding events per year in 2020 on the left and the projected number of such events per year in 2050 on the right. Legend values range from 0.02 or fewer events per year (light yellow) to 10 or more (dark blue). For 2020, values along the Atlantic and Gulf coasts are generally in the 1 to 5 or 5 to 10 range, with values of 0.1. to 0.2 in Florida and lower values for the US Caribbean. Values on the Pacific coast are generally in the 1 to 5 range, with a few locations showing lower values and several locations in the Northwest showing higher values. Values in Alaska range from 0.02 or fewer events to 10 or more. Values in Hawaii and the US-Affiliated Pacific Islands are generally 0.05 to 0.1 or 0.1 to 0.2. In 2050, increases are shown virtually everywhere, with almost all locations on the Atlantic, Pacific, and Gulf coasts, as well as the US Caribbean and Hawaii and US-Affiliated islands, showing 10 or more events per year, except for a few in the 1 to 5 or 5 to 10 range. Many areas in Alaska also show increases to the 0.2 to 1 range. The two bottom maps are for the contiguous US only and show the annual average losses from all types of flooding by county. The left map shows losses in millions of 2020 dollars for 2020, with values ranging from 1 million or less (light red) to 20 million or more (dark red). The right map shows the percent change between 2020 and 2050, with values ranging from zero percent or less (very light green) to increases of 20 percent or more (dark green). Losses in 2020 are generally in the 20 million or more range for urban areas in the Northeast, along the Appalchian mountains in the Northeast and Southeast, along the Florida coast and much of the Gulf Coast, and in widespread areas of the Northwest and Southwest. Several locations in the Midwest and a few locations in the Southern Great Plains and in Montana also show losses of 20 million or more. Most other counties show losses of 1 million or less or 1 to 10 million. Areas with heavy losses in 2020 also tend to show the largest increases in losses for 2050, generally in the 10 to 20 percent or 20 percent or more ranges. However, many counties in the Midwest, Northern and Southern Great Plains, and Southwest do show decreases

Increasing flooding puts more people and assets at risk.

Figure 1.10. (top row) Maps show (a) the average number of minor high tide flooding events per year in 2020 (with historical sea level rise) and (b) the expected number of events per year in 2050 (when driven by extrapolated sea level rise). (bottom row) Maps show (c) average annual loss (AAL) from all types of flooding in millions of dollars in 2020 and (d) the projected changes in AAL in 2050 relative to 2020. AAL estimates were made only for the contiguous US. Over the next three decades, the number of flooding days along all coastlines of the US is expected to increase. These increases in the occurrence of flooding will drive greater AALs, especially in coastal areas of the US. (a, b) Adapted from Sweet et al. 2022; (c, d) adapted from Wing et al. 2022 [CC BY 4.0].

(left; Cedar Rapids, Iowa) More frequent and intense heavy precipitation events are already evident, particularly in the Northeast and Midwest. (right; Arizona) The 2021 Telegraph Fire destroyed homes and property. Photo credits: (left) Don Becker, USGS; (right) Andrew Avitt, USDA Forest Service.

Infrastructure and services are increasingly damaged and disrupted by extreme weather and sea level rise

Climate change threatens vital infrastructure that moves people and goods, powers homes and businesses, and delivers public services. Many infrastructure systems across the country are at the end of their intended useful life and are not designed to cope with additional stress from climate change. For example, extreme heat causes railways to buckle, severe storms overload drainage systems, and wildfires result in roadway obstruction and debris flows. Risks to energy, water, healthcare, transportation, telecommunications, and waste management systems will continue to rise with further climate change, with many infrastructure systems at risk of failing. {12.2, 13.1, 15.2, 23.4, 26.5; Focus on Risks to Supply Chains}

In coastal areas, sea level rise threatens permanent inundation of infrastructure, including roadways, railways, ports, tunnels, and bridges; water treatment facilities and power plants; and hospitals, schools, and military bases. More intense storms also disrupt critical services like access to medical care, as seen after Hurricanes Irma and Maria in the US Virgin Islands and Puerto Rico. {9.2, 23.1, 28.2, 30.3}

At the same time, climate change is expected to place multiple demands on infrastructure and public services. For example, higher temperatures and other effects of climate change, such as greater exposure to stormwater or wastewater, will increase demand for healthcare. Continued increases in average temperatures and more intense heatwaves will heighten electricity and water demand, while wetter storms and intensified hurricanes will strain wastewater and stormwater management systems. In the Midwest and other regions, aging energy grids are expected to be strained by disruptions and transmission efficiency losses from climate change. {23.4, 24.4, 30.2}

Forward-looking designs of infrastructure and services can help build resilience to climate change, offset costs from future damage to transportation and electrical systems, and provide other benefits, including meeting evolving standards to protect public health, safety, and welfare. Mitigation and adaptation activities are advancing from planning stages to deployment in many areas, including improved grid design and workforce training for electrification, building upgrades, and land-use choices. Grid managers are gaining experience planning and operating electricity systems with growing shares of renewable generation and working toward understanding the best approaches for dealing with the natural variability of wind and solar sources alongside increases in electrification. {5.3, 12.3, 13.1, 13.2, 22.3, 24.4, 32.3; Figure 22.17}

(left; Oregon) The Hooskanaden Landslide, triggered by heavy rainfall, caused substantial road damage. (right; Maunabo, Puerto Rico) Punta Tuna Wetlands Nature Reserve, which helps buffer the coastline from extreme events, was severely damaged during Hurricane Maria in 2017. Photo credits: (left) Oregon Department of Transportation [CC BY 2.0]; (right) Kenneth Wilsey, FEMA.

Climate change exacerbates existing health challenges and creates new ones

Climate change is already harming human health across the US, and impacts are expected to worsen with continued warming. Climate change harms individuals and communities by exposing them to a range of compounding health hazards, including the following:

More severe and frequent extreme events {2.2, 2.3, 15.1}
Wider distribution of infectious and vector-borne pathogens {15.1, 26.1; Figure A4.16}
Air quality worsened by smog, wildfire smoke, dust, and increased pollen {14.1, 14.2, 14.4, 23.1, 26.1}
Threats to food and water security {11.2, 15.1}
Mental and spiritual health stressors {15.1}

While climate change can harm everyone’s health, its impacts exacerbate long-standing disparities that result in inequitable health outcomes for historically marginalized people, including people of color, Indigenous Peoples, low-income communities, and sexual and gender minorities, as well as older adults, people with disabilities or chronic diseases, outdoor workers, and children. {14.3, 15.2}

The disproportionate health impacts of climate change compound with similar disparities in other health contexts. For example, climate-related disasters during the COVID-19 pandemic, such as drought along the Colorado River basin, western wildfires, and Hurricane Laura, disproportionately magnified COVID-19 exposure, transmission, and disease severity and contributed to worsened health conditions for essential workers, older adults, farmworkers, low-wealth communities, and communities of color. {15.2; Focus on COVID-19 and Climate Change}

Large reductions in greenhouse gas emissions are expected to result in widespread health benefits and avoided death or illness that far outweigh the costs of mitigation actions. Improving early warning, surveillance, and communication of health threats; strengthening the resilience of healthcare systems; and supporting community-driven adaptation strategies can reduce inequities in the resources and capabilities needed to adapt as health threats from climate change continue to grow. {14.5, 15.3, 26.1, 30.2, 32.4}

(left; New York, New York) The Empire State Building is shrouded in a haze caused by smoke from the 2023 Canadian wildfires. (top right; Conway, South Carolina) An ambulance drives through floodwaters. (bottom right; Atlanta, Georgia) Heatwaves in the Southeast are happening more frequently. Park amenities, such as trees and splash pads, help cool people on hot days. Photo credits: (left) Anthony Quintano [CC BY 2.0]; (top right) US Air National Guard photo by Tech. Sgt. Jorge Intriago; (bottom right) ucumari photography [CC BY-NC-ND 2.0].

Box 1.3. Indigenous Ways of Life and Spiritual Health

Indigenous communities, whose ways of life, cultures, intergenerational continuity, and spiritual health are tied to nature and the environment, are experiencing disproportionate health impacts of climate change. Rising temperatures and intensifying extreme events are reducing biodiversity and shifting the ranges of culturally important species like Pacific salmon, wild rice, and moose, making it more difficult for Indigenous Peoples to fish, hunt, and gather traditional and subsistence resources within Tribal jurisdictions. Heatwaves can prevent Tribal members from participating in traditional ceremonies, while flooding, erosion, landslides, and wildfires increasingly disrupt or damage burial grounds and ceremonial sites. {16.1, 15.2, 27.6}

Indigenous Peoples are leading numerous actions in response to climate change, including planning and policy initiatives, youth movements, cross-community collaborative efforts, and the expansion of renewable energy (Figure 1.11). Many of these efforts involve planning processes that start with place-based Indigenous Knowledge of local climate and ecosystems. {16.3}

Figure 1.11. For over 2,000 years, the Hopi People have farmed on land with only 6–10 inches of annual precipitation. Today, Hopi children learn both the practices and process of Hopi dryland farming and the values, customs, and identities that underpin them. Photo credit: ©Michael K. Johnson. {Panel from Figure 16.6}

Ecosystems are undergoing transformational changes

Together with other stressors, climate change is harming the health and resilience of ecosystems, leading to reductions in biodiversity and ecosystem services. Increasing temperatures continue to shift habitat ranges as species expand into new regions or disappear from unfavorable areas, altering where people can hunt, catch, or gather economically important and traditional food sources. Degradation and extinction of local flora and fauna in vulnerable ecosystems like coral reefs and montane rainforests are expected in the near term, especially where climate changes favor invasive species or increase susceptibility to pests and pathogens. Without significant emissions reductions, rapid shifts in environmental conditions are expected to lead to irreversible ecological transformations by mid- to late century. {2.3, 6.2, 7.1, 7.2, 8.1, 8.2, 10.1, 10.2, 21.1, 24.2, 27.2, 28.5, 29.3, 29.5, 30.4; Figure A4.12}

Changes in ocean conditions and extreme events are already transforming coastal, aquatic, and marine ecosystems. Coral reefs are being lost due to warming and ocean acidification, harming important fisheries; coastal forests are converting to ghost forests, shrublands, and marsh due to sea level rise, reducing coastal protection; lake and stream habitats are being degraded by warming, heavy rainfall, and invasive species, leading to declines in economically important species. {8.1, 10.1, 21.2, 23.2, 24.2, 27.2; Figures 8.7, A4.11}

Increased risks to ecosystems are expected with further climate change and other environmental changes, such as habitat fragmentation, pollution, and overfishing. For example, mass fish die-offs from extreme summertime heat are projected to double by midcentury in northern temperate lakes under a very high scenario (RCP8.5). Continued climate changes are projected to exacerbate runoff and erosion, promote harmful algal blooms, and expand the range of invasive species. {4.2, 7.1, 8.2, 10.1, 21.2, 23.2, 24.2, 27.2, 28.2, 30.4}

While adaptation options to protect fragile ecosystems may be limited, particularly under higher levels of warming, management and restoration measures can reduce stress on ecological systems and build resilience. These measures include migration assistance for vulnerable species and protection of essential habitats, such as establishing wildlife corridors or places where species can avoid heat. Opportunities for nature-based solutions that assist in mitigation exist across the US, particularly those focused on protecting existing carbon sinks and increasing carbon storage by natural ecosystems. {8.3, 10.3, 23.2, 27.2; Focus on Blue Carbon}

(top left; Nags Head Woods, North Carolina) Coastal ghost forests result when trees are killed by sea level rise and saltwater intrusion. (top right; Molokai Island, Hawaiʻi) High island ecosystems are at risk due to invasive species, habitat destruction, intensifying fire, and drought. (bottom; Florida) A diver works on coral reef restoration around Florida Keys National Marine Sanctuary. Photo credits: (top left) NC Wetlands [NC BY 2.0]; (top right) Lucas Fortini, USGS; (bottom) Mitchell Tartt, NOAA.

Climate change slows economic growth, while climate action presents opportunities

With every additional increment of global warming, costly damages are expected to accelerate. For example, 2°F of warming is projected to cause more than twice the economic harm induced by 1°F of warming. Damages from additional warming pose significant risks to the US economy at multiple scales and can compound to dampen economic growth. {19.1}

International impacts can disrupt trade, amplify costs along global supply chains, and affect domestic markets. {17.3, 19.2; Focus on Risks to Supply Chains}
While some economic impacts of climate change are already being felt across the country, the impacts of future changes are projected to be more significant and apparent across the US economy. {19.1}
States, cities, and municipalities confront climate-driven pressures on public budgets and borrowing costs amid spending increases on healthcare and disaster relief. {19.2}
Household consumers face higher costs for goods and services, like groceries and health insurance premiums, as prices change to reflect both current and projected climate-related damages. {19.2}

Mitigation and adaptation actions present economic opportunities. Public and private measures—such as climate financial risk disclosures, carbon offset credit markets, and investments in green bonds—can avoid economic losses and improve property values, resilience, and equity. However, climate responses are not without risk. As innovation and trade open further investment opportunities in renewable energy and the country continues to transition away from fossil fuels, loss and disposal costs of stranded capital assets such as coal mines, oil and gas wells, and outdated power plants are expected. Climate solutions designed without input from affected communities can also result in increased vulnerability and cost burden. {17.3, 19.2, 19.3, 20.2, 20.3, 27.1, 31.6}

Many regional economies and livelihoods are threatened by damages to natural resources and intensifying extremes

Climate change is projected to reduce US economic output and labor productivity across many sectors, with effects differing based on local climate and the industries unique to each region. Climate-driven damages to local economies especially disrupt heritage industries (e.g., fishing traditions, trades passed down over generations, and cultural heritage–based tourism) and communities whose livelihoods depend on natural resources. {11.3, 19.1, 19.3}

As fish stocks in the Northeast move northward and to deeper waters in response to rapidly rising ocean temperatures, important fisheries like scallops, shrimp, and cod are at risk. In Alaska, climate change has already played a role in 18 major fishery disasters that were especially damaging for coastal Indigenous Peoples, subsistence fishers, and rural communities. {10.2, 21.2, 29.3}
While the Southeast and US Caribbean face high costs from projected labor losses and heat health risks to outdoor workers, small businesses are already confronting higher costs of goods and services and potential closures as they struggle to recover from the effects of compounding extreme weather events. {22.3, 23.1}
Agricultural losses in the Midwest, including lower corn yields and damages to specialty crops like apples, are linked to rapid shifts between wet and dry conditions and stresses from climate-induced increases in pests and pathogens. Extreme heat and more intense wildfire and drought in the Southwest are already threatening agricultural worker health, reducing cattle production, and damaging wineries. {24.1, 28.5}
In the Northern Great Plains, agriculture and recreation are expected to see primarily negative effects related to changing temperature and rainfall patterns. By 2070, the Southern Great Plains is expected to lose cropland acreage as lands transition to pasture or grassland. {25.3, 26.2}
Outdoor-dependent industries, such as tourism in Hawai‘i and the US-Affiliated Pacific Islands and skiing in the Northwest, face significant economic loss from projected rises in park closures and reductions in workforce as continued warming leads to deterioration of coastal ecosystems and shorter winter seasons with less snowfall. {7.2, 8.3, 10.1, 10.3, 19.1, 27.3, 30.4}

Mitigation and adaptation actions taken by businesses and industries promote resilience and offer long-term benefits to employers, employees, and surrounding communities. For example, as commercial fisheries adapt, diversifying harvest and livelihoods can help stabilize income or buffer risk. In addition, regulators and investors are increasingly requiring businesses to disclose climate risks and management strategies. {10.2, 19.3, 26.2}

(top left; Fort Myers Beach, Florida) Shops and restaurants were severely damaged or completed destroyed by Hurricane Ian in 2022. (bottom left; Whatcom County, Washington) Snow-based recreational industries, such as skiing in the Pacific Northwest, are projected to lose revenue due to declining snowpack. (right; Maine) A causeway connecting Little Deer Isle to Deer Isle (the largest lobster port in the state) is threatened by sea level rise. Photo credits: (top left) Coast Guard Petty Officer 3rd Class Gabriel Wisdom; (bottom left) US Forest Service–Pacific Northwest Region; (right) ©Jack Sullivan, Island Institute.

Job opportunities are shifting due to climate change and climate action

Many US households are already feeling the economic impacts of climate change. Climate change is projected to impose a variety of new or higher costs on most households as healthcare, food, insurance, building, and repair costs become more expensive. Compounding climate stressors can increase segregation, income inequality, and reliance on social safety net programs. Quality of life is also threatened by climate change in ways that can be more difficult to quantify, such as increased crime and domestic violence, harm to mental health, reduced happiness, and fewer opportunities for outdoor recreation and play. {11.3, 19.1, 19.3}

Climate change, and how the country responds, is expected to alter demand for workers and shift where jobs are available. For example, energy-related livelihoods in the Northern and Southern Great Plains are expected to shift as the energy sector transforms toward more renewables, low-carbon technologies, and electrification of more sectors of the economy. Losses in fossil fuel–related jobs are projected to be completely offset by greater increases in mitigation-related jobs, as increased demand for renewable energy and low-carbon technologies is expected to lead to long-term expansion in most states’ energy and decarbonization workforce (Figure 1.12). Grid expansion and energy efficiency efforts are already creating new jobs in places like Nevada, Vermont, and Alaska, and advancements in biofuels and agrivoltaics (combined renewable energy and agriculture) provide economic opportunities in rural communities. {10.2, 11.3, 19.3, 25.3, 26.2, 29.3, 32.4}

Additional opportunities include jobs in ecosystem restoration and construction of energy-efficient and climate-resilient housing and infrastructure. Workforce training and equitable access to clean energy jobs, which have tended to exclude women and people of color, are essential elements of a just transition to a decarbonized economy. {5.3, 19.3, 20.3, 22.3, 25.3, 26.2, 27.3, 32.4}

Three stacked bar and line graphs show energy employment for 2020 through 2050 under three alternative zet-zero pathways. The y axis shows net employment, ranging from a decrease of 1 million jobs below the zero axis to an increase of 7 million jobs above the zero axis. Shaded bar segments show the annual jobs gains or losses for 9 sectors: wind, solar, nuclear, grid, carbon dioxide (abbreviated C O 2), biomass, coal, natural gas, and oil. Black lines show the net change in jobs. Under a high electrification scenario (left chart), net jobs increase from 0 to about 2.8 million by 2050. The largest increases are from the grid sector, which accounts for nearly 1.5 jobs by 2050, as well as wind and solar at around 0.5 million each. Biomass jobs also show a small increase. Losses of about 0.5 million by 2050 are in the natural gas and oil sectors. A 100 percent renewable pathway shows slightly larger job losses of about 0.8 million total for natural gas and oil, but much larger increases in grid, wind, and solar, resulting in about 6 million new jobs for a net increase of more than 5 million jobs. For a renewable constrained pathway, job losses are smaller at less than 0.5 million, but job increases are also much smaller at about 1.1 million, resulting in a net gain of about 0.5 million. In this scenario, increases are mainly in the grid and nuclear sectors, with smaller increases in wind, solar, and biomass.

Employment gains in electrification and renewable energy industries are projected to far outpace job losses in fossil fuel industries.

Figure 1.12. Despite decreases in the number of fossil fuel–related jobs, the overall number of energy jobs (specifically those involved in the supply of energy) relative to 2019 is generally projected to increase in net-zero-emissions energy scenarios between 2020 and 2050, although by much more in some scenarios than in others. {Figure 32.17} Adapted with permission from Jenkins et al. 2021.

(top; Golden, Colorado) Solar panels are pictured on the campus of the National Renewable Energy Laboratory. (bottom left; San Antonio, Texas) Participants in the 2022 Collegiate Wind Competition focus on offshore wind projects. (bottom right; Lexington, Virginia) Workers install fiber-optic cables. Rural broadband deployment is associated with higher incomes and lower unemployment rates. Photo credits: (top and bottom left) Werner Slocum/NREL [CC-BY-NC-ND 2.0]; (bottom right) Preston Keres, USDA.

Climate change is disrupting cultures, heritages, and traditions

As climate change transforms US landscapes and ecosystems, many deeply rooted community ties, pastimes, Traditional Knowledges, and cultural or spiritual connections to place are at risk. Cultural heritage—including buildings, monuments, livelihoods, and practices—is threatened by impacts on natural ecosystems and the built environment. Damages to archaeological, cultural, and historical sites further reduce opportunities to transfer important knowledge and identity to future generations. {6.1, 7.2, 8.3, 9.2, 10.1, 12.2, 16.1, 22.1, 23.1, 26.1, 27.6, 28.2; Introductions in Chs. 10, 30}

Many outdoor activities and traditions are already being affected by climate change, with overall impacts projected to further hinder recreation, cultural practices, and the ability of communities to maintain local heritage and a sense of place. {19.1}

For example:

The prevalence of invasive species and harmful algal blooms is increasing as waters warm, threatening activities like swimming along Southeast beaches, boating and fishing for walleye in the Great Lakes, and viewing whooping cranes along the Gulf Coast. In the Northwest, water-based recreation demand is expected to increase in spring and summer months, but reduced water quality and harmful algal blooms are expected to restrict these opportunities. {24.2, 24.5, 26.3, 27.6}
Ranges of culturally important species are shifting as temperatures warm, making them harder to find in areas where Indigenous Peoples have access (see Box 1.3). {11.2, 24.2, 26.1}
Hikers, campers, athletes, and spectators face increasing threats from more severe heatwaves, wildfires, and floods and greater exposure to infectious disease. {22.2, 15.1, 26.3, 27.6}

Nature-based solutions and ecosystem restoration can preserve cultural heritage while also providing valuable local benefits, such as flood protection and new recreational opportunities. Cultural heritage can also play a key role in climate solutions, as incorporating local values, Indigenous Knowledge, and equity into design and planning can help reaffirm a community’s connection to place, strengthen social networks, and build new traditions. {7.3, 26.1, 26.3, 30.5}

(top left; Glacier National Park, Montana) Wildfire smoke jeopardizes participation in outdoor sports and recreation. (top right; Boston Harbor, Massachusetts) Sea level rise threatens historical and archaeological sites on the Boston Harbor Islands. (bottom; Goose Island, Texas) Whooping cranes, which draw birdwatchers to the Gulf of Mexico, are at risk due to flooding, drought, and upstream water use. Photo credit: (top left) Andrew Parlette [CC BY 2.0]; (top right) cmh2315fl [CC BY-NC 2.0]; (bottom) Alan Schmierer [CC0 1.0].

The Choices That Will Determine the Future

With each additional increment of warming, the consequences of climate change increase. The faster and further the world cuts greenhouse gas emissions, the more future warming will be avoided, increasing the chances of limiting or avoiding harmful impacts to current and future generations.

Societal choices drive greenhouse gas emissions

The choices people make on a day-to-day basis—how to power homes and businesses, get around, and produce and use food and other goods—collectively determine the amount of greenhouse gases emitted. Human use of fossil fuels for transportation and energy generation, along with activities like manufacturing and agriculture, has increased atmospheric levels of carbon dioxide (CO₂) and other heat-trapping greenhouse gases. Since 1850, CO₂ concentrations have increased by almost 50%, methane by more than 156%, and nitrous oxide by 23%, resulting in long-term global warming. {2.1, 3.1; Ch. 2, Introduction}

The CO₂ not removed from the atmosphere by natural sinks lingers for thousands of years. This means that CO₂ emitted long ago continues to contribute to climate change today. Because of historical trends, cumulative CO₂ emissions from fossil fuels and industry in the US are higher than from any other country. To understand the total contributions of past actions to observed climate change, additional warming from CO₂ emissions from land use, land-use change, and forestry, as well as emissions of nitrous oxide and the shorter-lived greenhouse gas methane, should also be taken into account. Accounting for all of these factors and emissions from 1850–2021, emissions from the US are estimated to comprise approximately 17% of current global warming. {2.1}

Carbon dioxide, along with other greenhouse gases like methane and nitrous oxide, is well-mixed in the atmosphere. This means these gases warm the planet regardless of where they were emitted. For the first half of the 20th century, the vast majority of greenhouse gas emissions came from the US and Europe. But as US and European emissions have been falling (US emissions in 2021 were 17% lower than 2005 levels), emissions from the rest of the world, particularly Asia, have been rising rapidly. The choices the US and other countries make now will determine the trajectory of climate change and associated impacts for many generations to come (Figure 1.13). {2.1, 2.3; Ch. 32}

Box 1.4. Global Warming Levels

Because long-term societal actions are uncertain, climate modeling experts use different scenarios of plausible futures to represent a range of possible trajectories. These scenarios capture variables such as the relationship between human behavior, greenhouse gas emissions, Earth’s responses to changes in the concentration of greenhouse gases in our atmosphere and ocean, and the resulting impacts, including temperature change and sea level rise. {3.3; Guide to the Report; App. 3}

Since there are uncertainties inherent in all of these factors—especially human behavior and the choices that determine emissions levels—the resulting range of projections are not predictions but instead reflect multiple potential future pathways. Future climate change under a given scenario is often expressed in one of two ways: as a range of potential outcomes in a future year (Figure 1.13a) or the time at which a specific outcome is expected (Figure 1.13b). {2.3, 3.3; App. 3}

Over the next decade, projected global warming is very similar across all scenarios. Updating energy infrastructure or making systemic economic and political changes takes time, thus temperature trajectories under different scenarios take time to diverge. {2.3}

By midcentury (2040–2070), differences between projected temperatures under higher and lower scenarios become apparent. By the end of the century, the global warming level—that is, how much the global average surface temperature increases above preindustrial levels—is expected to exceed 5.4°F (3°C) under high and very high scenarios (SSP3-7.0 and SSP5-8.5, respectively), and the world could see more than 7.2°F (4°C) of warming under a very high scenario (SSP5-8.5). Long-term global warming is expected to stay below 3.6°F (2°C) under a low scenario (SSP1-2.6) and can be limited to 2.7°F (1.5°C) only under a very low scenario (SSP1-1.9). {2.3}

The risk of exceeding a particular global warming level depends on future emissions. This means that projections are conditional: when or if the world reaches a particular level of warming is largely dependent on human choices. {2.3}

A time series chart and horizontal bar chart show potential warming pathways in the United States. The time series chart at top shows temperature warming in degrees Fahrenheit, ranging from 0 to 14 degrees, for 1975 through 2095. A dashed vertical line labeled “Today” indicates 2023. Text notes that future warming in the United States will depend on the total amount of global greenhouse gas emissions. A black line shows the five-year running average of observed US temperature. Temperatures show variability but have generally increased, and the five-year average is more than 2 degrees warmer in 2022 than in 1975. Colored lines show simulated historical and projected temperature change for the following five scenarios: very high (SSP5-8.5, dark red line), high (SSP3-7.0, red), intermediate (SSP2-4.5, yellow), low (SSP1-2.6, dark blue), and very low (SSP1-1.9, light blue). All scenarios show similar temperature change of 4 to 5 degrees by around 2035 but begin to diverge notably after that. Warming by 2095 ranges from more than 13 degrees under the very high scenario to about 8 degrees under the intermediate scenario. For the low scenario, warming levels off at about 5.5 degrees around 2065. For the very low scenario, warming peaks at around 4 degrees around 2040 before declining slightly. The bart chart at the bottom has text labeled Crossing Times that notes that whether—and when—a given temperature threshold is crossed depends on both the amount and rate of global greenhouse gas emissions. Bars are shown for the five scenarios on an x-axis ranging from about 2023 to 2095. Eleven color shades are used to indicate when warming thresholds ranging from 3 degrees to 13 degrees are reached under each scenario. Higher thresholds are reached, and more quickly, for the higher scenarios, with the very high scenario reaching 13 degrees before 2090. The low scenario reaches a maximum of about 5 degrees before 2050, while the very low scenario reaches 4 degrees between about 2030 and 2070 before dropping back to the 3 degree threshold.

When or if the US reaches a particular level of warming depends on global greenhouse gas emissions from human activities.

Figure 1.13. How much warming the US will experience—and when a given temperature threshold is crossed—depends on future global emissions. The top graph shows observed change in US surface temperature during 1975–2022 (black line, 5-year averaged) and modeled historical (1975–2014) and projected (2015–2095) change in surface temperature compared to 1951–1980, annually averaged over all 50 states and Puerto Rico under different climate scenarios (multicolored lines; see Table 3 in the Guide to the Report). The bottom graph shows the same projections in a different way, highlighting the year in which the US crosses temperature thresholds under each scenario. The vertical dashed line represents the year 2023. Data for the US-Affiliated Pacific Islands and the US Virgin Islands are not available. See Figure 1.5 for observed US and global temperature changes since 1895. Adapted with permission from Figure TS.1 in Arias et al. 2021.

Rising global emissions are driving global warming, with faster warming in the US

The observed global warming of about 2°F (1.1°C) over the industrial era is unequivocally caused by greenhouse gas emissions from human activities, with only very small effects from natural sources. About three-quarters of total emissions and warming (1.7°F [0.95°C]) have occurred since 1970. Warming would have been even greater without the land and ocean carbon sinks, which have absorbed more than half of the CO₂ emitted by humans. {2.1, 3.1, 7.2; Ch. 2, Introduction; Figures 3.1, 3.8}

The US is warming faster than the global average, reflecting a broader global pattern: land areas are warming faster than the ocean, and higher latitudes are warming faster than lower latitudes. Additional global warming is expected to lead to even greater warming in some US regions, particularly Alaska (Figure 1.14). {2.1, 3.4; Ch. 2, Introduction; App. 4}

Maps of the contiguous United States, Alaska, Hawaiʻi, and the US Caribbean show the spatial distribution of temperature changes across the country at 3.6 degrees Fahrenheit (2 degrees Celsius) of global warming. The temperature change legend is in degrees Fahrenheit and values range from 0 to 1 (very light yellow) to 11 or more (dark red). An arrow labeled “global average” points to 3.6 degrees of warming. An arrow labeled “United States average” points to 5 degrees Fahrenheit. The maps show that changes are generally warmer at more northern latitudes. Increases are about 3 to 4 degrees across much of the southeast and Southern Great Plains and 4 to 5 degrees across most of the rest of the contiguous US. The Rocky Mountains and northern parts of the Northern Great Plains, Midwest, and Northeast show warming of 5 to 6 degrees. The US Caribbean warms 2 to 4 degrees, while Hawaii warms 3 to 4 degrees. Warming in Alaska follows a strong south to north gradient, with increases of 3 to 5 degrees in the south to 11 or more in the far north. Example changes at 3.6 degrees Fahrenheit of global warming are shown for each National Climate Assessment region, as follows: clockwise from top left: Alaska: Average winter temperatures increase by 4.8 degrees Fahrenheit. Northwest: Average summer temperatures increase by 3.9 degrees. Northern Great Plains: Nine fewer zero-degree days each year. Midwest: Ten more days above 95 degrees each year. Northeast: Minimum summer temperatures increase by 3.2 degrees. US Caribbean: Average summer temperatures increase by 1.7 degrees. Southeast: Six more days above 100 degrees each year. Southern Great Plains: Eight more days above 105 degrees each year. Southwest: Annual record high temperatures are 3.7 degrees hotter. Hawaii: Annual temperatures increase by 1.8 degrees.

What would 3.6°F (2°C) of global warming feel like in the United States?

Figure 1.14. As the world warms, the United States warms more on average. The map shows projected changes in annual surface temperature compared to the present day (1991–2020) under a global warming level of 3.6°F (2°C) above preindustrial levels (see Figure 2.9). Regional examples show how different temperature impacts would be experienced across the country at this level of warming. Figure credit: USGCRP, NOAA NCEI, and CISESS NC.

Warming increases risks to the US

Rising temperatures lead to many large-scale changes in Earth’s climate system, and the consequences increase with warming (Figure 1.15). Some of these changes can be further amplified through feedback processes at higher levels of warming, increasing the risk of potentially catastrophic outcomes. For example, uncertainty in the stability of ice sheets at high warming levels means that increases in sea level along the continental US of 3–7 feet by 2100 and 5–12 feet by 2150 are distinct possibilities that cannot be ruled out. The chance of reaching the upper end of these ranges increases as more warming occurs. In addition to warming more, the Earth warms faster in high and very high scenarios (SSP3-7.0 and SSP5-8.5, respectively), making adaptation more challenging. {2.3, 3.1, 3.4, 9.1}

Six horizontal bar charts illustrate the fact that consequences are greater at higher global warming levels. For the top four bar charts, the first bar indicates current values based on the average over 1991 to 2020. Four other bars show projected changes at 2.7, 3.6, 5.4 and 7.2 degrees Fahrenheit of global warming, respectively. The current values are indicated by darker shading and the changes from today are indicated by lighter shading. The top left chart is labeled US average temperature and text notes that the US warms more than the global average compared to the preindustrial period. The current temperature is about 53 degrees. Future values at the 4 warming levels range from nearly 56 degrees to almost 61 degrees. The top right chart is labeled number of days greater than or equal to 95 degrees, and text notes that the number of these very hot days increases. The current average is about 15 days per year. Future values range from almost 25 days per year to more than 50. The middle left chart is labeled annual average rainfall, and text notes that annual average rainfall totals increase rapidly in the north and more slowly in the south. Here, values are divided into north and south. The north currently averages about 29 inches per year, and future values range from more than 30 to more than 31 inches. In the south, the current value is more than 34 inches, and future values range from more than 35 to about 37. The middle right chart is labeled extreme precipitation events, with text noting that more rain falls during the most extreme precipitation events. The current value is about 2.2 inches. Future values range from more than 2.4 inches to almost 3.1 inches. The bottom left chart is labeled US average sea level rise, with text noting that sea level rise by 2100 compared to 2020 is higher for higher warming levels. No shading is used here, as the bars instead represent ranges of projections, and projections are for three warming levels: 2.7 degrees Fahrenheit, 3.6 degrees, and a range of 5.4 to 9 degrees. The current value is shown as about 5 inches. Future changes are about 18 to 35 inches, about 20 to about 37 inches, and about 24 to about 69 inches, respectively. The last bar has an asterisk indicating that the rise at the upper end of this range cannot be ruled out due to the possibility of rapid ice sheet loss. The amount of warming required to trigger such loss is not currently known but is assessed to be above 3.6 degrees Fahrenheit. The bottom right chart shows the number of coastal flooding events per year, with projections for the same three warming levels as in the sea level rise chart. Text notes that sea level rise drives an increase in the number of major coastal flooding events per year due to high tides alone. Current values are from 0.05 to 0.1. Future values are about 3, about 5, and about 182 events, respectively. 182 events per year translates into every other day.

At higher global warming levels, the US will experience more severe climate impacts.

Figure 1.15. With each additional increment of global warming, climate impacts in the US are projected to be more severe: US average temperature warms more than the global average (top left), and the number of days per year at or above 95°F in the US increases (top right). Annual average US rainfall increases rapidly in the North and more slowly in the South (center left), and more rain falls during the most extreme precipitation events (center right). Sea level rise (range of projected increases by 2100 compared to 2020) is higher (bottom left), driving an increase in the number of major coastal flooding events per year due to high tides alone (bottom right). Temperature (averages and extremely hot days; top row) and extreme rainfall projections (center right) are averages for all 50 states and Puerto Rico. Average rainfall projections (center left) are shown for both the northern and southern US (above and below 37° latitude, respectively). Sea level rise (bottom left) and coastal flooding (bottom right) projections are averages for the contiguous United States. For sea level change estimates outside of the contiguous US, see Chapter 23 (for Puerto Rico and the US Virgin Islands), Chapter 30 (for Hawaiʻi and the US-Affiliated Pacific Islands), and Sweet et al. 2022 (for Alaska). Global warming levels refer to warming since preindustrial temperature conditions, defined as the 1851–1900 average. Figure credit: USGCRP, NOAA NOS, NASA, NOAA NCEI, and CISESS NC.

How Climate Action Can Create a More Resilient and Just Nation

Large near-term cuts in greenhouse gas emissions are achievable through many currently available and cost-effective mitigation options. However, reaching net-zero emissions by midcentury cannot be achieved without exploring additional mitigation options. Even if the world decarbonizes rapidly, the Nation will continue to face climate impacts and risks. Adequately and equitably addressing these risks involves longer-term inclusive planning, investments in transformative adaptation, and mitigation approaches that consider equity and justice.

Available mitigation strategies can deliver substantial emissions reductions, but additional options are needed to reach net zero

Limiting global temperature change to well below 2°C (3.6°F) requires reaching net-zero CO₂ emissions globally by 2050 and net-zero emissions of all greenhouse gases from human activities within the following few decades (see “Meeting US mitigation targets means reaching net-zero emissions” above). Net-zero emissions pathways involve widespread implementation of currently available and cost-effective options for reducing emissions alongside rapid expansion of technologies and methods to remove carbon from the atmosphere to balance remaining emissions. However, to reach net-zero emissions, additional mitigation options need to be explored (Figure 1.16). Pathways to net zero involve large-scale technological, infrastructure, land-use, and behavioral changes and shifts in governance structures. {5.3, 6.3, 9.2, 9.3, 10.4, 13.2, 16.2, 18.4, 20.1, 24.1, 25.5, 30.5, 32.2, 32.3; Focus on Blue Carbon}

Scenarios that reach net-zero emissions include some of the following key options:

Decarbonizing the electricity sector, primarily through expansion of wind and solar energy, supported by energy storage {32.2}
Transitioning to transportation and heating systems that use zero-carbon electricity or low-carbon fuels, such as hydrogen {5.3, 13.1, 32.2, 32.3}
Improving energy efficiency in buildings, appliances, and light- and heavy-duty vehicles and other transportation modes {5.3, 13.3, 32.2}
Implementing urban planning and building design that reduces energy demands through more public transportation and active transportation and lower cooling demands for buildings {12.3, 13.1, 32.2}
Increasing the efficiency and sustainability of food production, distribution, and consumption {11.1, 32.2}
Improving land management to decrease greenhouse gas emissions and increase carbon removal and storage, with options ranging from afforestation, reforestation, and restoring coastal ecosystems to industrial processes that directly capture and store carbon from the air {5.3, 6.3, 8.3, 32.2, 32.3; Focus on Blue Carbon}

At left, a shaded area chart with text illustrates a portfolio of mitigation options for achieving net zero by 2050. The y axis of the chart shows millions of metric tons of carbon dioxide, with values ranging from negative 800 to positive 4,822, with the zero axis representing net-zero emissions. The x-axis ranges from 2020 to 2050 and beyond. Red shading above the zero axis indicates carbon dioxide emissions, while blue shading below the zero axis indicates carbon sinks. A white dashed line indicates net emissions. Emissions decrease from 4,822 in 2020 to 1,227 in 2050, with lighter shading indicating that decreases continue beyond 2050. Sinks increase from negative 800 in 2020 to negative 1,355 in 2050, with lighter shading indicating that increases continue beyond 2050. Stacked dots and a black bar indicate the range of emissions and sinks at 2050 as described in the caption. Text appears to the right of the chart. Under the heading reducing emissions, a subheading (in red) reads established opportunities with the following bulleted list: Improved energy efficiency, decarbonized electricity generation, electrified energy end uses, and improved efficiency of agricultural and food systems. Under the subheading additional opportunities (also in red), a bulleted list reads: hydrogen and other low-carbon fuels, carbon capture and storage, long-duration energy storage, and energy demand management. Under the heading increasing carbon uptake, a subheading (in blue) reads established opportunities, followed by text reading nature-based solutions that remove and store carbon, such as improved cropland and pasture management, avoided conversion of unmanaged lands, and afforestation and reforestation. Under the subheading additional opportunities (also in blue), a bulleted list reads: additional nature-based solutions, such as ocean carbon dioxide removal or blue carbon; biomass energy with carbon capture and storage; and technological direct air capture.

Reaching net zero by 2050 in the US will involve a mix of reductions in greenhouse gas emissions and increases in carbon dioxide removal.

Figure 1.16. Reaching net-zero emissions (horizontal white line) by midcentury in the US would mean deep reductions in emissions of carbon dioxide (CO₂) and other greenhouse gases (top side of figure; red), with residual emissions balanced by additional removal of CO₂ from the atmosphere (bottom side of figure; blue). The dashed white line shows net emissions to the atmosphere (the sum of carbon sources and carbon sinks). The dots at 2050 show ranges of emissions and uptake for energy model scenarios explored in detail in Chapter 32. Model scenarios that achieve these targets project a mix of established opportunities for reducing emissions and increasing carbon sinks. Among these, energy efficiency, decarbonized electricity (mainly renewables), and end-use electrification are critical for the energy sector. While not exhaustive, the list also includes additional opportunities, many of which are emerging technologies that will be integral to reaching net zero. These include options like use of hydrogen and low-carbon fuels to further reduce emissions in difficult-to-decarbonize sectors and greatly increasing CO₂ removal. Figure credit: EPA; University of California, Irvine; NOAA NCEI; and CISESS NC.

Due to large declines in technology and deployment costs over the last decade (Figure 1.2), decarbonizing the electricity sector is expected to be largely driven by rapid growth in renewable energy. Recent legislation is also expected to increase deployment rates of low- and zero-carbon technology. To reach net-zero targets, the US will need to add new electricity-generating capacity, mostly wind and solar, faster than ever before. This infrastructure expansion may drastically increase demand for products (batteries, solar photovoltaics) and resources, such as metals and critical minerals. Near-term shortages in minerals and metals due to increased demand can be addressed by increased recycling, for example, which can also reduce dependence on imported materials. {5.2, 5.3, 17.2, 25.3, 32.2, 32.4; Focus on Risks to Supply Chains}

Most US net-zero scenarios require CO₂ removal from the atmosphere to balance residual emissions, particularly from sectors where decarbonization is difficult. In these scenarios, nuclear and hydropower capacity are maintained but not greatly expanded; natural gas–fired generation declines, but more slowly if coupled with carbon capture and storage. {32.2}

Nature-based solutions that restore degraded ecosystems and preserve or enhance carbon storage in natural systems like forests, oceans, and wetlands, as well as agricultural lands, are cost-effective mitigation strategies. For example, with conservation and restoration, marine and coastal ecosystems could capture and store enough atmospheric carbon each year to offset about 3% of global emissions (based on 2019 and 2020 emissions). Many nature-based solutions can provide additional benefits, like improved ecosystem resilience, food production, improved water quality, and recreational opportunities. {8.3; Boxes 7.2, 32.2; Focus on Blue Carbon}

Adequately addressing climate risks involves transformative adaptation

While adaptation planning and implementation has advanced in the US, most adaptation actions to date have been incremental and small in scale (see Table 1.3). In many cases, more transformative adaptation will be necessary to adequately address the risks of current and future climate change. {31.1, 31.3}.

Table 1.3. Incremental Versus Transformative Adaptation Approaches

	Examples of incremental adaptation	Examples of transformative adaptation
	Using air-conditioning during heatwaves	Redesigning cities and buildings to address heat
	Reducing water consumption during droughts	Shifting water-intensive industry to match projected rainfall patterns
	Elevating homes above flood waters	Directing new housing development to less flood-prone areas

Transformative adaptation involves fundamental shifts in systems, values, and practices, including assessing potential trade-offs, intentionally integrating equity into adaptation processes, and making systemic changes to institutions and norms. While barriers to adaptation remain, many of these can be overcome with financial, cultural, technological, legislative, or institutional changes. {31.1, 31.2, 31.3}.

Adaptation planning can more effectively reduce climate risk when it identifies not only disparities in how people are affected by climate change but also the underlying causes of climate vulnerability. Transformative adaptation would involve consideration of both the physical and social drivers of vulnerability and how they interact to shape local experiences of vulnerability and disparities in risk. Examples include understanding how differing levels of access to disaster assistance constrain recovery outcomes or how disaster damage exacerbates long-term wealth inequality. Effective adaptation, both incremental and transformative, involves developing and investing in new monitoring and evaluation methods to understand the different values of, and impacts on, diverse individuals and communities. {9.3, 19.3, 31.2, 31.3, 31.5}

Transformative adaptation would require new and better-coordinated governance mechanisms and cooperation across all levels of government, the private sector, and society. A coordinated, systems-based approach can support consideration of risks that cut across multiple sectors and scales, as well as the development of context-specific adaptations. For example, California, Florida, and other states have used informal regional collaborations to develop adaptation strategies tailored to their area. Adaptation measures that are designed and implemented using inclusive, participatory planning approaches and leverage coordinated governance and financing have the greatest potential for long-term benefits, such as improved quality of life and increased economic productivity. {10.3, 18.4, 20.2, 31.4}

Mitigation and adaptation actions can result in systemic, cascading benefits

Actions taken now to accelerate net emissions reductions and adapt to ongoing changes can reduce risks to current and future generations. Mitigation and adaptation actions, from international to individual scales, can also result in a range of benefits beyond limiting harmful climate impacts, including some immediate benefits (Figure 1.1). The benefits of mitigation and proactive adaptation investments are expected to outweigh the costs. {2.3, 13.3, 14.5, 15.3, 17.4, 22.1, 31.6, 32.4; Introductions in Chs. 17, 31}

Accelerating the deployment of low-carbon technologies, expanding renewable energy, and improving building efficiency can have significant near-term social and economic benefits like reducing energy costs and creating jobs. {32.4}
Transitioning to a carbon-free, sustainable, and resilient transportation system can lead to improvements in air quality, fewer traffic fatalities, lower costs to travelers, improved mental and physical health, and healthier ecosystems. {13.3}
Reducing emissions of short-lived climate pollutants like methane, black carbon, and ozone provides immediate air quality benefits that save lives and decrease the burden on healthcare systems while also slowing near-term warming. {11.1, 14.5, 15.3}
Green infrastructure and nature-based solutions that accelerate pathways to net-zero emissions through restoration and protection of ecological resources can improve water quality, strengthen biodiversity, provide protection from climate hazards like heat extremes or flooding, preserve cultural heritage and traditions, and support more equitable access to environmental amenities. {8.3, 15.3, 20.3, 24.4, 30.4; Focus on Blue Carbon}
Strategic planning and investment in resilience can reduce the economic impacts of climate change, including costs to households and businesses, risks to markets and supply chains, and potential negative impacts on employment and income, while also providing opportunities for economic gain. {9.2, 19.3, 26.2, 31.6; Focus on Risks to Supply Chains}
Improving cropland management and climate-smart agricultural practices can strengthen the resilience and profitability of farms while also increasing soil carbon uptake and storage, reducing emissions of nitrous oxide and methane, and enhancing agricultural efficiency and yields. {11.1, 24.1, 32.2}

Climate actions that incorporate inclusive and sustained engagement with overburdened and underserved communities in the design, planning, and implementation of evidence-based strategies can also reduce existing disparities and address social injustices. {24.3, 31.2, 32.4}

Transformative climate actions can strengthen resilience and advance equity

Fossil fuel–based energy systems have resulted in disproportionate public health burdens on communities of color and/or low-income communities. These same communities are also disproportionately harmed by climate change impacts. {13.4, 15.2, 32.4}

A “just transition” is the process of responding to climate change with transformative actions that address the root causes of climate vulnerability while ensuring equitable access to jobs; affordable, low-carbon energy; environmental benefits such as reduced air pollution; and quality of life for all. This involves reducing impacts to overburdened communities, increasing resources to underserved communities, and integrating diverse worldviews, cultures, experiences, and capacities into mitigation and adaptation actions. As the country shifts to low-carbon energy industries, a just transition would include job creation and training for displaced fossil fuel workers and addressing existing racial and gender disparities in energy workforces. For example, Colorado agencies are creating plans to guide the state’s transition away from coal, with a focus on economic diversification, job creation, and workforce training for former coal workers. The state’s plan also acknowledges a commitment to communities disproportionately impacted by coal power pollution. {5.3, 13.4, 14.3, 15.2, 16.2, 20.3, 31.2, 32.4; Figure 20.1}

A just transition would take into account key aspects of environmental justice:

Recognizing that certain people have borne disparate burdens related to current and historical social injustices and, thus, may have different needs
Ensuring that people interested in and affected by outcomes of decision-making processes are included in those procedures through fair and meaningful engagement
Distributing resources and opportunities over time, including access to data and information, so that no single group or set of individuals receives disproportionate benefits or burdens

{20.3; Figure 20.1}

An equitable and sustainable US response to climate change has the potential to reduce climate impacts while improving well-being, strengthening resilience, benefiting the economy, and, in part, redressing legacies of racism and injustice. Transformative adaptation and the transition to a net-zero energy system come with challenges and trade-offs that would need to be considered to avoid exacerbating or creating new social injustices. For example, transforming car-centric transportation systems to emphasize public transit and walkability could increase accessibility for underserved communities and people with limited mobility—if user input and equity are intentionally considered. {13.4, 20.3, 31.3, 32.4; Ch. 31, Introduction}

Equitable responses that assess trade-offs strengthen community resilience and self-determination, often fostering innovative solutions. Engaging communities in identifying challenges and bringing together diverse voices to participate in decision-making allows for more inclusive, effective, and transparent planning processes that account for the structural factors contributing to inequitable climate vulnerability. {9.3, 12.4, 13.4, 20.2, 31.4}

The Fifth National Climate Assessment

Fifth National Climate Assessment
1. Overview
Understanding Risks, Impacts, and Responses

How the United States Is Addressing Climate Change

Future climate change impacts depend on choices made today

US emissions have decreased, while the economy and population have grown

Accelerating advances in adaptation can help reduce rising climate risks

Climate action has increased in every region of the US

Meeting US mitigation targets means reaching net-zero emissions

How the United States Is Experiencing Climate Change

Current climate changes are unprecedented over thousands of years

Risks from extreme events are increasing

Cascading and compounding impacts increase risks

Climate change exacerbates inequities

Harmful impacts will increase in the near term

Current and Future Climate Risks to the United States

Safe, reliable water supplies are threatened by flooding, drought, and sea level rise

Disruptions to food systems are expected to increase

Homes and property are at risk from sea level rise and more intense extreme events

Infrastructure and services are increasingly damaged and disrupted by extreme weather and sea level rise

Climate change exacerbates existing health challenges and creates new ones

Ecosystems are undergoing transformational changes

Climate change slows economic growth, while climate action presents opportunities

Many regional economies and livelihoods are threatened by damages to natural resources and intensifying extremes

Job opportunities are shifting due to climate change and climate action

Climate change is disrupting cultures, heritages, and traditions

The Choices That Will Determine the Future

Societal choices drive greenhouse gas emissions

Rising global emissions are driving global warming, with faster warming in the US

Warming increases risks to the US

How Climate Action Can Create a More Resilient and Just Nation

Available mitigation strategies can deliver substantial emissions reductions, but additional options are needed to reach net zero

Adequately addressing climate risks involves transformative adaptation

Mitigation and adaptation actions can result in systemic, cascading benefits

Transformative climate actions can strengthen resilience and advance equity

Likelihood

Confidence Level

The Fifth National Climate Assessment

How the United States Is Addressing Climate Change

Future climate change impacts depend on choices made today

US emissions have decreased, while the economy and population have grown

Accelerating advances in adaptation can help reduce rising climate risks

Climate action has increased in every region of the US

Meeting US mitigation targets means reaching net-zero emissions

How the United States Is Experiencing Climate Change

Current climate changes are unprecedented over thousands of years

Risks from extreme events are increasing

Cascading and compounding impacts increase risks

Climate change exacerbates inequities

Harmful impacts will increase in the near term

Current and Future Climate Risks to the United States

Safe, reliable water supplies are threatened by flooding, drought, and sea level rise

Disruptions to food systems are expected to increase

Homes and property are at risk from sea level rise and more intense extreme events

Infrastructure and services are increasingly damaged and disrupted by extreme weather and sea level rise

Climate change exacerbates existing health challenges and creates new ones

Ecosystems are undergoing transformational changes

Climate change slows economic growth, while climate action presents opportunities

Many regional economies and livelihoods are threatened by damages to natural resources and intensifying extremes

Job opportunities are shifting due to climate change and climate action

Climate change is disrupting cultures, heritages, and traditions

The Choices That Will Determine the Future

Societal choices drive greenhouse gas emissions

Rising global emissions are driving global warming, with faster warming in the US

Warming increases risks to the US

How Climate Action Can Create a More Resilient and Just Nation

Available mitigation strategies can deliver substantial emissions reductions, but additional options are needed to reach net zero

Adequately addressing climate risks involves transformative adaptation

Mitigation and adaptation actions can result in systemic, cascading benefits

Transformative climate actions can strengthen resilience and advance equity

Cover image

Likelihood

Confidence Level