EPA - Climate Change Science (2024)

Link: https://www.epa.gov/climatechange-science/basics-climate-change

Please see link above for source text.

The following was taken from the U.S. Environmental Protection Agency website on December 30, 2024.

Basics of Climate Change

Learn about some of the key concepts related to climate change:

● The Greenhouse Effect

● Key Greenhouse Gases

● Other Greenhouse Gases

● Aerosols

● Climate Feedbacks

More Climate Change Information

● See answers to common questions on climate change on the Frequently Asked Questions page

● Observations across the United States are showing how climate change is happening now. Learn more about Climate Change Indicators.

The earth's climate is changing. Multiple lines of evidence show changes in our weather, oceans, and ecosystems, such as:

● Changing temperature and precipitation patterns 1

● Increases in ocean temperatures, sea level, and acidity.2

● Melting of glaciers and sea ice.3

● Changes in the frequency, intensity, and duration of extreme weather events.4

● Shifts in ecosystem characteristics, like the length of the growing season, timing of flower blooms, and migration of birds.

These changes are due to a buildup of greenhouse gases in our atmosphere and the warming of the planet due to the greenhouse effect.

Atmospheric Data Trapped In Ice

Source: Smithsonian National Museum of Natural History, 2018

The Greenhouse Effect

The greenhouse effect helps trap heat from the sun, which keeps the temperature on earth comfortable. But people’s activities are increasing the amount of heattrapping greenhouse gases in the atmosphere, causing the earth to warm up.

The earth's temperature depends on the balance between energy entering and leaving the planet’s system. When sunlight reaches the earth’s surface, it can either be reflected back into space or absorbed by the earth. Incoming energy that is

absorbed by the earth warms the planet. Once absorbed, the planet releases some of the energy back into the atmosphere as heat (also called infrared radiation). Solar energy that is reflected back to space does not warm the earth.

Certain gases in the atmosphere absorb energy, slowing or preventing the loss of heat to space. Those gases are known as “greenhouse gases.” They act like a blanket, making the earth warmer than it would otherwise be. This process, commonly known as the “greenhouse effect,” is natural and necessary to support life. However, the recent buildup of greenhouse gases in the atmosphere from human activities has changed the earth's climate and resulted in dangerous effects to human health and welfare and to ecosystems.

Key Greenhouse Gases

Most of the warming since 1950 has been caused by human emissions of greenhouse gases 5,6 Greenhouse gases come from a variety of human activities, including burning fossil fuels for heat and energy, clearing forests, fertilizing crops, storing waste in landfills, raising livestock, and producing some kinds of industrial products.

Carbon Dioxide

Carbon dioxide is the primary greenhouse gas contributing to recent climate change. Carbon dioxide enters the atmosphere through burning fossil fuels, solid waste, trees, and other biological materials, and as a result of certain chemical reactions, such as cement manufacturing. Carbon dioxide is absorbed and emitted naturally as part of the carbon cycle, through plant and animal respiration, volcanic eruptions, and ocean-atmosphere exchange.

The Carbon Cycle

The carbon cycle is the process by which carbon continually moves from the

atmosphere to the earth and then back to the atmosphere. On the earth, carbon is stored in rocks, sediments, the ocean, and in living organisms. Carbon is released back into the atmosphere when plants and animals die, as well as when fires burn, volcanoes erupt, and fossil fuels (such as coal, natural gas, and oil) are combusted. The carbon cycle ensures there is a balanced concentration of carbon in the different reservoirs on the planet. But a change in the amount of carbon in one reservoir affects all the others. Today, people are disturbing the carbon cycle by burning fossil fuels, which release large amounts of carbon dioxide into the atmosphere, and through land use changes that remove plants, which absorb carbon from the atmosphere.

Source: Smithsonian National Museum of Natural History, May 30, 2019

Methane

Both natural and human activities produce methane. For example, natural wetlands, agricultural activities, and fossil fuel extraction and transport all emit methane.

Nitrous Oxide

Nitrous oxide is produced mainly through agricultural activities and natural biological processes. Fossil fuel burning and industrial processes also create nitrous oxide.

F-Gases

Chlorofluorocarbons, hydrochlorofluorocarbons, hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride, together called F-gases, are often used in coolants, foaming agents, fire extinguishers, solvents, pesticides, and aerosol propellants.

Global Warming Potential

Different greenhouse gases can remain in the atmosphere for different amounts of

time, ranging from a few years to thousands of years. In addition, some gases are more effective than others at making the planet warmer. Learn more about Global Warming Potential (GWP), a measure of climate impacts based on how long each greenhouse gas remains in the atmosphere and how strongly it absorbs energy.

Other Greenhouse Gases

Ground-Level Ozone

Ground-level ozone is created by a chemical reaction between emissions of nitrogen oxides and volatile organic compounds from automobiles, power plants, and other industrial and commercial sources in the presence of sunlight. In addition to trapping heat, ground-level ozone is a pollutant that can cause respiratory health problems and damage crops and ecosystems.

Water Vapor

Water vapor is another greenhouse gas and plays a key role in climate feedbacks because of its heat-trapping ability. Warmer air holds more moisture than cooler air. Therefore, as greenhouse gas concentrations increase and global temperatures rise, the total amount of water vapor in the atmosphere also increases, further amplifying the warming effect.7

For more information on greenhouse gases, see Greenhouse Gas Emissions

Aerosols

Aerosols in the atmosphere can affect climate. Aerosols are microscopic (solid or liquid) particles that are so small that instead of quickly falling to the surface like larger particles, they remain suspended in the air for days to weeks. Human activities, such as burning fossil fuels and biomass, contribute to emissions of these substances, although some aerosols also come from natural sources such as volcanoes and marine plankton.

Unlike greenhouse gases, the climate effects of aerosols vary depending on what they are made of and where they are emitted. Depending on their color and other factors, aerosols can either absorb or reflect sunlight. Aerosols that reflect sunlight, such as particles from volcanic eruptions or sulfur emissions from burning coal, have a cooling effect. Those that absorb sunlight, such as black carbon (a part of soot), have a warming effect.

Not only can black carbon directly absorb incoming and reflected sunlight, but it can also absorb infrared radiation.8 Black carbon can also be deposited on snow and ice, darkening the surface and thereby increasing the snow's absorption of sunlight and accelerating melt.8 For more information, see the 2015 Report to Congress on Black Carbon. While reductions in all aerosols can lead to more warming, targeted reductions in black carbon emissions can reduce global warming. Warming and cooling aerosols can also interact with clouds, changing their ability to form and dissipate, as well as their reflectivity and precipitation rates. Clouds can contribute both to cooling, by reflecting sunlight, and warming, by trapping outgoing heat.

Climate Feedbacks

Climate feedbacks are natural processes that respond to global warming by offsetting or further increasing change in the climate system. Feedbacks that offset the change in climate are called negative feedbacks. Feedbacks that amplify changes are called positive feedbacks.

Water vapor appears to cause the most important positive feedback. As the earth warms, the rate of evaporation and the amount of water vapor in the air both increase. Because water vapor is a greenhouse gas, this leads to further warming.

The melting of Arctic sea ice is another example of a positive climate feedback. As temperatures rise, sea ice retreats. The loss of ice exposes the underlying sea surface, which is darker and absorbs more sunlight than ice, increasing the total amount of warming. Less snow cover during warm winters has a similar effect.

Clouds can have both warming and cooling effects on climate. They cool the planet

by reflecting sunlight during the day, and they warm the planet by slowing the escape of heat to space (this is most apparent at night, as cloudy nights are usually warmer than clear nights).

Climate change can lead to changes in the coverage, altitude, and reflectivity of clouds. These changes can then either amplify (positive feedback) or dampen (negative feedback) the original change. The net effect of these changes is likely an amplifying, or positive, feedback due mainly to increasing altitude of high clouds in the tropics, which makes them better able to trap heat, and reductions in coverage of lower-level clouds in the mid-latitudes, which reduces the amount of sunlight they reflect. The magnitude of this feedback is uncertain due to the complex nature of cloud/climate interactions.9

1 Marvel, K. et al. (2023). Ch. 2: Climate Trends. Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC, p. 2-11.

2 Ibid, p. 2-14.

3 Ibid, p. 2-10.

4 Ibid, p. 2-16.

5National Academy of Sciences. (2020). Climate change: evidence and causes: Update 2020. The National Academies Press, Washington, DC, p. 5. doi: 10.17226/25733

6 Wuebbles, D.J., D.W. Fahey, K.A. Hibbard, B. DeAngelo, S. Doherty, K. Hayhoe, R. Horton, J.P. Kossin, P.C. Taylor, A.M. Waple, and C.P. Weaver. (2017). Executive summary. In: Climate science special report: Fourth national climate assessment, volume I [Wuebbles, D.J., D.W. Fahey, K.A. Hibbard, D.J. Dokken, B.C. Stewart, & T.K. Maycock (eds.)]. U.S. Global Change Research Program, Washington, DC, p. 14. doi: 10.7930/J0DJ5CTG

7Leung, L. R. et al (2023) Ch. 3 Earth Systems Processes. Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC, p. 3-42.

8Myhre, G., D. Shindell, F.-M. Bréon, W. Collins, J. Fuglestvedt, J. Huang, D. Koch, J.-F. Lamarque, D. Lee, B. Mendoza, T. Nakajima, A. Robock, G. Stephens, T. Takemura & H. Zhang. (2013). Anthropogenic

and natural radiative forcing. In: Climate change 2013: The physical science basis. Working Group I contribution to the fifth assessment report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom, and New York, NY, p. 685.

9Leung, L.R. et al. (2023). Ch. 3: Earth Systems Processes. Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC, p. 3-37.

Climate Change Science

Basics Causes Impacts

Future of Climate Change

Frequently Asked Questions

Contact Us About Climate Change Science

Last updated on November 7, 2024

Causes of Climate Change

Human and natural factors both influence the earth’s climate, but the long-term trend observed over the past century can only be explained by the effect of human activities on climate. Source: U.S. Global Change Research Program, Fourth National Climate Assessment, Chapter 2: Our Changing Climate, 2017. Since the Industrial Revolution, human activities have released large amounts of carbon dioxide and other greenhouse gases into the atmosphere, which has changed the earth’s climate. Natural processes, such as changes in the sun's energy and volcanic eruptions, also affect the earth's climate. However, they do not explain the warming that we have observed over the last century.1,2

Human Versus Natural Causes

Scientists have pieced together a record of the earth’s climate by analyzing a number of indirect measures of climate, such as ice cores, tree rings, glacier

lengths, pollen remains, and ocean sediments, and by studying changes in the earth’s orbit around the sun.3,4 This record shows that the climate varies naturally over a wide range of time scales, but this variability does not explain the observed warming since the 1950s. Rather, it is extremely likely (> 95%) that human activities have been the dominant cause of that warming.5,6

It is unequivocal that human influence has warmed the atmosphere, ocean and land.

Intergovernmental Panel on Climate Change (2021 Report)7

Human activities have contributed substantially to climate change through:

● Greenhouse Gas Emissions

● Reflectivity or Absorption of the Sun’s Energy

Heat-trapping Greenhouse Gases And The Earth's Climate

Source: Smithsonian National Museum of Natural History, 2018

Greenhouse Gases

This graph shows the increase in atmospheric concentrations of three of the key greenhouse gases over the last 2,000 years. Increases in concentrations of these gases since 1750 are due to human activities in the industrial era. Source: U.S. EPA, Climate Change Indicators in the United States: Atmospheric Concentrations of Greenhouse Gases, 2021.

Concentrations of the key greenhouse gases have all increased since the Industrial Revolution due to human activities. Carbon dioxide, methane, and nitrous oxide

concentrations are now more abundant in the earth’s atmosphere than any time in the last 800,000 years.8,9 These greenhouse gas emissions have increased the greenhouse effect and caused the earth’s surface temperature to rise. Burning fossil fuels changes the climate more than any other human activity.

Carbon dioxide: In recent years, human activities have released around 35 billion tons of carbon dioxide into the atmosphere every year.10 Atmospheric carbon dioxide concentrations have increased by more than 40 percent since pre-industrial times, from approximately 280 parts per million (ppm) in the 18th century11 to 419 ppm in 2023.12

Methane: Human activities increased methane concentrations during most of the 20th century to more than 2.5 times the pre-industrial level, from approximately 722 parts per billion (ppb) in the 18th century13 to 1,922 ppb in 2023.14

Nitrous oxide: Nitrous oxide concentrations have risen approximately 20 percent since the start of the Industrial Revolution, with a relatively rapid increase toward the end of the 20th century. Nitrous oxide concentrations have increased from a preindustrial level of 270 ppb15 to 337 ppb in 2023.16

Additional Resources about Greenhouse Gases

● Greenhouse Gas Emissions and Removals: more information on greenhouse gas emissions

● What You Can Do About Climate Change: learn more about actions that you can take to reduce greenhouse gas emissions

● EPA's Greenhouse Gas Equivalencies Calculator: translate abstract greenhouse gas emissions measurements into concrete terms

Reflectivity or Absorption of the Sun’s Energy

Activities such as agriculture, road construction, and deforestation can change the reflectivity of the earth's surface, leading to local warming or cooling. This effect is observed in heat islands, which are urban centers that are warmer than the

surrounding, less populated areas. One reason that these areas are warmer is that buildings, pavement, and roofs tend to reflect less sunlight than natural surfaces. While deforestation can increase the earth’s reflectivity globally by replacing dark trees with lighter surfaces such as crops, the net effect of all land-use changes appears to be a small cooling.17

Emissions of small particles, known as aerosols, into the air can also lead to reflection or absorption of the sun's energy. Many types of air pollutants undergo chemical reactions in the atmosphere to create aerosols. Overall, human-generated aerosols have a net cooling effect on the earth. Learn more about human-generated and natural aerosols.

Natural Processes

Natural processes are always influencing the earth’s climate and can explain climate changes prior to the Industrial Revolution in the 1700s. However, recent climate changes cannot be explained by natural causes alone.

Changes in the Earth’s Orbit and Rotation

Changes in the earth’s orbit and its axis of rotation have had a big impact on climate in the past. For example, the amount of summer sunshine on the Northern Hemisphere, which is affected by changes in the planet’s orbit, appears to be the primary cause of past cycles of ice ages, in which the earth has experienced long periods of cold temperatures (ice ages), as well as shorter interglacial periods (periods between ice ages) of relatively warmer temperatures.18 At the coldest part of the last glacial period (or ice age), the average global temperature was about 11°F colder than it is today. At the peak of the last interglacial period, however, the average global temperature was at most 2°F warmer than it is today.19

Variations in Solar Activity

Changes in the sun’s energy output can affect the intensity of the sunlight that reaches the earth’s surface. While these changes can influence the earth’s climate, solar variations have played little role in the climate changes observed in recent decades.20 Satellites have been measuring the amount of energy the earth receives from the sun since 1978. These measurements show no net increase in the sun’s output, even as global surface temperatures have risen.21

The sun follows a natural 11-year cycle of small ups and downs in intensity (bottom chart), but the effect on the earth is small. Over the same period, the average global temperature has increased markedly (top chart). Source: National Academy of Sciences, Climate Change Evidence & Causes, 2020.

Changes in the Earth’s Reflectivity

The amount of sunlight that is absorbed or reflected by the planet depends on the

earth’s surface and atmosphere. Dark objects and surfaces, like the ocean, forests, and soil, tend to absorb more sunlight. Light-colored objects and surfaces, like snow and clouds, tend to reflect sunlight. About 70 percent of the sunlight that reaches the earth is absorbed.22 Natural changes in the earth’s surface, like the melting of sea ice, have contributed to climate change in the past, often acting as feedbacks to other processes.

Volcanic Activity

Volcanoes have played a noticeable role in climate, and volcanic eruptions released large quantities of carbon dioxide in the distant past. Some explosive volcano eruptions can throw particles (e.g., SO2) into the upper atmosphere, where they can reflect enough sunlight back to space to cool the surface of the planet for several years.23 These particles are an example of cooling aerosols.

Volcanic particles from a single eruption do not produce long-term climate change because they remain in the atmosphere for a much shorter time than greenhouse gases. In addition, human activities emit more than 100 times as much carbon dioxide as volcanoes each year.24

Changes in Naturally Occurring Carbon Dioxide Concentrations

Over the last several hundred thousand years, carbon dioxide levels varied in tandem with the glacial cycles. During warm interglacial periods, carbon dioxide levels were higher. During cool glacial periods, carbon dioxide levels were lower.25 The heating or cooling of the earth’s surface and oceans can cause changes in the natural sources and sinks of these gases, and thus change greenhouse gas concentrations in the atmosphere.26 These changing concentrations have acted as a positive climate feedback, amplifying the temperature changes caused by long-term shifts in the earth’s orbit.27

Analyses of ice core data extending back 800,000 years show that warmer periods on the earth coincide with periods of relatively high atmospheric carbon dioxide concentrations. Source: Based on data appearing in NAS, Climate Change Evidence & Causes, 2020.

1 National Academy of Sciences. (2020). Climate change: Evidence and causes: Update 2020. The National Academies Press, Washington, DC, p. 5. doi: 10.17226/25733

2 Frazier, A. et al. (2023). Ch. 2: Climate Trends. Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC, p. 2-4.

3 Wuebbles, D.J., D.W. Fahey, K.A. Hibbard, B. DeAngelo, S. Doherty, K. Hayhoe, R. Horton, J.P. Kossin, P.C. Taylor, A.M. Waple & C.P. Weaver. (2017). Executive summary. In: Climate science special report: Fourth national climate assessment, volume I [Wuebbles, D.J., D.W. Fahey, K.A. Hibbard, D.J. Dokken, B.C. Stewart & T.K. Maycock (eds.)]. U.S. Global Change Research Program, Washington, DC, pp. 12–34, doi: 10.7930/J0DJ5CTG

4 National Academy of Sciences. (2020). Climate change: Evidence and causes: Update 2020. The National Academies Press, Washington, DC, pp. 3-5. doi: 10.17226/25733

5 IPCC (2013). Climate change 2013: The physical science basis Working Group I contribution to the fifth assessment report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex & P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, p. 869.

6 Frazier, A. et al. (2023). Ch. 2: Climate Trends. Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC, p. 2-4.

7 IPCC. (2021). Climate change 2021: The physical science basis Working Group I contribution to the sixth assessment report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu & B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom, p. SPM-5.

8 Fahey, D.W., S.J. Doherty, K.A. Hibbard, A. Romanou & P.C. Taylor. (2017). Physical drivers of climate change. In: Climate science special report: Fourth national climate assessment, volume I [Wuebbles, D.J., D.W. Fahey, K.A. Hibbard, D.J. Dokken, B.C. Stewart & T.K. Maycock (eds.)]. U.S. Global Change Research Program, Washington, DC, p. 80, Figure 2.4. doi: 10.7930/J0513WCR

9 Jay, A.K. et al. (2023). Ch. 1: Overview. Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC, p. 1-17.

10 IEA (2024), CO2 Emissions in 2023, IEA, Paris. https://www.iea.org/reports/co2-emissions-in-2023

11 IPCC. (2013). Climate change 2013: The physical science basis Working Group I contribution to the fifth assessment report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex & P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom, and New York, NY, p. 166.

12 Lan, X., Tans, P. and K.W. Thoning: Trends in globally-averaged CO2 determined from NOAA Global Monitoring Laboratory measurements. Version 2024-11 https://doi.org/10.15138/9N0H-ZH07. Retrieved 11/7/2024 from globally averaged marine surface annual mean data.

13 IPCC. (2013). Climate change 2013: The physical science basis Working Group I contribution to the fifth assessment report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex & P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom, and New York, NY, p. 167.

14 Lan, X., K.W. Thoning, and E.J. Dlugokencky: Trends in globally-averaged CH4, N2O, and SF6 determined from NOAA Global Monitoring Laboratory measurements. Version 2024-11,

https://doi.org/10.15138/P8XG-AA10. Retrieved 11/7/2024 from globally averaged marine surface annual mean data.

15 IPCC. (2013). Climate change 2013: The physical science basis Working Group I contribution to the fifth assessment report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex & P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom, and New York, NY, p. 168.

16 Lan, X., K.W. Thoning, and E.J. Dlugokencky: Trends in globally-averaged CH4, N2O, and SF6 determined from NOAA Global Monitoring Laboratory measurements. Version 2024-11, https://doi.org/10.15138/P8XG-AA10. Retrieved 11/7/2024 from globally averaged marine surface annual mean data.

17 Fahey, D.W., S.J. Doherty, K.A. Hibbard, A. Romanou & P.C. Taylor. (2017). Physical drivers of climate change. In: Climate science special report: Fourth national climate assessment, volume I [Wuebbles, D.J., D.W. Fahey, K.A. Hibbard, D.J. Dokken, B.C. Stewart & T.K. Maycock (eds.)]. U.S. Global Change Research Program, Washington, DC, p. 78, Fig. 2.3 and p. 86. doi: 10.7930/J0513WCR

18 National Academy of Sciences. (2020). Climate change: Evidence and causes: Update 2020. The National Academies Press, Washington, DC, p. 9. doi: 10.17226/25733

19 Fahey, D.W., S.J. Doherty, K.A. Hibbard, A. Romanou & P.C. Taylor. (2017). Our globally changing climate. In: Climate science special report: Fourth national climate assessment, volume I [Wuebbles, D.J., D.W. Fahey, K.A. Hibbard, D.J. Dokken, B.C. Stewart & T.K. Maycock (eds.)]. U.S. Global Change Research Program, Washington, DC, p. 53. doi: 10.7930/J08S4N35

20Leung, L.R. et al. (2023). Ch. 3: Earth Systems Processes. Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC, p. 3-5.

21 National Academy of Sciences. (2020). Climate change: Evidence and causes: Update 2020. The National Academies Press, Washington, DC, p. 7. doi: 10.17226/25733

22 Fahey, D.W., S.J. Doherty, K.A. Hibbard, A. Romanou, & P.C. Taylor. (2017). Physical drivers of climate change. In: Climate science special report: Fourth national climate assessment, volume I [Wuebbles, D.J., D.W. Fahey, K.A. Hibbard, D.J. Dokken, B.C. Stewart & T.K. Maycock (eds.)]. U.S. Global Change Research Program, Washington, DC, p. 2. doi: 10.7930/J0513WCR

23 Fahey, D.W., S.J. Doherty, K.A. Hibbard, A. Romanou, & P.C. Taylor. (2017). Physical drivers of climate change. In: Climate science special report: Fourth national climate assessment, volume I [Wuebbles, D.J., D.W. Fahey, K.A. Hibbard, D.J. Dokken, B.C. Stewart & T.K. Maycock (eds.)]. U.S.

Global Change Research Program, Washington, DC, p. 79. doi: 10.7930/J0513WCR

24 Fahey, D.W., S.J. Doherty, K.A. Hibbard, A. Romanou & P.C. Taylor. (2017). Physical drivers of climate change. In: Climate science special report: Fourth national climate assessment, volume I [Wuebbles, D.J., D.W. Fahey, K.A. Hibbard, D.J. Dokken, B.C. Stewart & T.K. Maycock (eds.)]. U.S. Global Change Research Program, Washington, DC, p. 79. doi: 10.7930/J0513WCR

25 National Academy of Sciences. (2020). Climate change: Evidence and causes: Update 2020. The National Academies Press, Washington, DC, pp. 9–10. doi: 10.17226/25733

26 IPCC. (2013). Climate change 2013: The physical science basis Working Group I contribution to the fifth assessment report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex & P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, p. 399.

27 National Academy of Sciences. (2020). Climate change: Evidence and causes: Update 2020. The National Academies Press, Washington, DC, pp. 9–10. doi: 10.17226/25733

Climate Change Science

Basics Causes Impacts

Future of Climate Change

Frequently Asked Questions

Contact Us About Climate Change Science

Last updated on December 4, 2024

Impacts of Climate Change

Climate change is happening. Global average temperature has increased about 1.7°F from 1970 to 2023.1 Changes of one or two degrees in the average temperature of the planet can cause potentially dangerous shifts in climate and weather. These real, observable changes are what we call climate change impacts because they are the visible ways that climate change is affecting the Earth. For example, many places have experienced changes in rainfall, resulting in more floods, droughts, or intense rain, as well as more frequent and severe heat waves.

The planet's oceans and glaciers have also experienced changes—oceans are warming and becoming more acidic, ice caps are melting, and sea level is rising. As these and other changes become more pronounced in the coming decades, they will likely present challenges to our society and our environment.

More on Climate Change Impacts

Climate change is happening globally, but the effects can differ locally. Certain sectors, regions, and human populations are more vulnerable or have unique risks due to climate change. To learn more about the differing impacts faced by these parts of our environment and society, visit the Climate Change Impacts web area

Seeing the Impacts

Climate change impacts our health, environment, and economy. For example:

● Warmer temperatures increase the frequency, intensity, and duration of heat waves,2, 3, 4which can pose health risks, particularly for young children and

the elderly

● Climate change can also impact human health by worsening air and water quality, increasing the spread of certain diseases, and altering the frequency or intensity of extreme weather events.5

● Rising sea level threatens coastal communities and ecosystems.6

● Changes in the patterns and amount of rainfall, as well as changes in the timing and amount of stream flow, can affect water supplies and water quality and the production of hydroelectricity.7

● Changing ecosystems influence geographic ranges of many plant and animal species and the timing of their lifecycle events, such as migration and reproduction.8

● Increases in the frequency and intensity of extreme weather events, such as heat waves, droughts, and floods, can increase losses to property, cause costly disruptions to society, and reduce the affordability of insurance.9, 10, 11, 12, 13,14

Calving front of the Upsala Glacier (Argentina). Source: NASA, NASA Image and Video Library, 2017.

California’s Woolsey wildfire from 2018 which burned over 96 thousand acres.

Looking Ahead

Elevated concentrations of carbon dioxide will persist in the atmosphere for hundreds or thousands of years, so the earth will continue to warm in the coming decades. The warmer it gets, the greater the risk for more severe changes to the climate and the earth's system. Although it's difficult to predict the exact impacts of climate change, what's clear is that the climate we are accustomed to is no longer a reliable guide for what to expect in the future.

Adapting to Climate Change

Adaptation helps us prepare for some of the likely effects of climate change by reducing their impacts on ecosystems and people's well-being. Examples of adaptation include strengthening water conservation programs, upgrading stormwater systems, developing early warning systems for extreme heat events, and preparing for stronger storms through better emergency preparation and response strategies.

1 Frazier, A. et al. (2023). Ch. 2: Climate Trends. Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC, p. 2-11.

2 Hayden M.H. et al. (2023). Ch. 15: Human Health. Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC, p. 15-6.

3Ebi, K.L., J.M. Balbus, G. Luber, A. Bole, A. Crimmins, G. Glass, S. Saha, M.M. Shimamoto, J. Trtanj & J.L. White-Newsome. (2018). Human health. In: Impacts, risks, and adaptation in the United States: Fourth national climate assessment, volume II [Reidmiller, D.R., C.W. Avery, D.R. Easterling, K.E. Kunkel, K.L.M. Lewis, T.K. Maycock, and B.C. Stewart (eds.)]. U.S. Global Change Research Program, Washington, DC, pp. 544, 551–552. doi: 10.7930/NCA4.2018.CH14

4Sarofim, M.C., S. Saha, M.D. Hawkins, D.M. Mills, J. Hess, R. Horton, P. Kinney, J. Schwartz & A. St. Juliana. (2016). Temperature-related death and illness. In: The impacts of climate change on human health in the United States: A scientific assessment. U.S. Global Change Research Program, Washington, DC, pp. 43-68. doi: 10.7930/J0MG7MDX

5 Hayden M.H. et al. (2023). Ch. 15: Human Health. Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC, p. 15-6.

6 May, C.L. et al. (2023). Ch. 9: Coastal Effects. Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC, p. 9-5.

7 Lall, U., T. Johnson, P. Colohan, A. Aghakouchak, C. Brown, G. McCabe, R. Pulwarty & A. Sankarasubramanian. (2018). Water. In: Impacts, risks, and adaptation in the United States: Fourth national climate assessment, volume II [Reidmiller, D.R., C.W. Avery, D.R. Easterling, K.E. Kunkel, K.L.M. Lewis, T.K. Maycock & B.C. Stewart (eds.)]. U.S. Global Change Research Program, Washington, DC, pp. 145–173. doi: 10.7930/NCA4.2018.CH3

8 May, C.L. et al. (2023). Ch. 8: Ecosystems, Ecosystem Services, and Biodiversity. Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC, p. 8-18.

9 Ebi, K.L., J.M. Balbus, G. Luber, A. Bole, A. Crimmins, G. Glass, S. Saha, M.M. Shimamoto, J. Trtanj & J.L. White-Newsome. (2018). Human health. In: Impacts, risks, and adaptation in the United States: Fourth national climate assessment,

volume II [Reidmiller, D.R., C.W. Avery, D.R. Easterling, K.E. Kunkel, K.L.M. Lewis, T.K. Maycock, and B.C. Stewart (eds.)]. U.S. Global Change Research Program, Washington, DC, pp. 544, 551–552. doi: 10.7930/NCA4.2018.CH14

10 Vose, R.S., D.R. Easterling, K.E. Kunkel, A.N. LeGrande & M.F. Wehner. (2017).

Temperature changes in the United States. In: Climate science special report: Fourth national climate assessment, volume I [Wuebbles, D.J., D.W. Fahey, K.A. Hibbard, D.J. Dokken, B.C. Stewart & T.K. Maycock (eds.)]. U.S. Global Change Research Program, Washington, DC, pp. 197–199. doi: 10.7930/J0N29V45

11Gowda, P., J.L. Steiner, C. Olson, M. Boggess, T. Farrigan & M.A. Grusak. (2018).

Agriculture and rural communities. In: Impacts, risks, and adaptation in the United States: Fourth national climate assessment, volume II [Reidmiller, D.R., C.W. Avery, D.R. Easterling, K.E. Kunkel, K.L.M. Lewis, T.K. Maycock & B.C. Stewart (eds.)]. U.S. Global Change Research Program, Washington, DC, pp. 399–403. doi: 10.7930/NCA4.2018.CH10

12Hayhoe, K., D.J. Wuebbles, D.R. Easterling, D.W. Fahey, S. Doherty, J. Kossin, W. Sweet, R. Vose & M. Wehner. (2018). Our changing climate. In: Impacts, risks, and adaptation in the United States: Fourth national climate assessment, volume II [Reidmiller, D.R., C.W. Avery, D.R. Easterling, K.E. Kunkel, K.L.M. Lewis, T.K. Maycock & B.C. Stewart (eds.)]. U.S. Global Change Research Program, Washington, DC, pp. 88–90. doi: 10.7930/NCA4.2018.CH2

13Wehner, M.F., J.R. Arnold, T. Knutson, K.E. Kunkel & A.N. LeGrande. (2017). Droughts, floods, and wildfires. In: Climate science special report: Fourth national climate assessment, volume I [Wuebbles, D.J., D.W. Fahey, K.A. Hibbard, D.J. Dokken, B.C. Stewart & T.K. Maycock (eds.)]. U.S. Global Change Research Program, Washington, DC, pp. 237–240 and 240–242. doi: 10.7930/J0CJ8BNN

14Fleming, E., J. Payne, W. Sweet, M. Craghan, J. Haines, J.F. Hart, H. Stiller & A. Sutton-Grier. (2018). Coastal effects. In: Impacts, risks, and adaptation in the United

States: Fourth national climate assessment, volume II [Reidmiller, D.R., C.W. Avery, D.R. Easterling, K.E. Kunkel, K.L.M. Lewis, T.K. Maycock & B.C. Stewart (eds.)].

U.S. Global Change Research Program, Washington, DC, p. 339. doi: 10.7930/NCA4.2018.CH8

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Future of Climate Change

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Contact Us About Climate Change Science

Last updated on November 1, 2024

Future of Climate Change

The Future Climate Depends on Our Actions Today

Future climate conditions depend on what we do today. To mitigate the negative impacts of climate change, the world needs to drastically reduce its greenhouse gas emissions.

Learn more about what EPA is doing about climate change and what you can do. Since the Industrial Revolution, human activities have released large amounts of carbon dioxide and other greenhouse gases into the atmosphere, which has changed the earth’s climate. Increasing concentrations of greenhouse gas in the atmosphere have increased the greenhouse effect and caused the earth’s surface temperature to rise. Burning fossil fuels like coal, oil, and natural gas changes the climate more than any other human activity.

Temperatures are expected to continue rising over the coming century. To better understand and plan for the impacts of climate change, scientists use computer models to project future changes. These models consider interactions between the ocean, atmosphere, and land and how conditions may change under different levels of future greenhouse gas emissions. These calculations help give an idea of the things at risk, how the environment will continue to change, and where best to direct our collective action.

The warmer it gets, the greater the risk for more severe changes to the climate. Although it's difficult to precisely predict the timing and magnitude of future climate changes, many observed climate impacts are expected to be amplified with future warming.

You can click the tiles to learn more about projected future precipitation and heat changes and the impacts associated with those changes.

Extreme heat can threaten lives, disrupt daily activities, and harm agricultural and transportation systems.

Learn more about extreme heat

Extreme Precipitation

Extreme precipitation events can overwhelm infrastructure and threaten people's homes, belongings, and livelihoods.

Learn more about extreme precipitation Future Climate: An Overview

While climate change is happening on a global scale, the impacts are felt locally in our neighborhoods, workplaces, and communities. You can learn more about these impacts in the interactive graphic by clicking the magnifying glasses.

To learn more about climate change impacts, visit the Climate Change Impacts by Sector. To learn more about observed changes, visit Climate Change Indicators.

References

1 Payton, E. A. et al. (2023) Ch. 4: Water. In: Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC. doi:10.7930/NCA5.2023.CH4.

2 West, J. J. et al. (2023) Ch. 14: Air Quality. In: Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC. doi:10.7930/NCA5.2023.CH14.

3 May, C. L. et al. (2023). Ch. 9: Coastal Effects. In: Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC. doi:10.7930/NCA5.2023.CH9.

4 Mills, K. E. et al. (2023) Ch. 10: Ocean Ecosystems and Marine Resources. In: Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC. doi:10.7930/NCA5.2023.CH10.

5 Marvel, K. et al. (2023) Ch. 2: Climate Trends. In: Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC. doi:10.7930/NCA5.2023.CH2.

6 Domke, G. M. et al. (2023) Ch. 7: Forests. In: Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC. doi:10.7930/NCA5.2023.CH7.

7 McElwee, P. D. et al. (2023) Ch. 8: Ecosystems, Ecosystem Services, and Biodiversity. In: Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC. doi:10.7930/NCA5.2023.CH8.

Climate Change Science

Basics Causes Impacts

Future of Climate Change

Extreme Heat

Extreme Precipitation

Frequently Asked Questions

Contact Us About Climate Change Science

Last updated on December 12, 2024

Extreme Heat

On this page:

● How Will Climate Change Affect Extreme Heat Across the United States?

● Impacts of Extreme Heat

● Resources

● References

There are several ways to define extreme heat. It is frequently based on how unusually hot and humid it is for an area.1 While summertime temperatures of 100˚F might be normal for Phoenix, Arizona, they would be considered extreme for Seattle, Washington. Extreme heat can also be based on whether a certain temperature is reached. For example, the following figure counts extremely hot days as days where the temperature equals or exceeds 95˚F.

As average temperatures rise due to climate change, the risk of extreme temperatures, heat waves, and record-breaking temperatures increases. While warming temperatures are expected across the United States, the severity of warming in a given location depends on geographic factors such as latitude, elevation, and proximity to the ocean. Explore the following figure to learn how the number of extremely hot days is projected to change with different global temperature increases.

Interactive Map: Number of Extremely Hot Days Under Different Global Temperature Change Scenarios

The number of extremely hot days, defined as days with temperatures above 95˚F, is projected to increase with climate change. These maps show the projected increase in hot days under two average global warming scenarios: 1.5˚C (2.7˚F) on the left and 3˚C (5.4˚F) on the right. The warming levels correspond with global average temperature increases above pre-industrial levels measured for the period

1851 to 1900. Use the slider to toggle between the two projected scenarios.

Visit the National Climate Assessment Interactive Atlas Explorer for additional projections and details about calculations.

Source: National Climate Assessment Interactive Atlas Explorer

How Will Climate Change Affect Extreme Heat

Across the United States?

● The United States is expected to continue to warm faster than other parts of the world. As average temperatures increase, the risk of extreme heat goes up. Across the contiguous United States, average temperatures have already risen about 60% more than the global average since 1970.2 This is expected to continue as global temperatures rise due to climate change. The northern and western parts of the country are projected to warm even more.3

● Extremely hot days are projected to occur more often. The number of days above 95˚F is expected to increase across the United States.4

● Heat waves are projected to get worse. Multiday heat waves are expected to be longer, affect more of the country, and become more severe.5 In recent decades, heat waves have already become hotter, occur more often, and are larger and longer-lasting.6

● Warm nights are expected to become more common. Many parts of the country are projected to experience more warm nights where temperatures do not drop below 70˚F.7 Elevated nighttime temperatures mean that people and infrastructure do not have a chance to cool down overnight.

Stay Safe During Extreme Heat

Learn more about how to prepare for and stay healthy during extreme heat events.

Impacts of Extreme Heat

Continued warming poses risks to many aspects of life, including:

● Human Health

● Daily Activities

● Agriculture and Food Supply

● Infrastructure and Transportation Systems

Human Health

● Heat is already the leading weather-related cause of death in the United States.8 The risk of heat-related death and illness is expected to increase as extreme heat events become more frequent and intense.9

○ Extreme heat threatens people’s health when the body is unable to cool down. One way to cool down is for sweat to evaporate off a person’s body. When humidity is high, it is harder for sweat to evaporate and keep a person cool. Heat, especially when made worse by humidity, can cause heat exhaustion and heat stroke, which can lead to hospitalization or death.10

○ Heat can worsen pre-existing health conditions. Higher temperatures are associated with an increase in emergency room visits and hospitalizations related to conditions such as cardiovascular diseases, respiratory diseases, and diabetes.11 Heat can also cause adverse pregnancy and birth outcomes.

○ Extreme heat can have negative impacts on mental health and has been linked to increased rates of suicide and interpersonal violence.12

● While anyone can be impacted by extreme heat, certain groups are more at risk than others.13 Hotter summer temperatures will increase that risk.14

○ Children, adults over 65, pregnant people, people with pre-existing medical conditions or who are taking medications, and people with mental health or substance use disorders face a higher risk of heatrelated health impacts.15

○ Heat waves disproportionately impact communities and people who have been marginalized, including people of color and low-income individuals.16 This is in part due to systemic discriminatory development practices, such as redlining. These practices have left some communities with less access to cooling resources and fewer strategies to reduce heat, such as green space and urban trees.17

○ People living in cities, especially in low-income and high-density

neighborhoods, will experience more extreme heat because of the heat island effect.18

● People who work outdoors are more exposed to extreme heat. This can include agriculture, fishing, construction, transportation, utility, or delivery workers.19 Workers in buildings that are not air-conditioned or climate controlled are also at risk.20

●

● Source: USDA

○ Without proper training and monitoring, as well as hydration, breaks, and shade,21 more frequent and intense heat waves could increase health risks for outdoor workers.

○ Farmworkers are more at risk of heat stress and death than other U.S. workers. The number of unsafe working days for farmworkers due to heat is projected to double by the middle of the century.22

Climate Change, Heat, and Health

Learn more about how rising temperatures, extreme heat, and other climate-related health hazards affect at-risk populations, as well as what actions people can take to decrease the health impacts of climate change.

Daily Activities

● Extreme heat will impact schools, recreation, homes, workplaces, and other parts of daily life for children and adults.

○ High temperatures at home or at school can make it harder to learn and are associated with learning losses for children.23 Many schools in

the United States don’t have air conditioning or are in need of system upgrades.24

○ Hotter temperatures can make outdoor recreational activities unsafe, particularly during midday when the sun is at its highest angle and is most intense.

○ Outdoor workers could lose up to 34 labor hours per year per person due to high temperature days with continued climate change.25 They could also face lower or more irregular pay. Across the whole economy, this could contribute to up to $46 billion in lost wages by the middle of the century.26

○ As climate change leads to an increase in unusually hot days, Americans are expected to spend more money on electricity for cooling.27 Energy costs, which can already be a burden to families, may become increasingly unaffordable. Living in older or poorly insulated homes that are not energy-efficient adds to this concern.

Agriculture and Food Supply

● Hotter temperatures are expected to reduce agricultural food supply, disrupt subsistence activities, cause stress to livestock, and impact water availability.

○ Drought and changes to the natural timing of seasonal plant growth lead to decreased crop yields.28

○ Warming temperatures can increase the range of pests and non-native species that can harm crops and livestock.29

○ Some crops, such as corn, wheat, and rice, are predicted to be up to 30 percent more expensive by the middle of the century because of reduced production.30

○ Extreme heat can place strain on livestock and limit their production.31 Dairy cows are particularly sensitive to heat stress, which can reduce how much and the quality of milk they produce.32,33

○ Indigenous people and others who practice foraging, hunting, fishing,

and farming for subsistence, cultural traditions, and medicinal purposes face can be particularly vulnerable to climate impacts.34

Infrastructure and Transportation Systems

● Rising temperatures and extreme heat can damage energy infrastructure and transportation systems, causing safety hazards, increased need for road maintenance, and airport and train delays.35

○ Extreme heat can cause powerlines to sag. This reduces the efficiency of the grid during a time when demand may already be high due to increased use of cooling systems.36

○ Extreme heat can contribute to electricity infrastructure, including transformers and transmission lines, deteriorating more quickly.37

○ Many types of vehicles can overheat due to high temperatures. Tires can also deteriorate more quickly.38

○ Extreme heat can cause roadways, airport runways, and rail lines to expand and buckle, leading to delays and requiring more frequent repairs or speed restrictions.39

Resources

● Fifth National Climate Assessment: Human Health

● Fifth National Climate Assessment: Climate Trends

● Climate Change and Social Vulnerability in the United States

● Climate Change and Children’s Health and Well-Being in the United States

● National Integrated Heat Health Information System Heat.gov

References

1 EPA. (2016). Climate Change and Extreme Heat: What You Can Do to Prepare (PDF). EPA 430-R-16061.

2 Marvel, K., et al. (2023). Ch. 2. Climate trends. In: Fifth National Climate Assessment. U.S. Global

Change Research Program, Washington, DC. https://doi.org/10.7930/NCA5.2023.CH2 p. 2-4.

3 Ibid, p. 2-21.

4 Ibid, p. 2-24.

5 Ibid, p. 2-24.

6 Ibid, p. 2-24.

7 Ibid, p. 2-18.

8 NOAA (National Oceanic and Atmospheric Administration). (2023). Weather related fatality and injury statistics. Retrieved November 26, 2024, from www.weather.gov/hazstat

9 Hayden, M.H., et al. (2023). Ch. 15. Human health. In: Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC. https://doi.org/10.7930/NCA5.2023.CH15 p. 15-6.

10 Sarofim, M. C., Saha, S., Hawkins, M. D., Mills, D. M., Hess, J., Horton, R., Kinney, P., Schwartz, J., & St. Juliana, A. (2016). Chapter 2: Temperature-related death and illness. In USGCRP (U.S. Global Change Research Program), The impacts of climate change on human health in the United States: A scientific assessment (pp. 43–69). http://dx.doi.org/10.7930/J0MG7MDX

11 Hayden, M.H., et al. (2023). Ch. 15. Human health. In: Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC. https://doi.org/10.7930/NCA5.2023.CH15.p. 15-6.

12 Ibid, p. 15-10.

13 Ibid, p. 15-6.

14 EPA. 2021. Climate Change and Social Vulnerability in the United States: A Focus on Six Impacts. U.S. Environmental Protection Agency, EPA 430-R-21-003.

15 Hayden, M.H., et al. (2023). Ch. 15. Human health. In: Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC. https://doi.org/10.7930/NCA5.2023.CH15. p. 15-6.

16 EPA. 2021. Climate Change and Social Vulnerability in the United States: A Focus on Six Impacts. U.S. Environmental Protection Agency, EPA 430-R-21-003.

17 Chu, E.K., et al. (2023). Ch. 12. Built environment, urban systems, and cities. In: Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC. https://doi.org/10.7930/NCA5.2023.CH12. p. 12-13.

Ibid. pp. 12-12-13.

19 Hayden, M.H., et al. (2023). Ch. 15. Human health. In: Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC. https://doi.org/10.7930/NCA5.2023.CH15. p. 15-12.

20 Ibid, p. 15-12.

21 EPA. (2024). Preventing Heat Stress in Agriculture. Retrieved 11/11/2024.

22 Bolster, C.H., et al. (2023). Ch. 11. Agriculture, food systems, and rural communities. In: Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC. https://doi.org/10.7930/NCA5.2023.CH11. p. 11-16.

23 EPA. 2023. Climate Change and Children’s Health and Well-Being in the United States. U.S. Environmental Protection Agency, EPA 430-R-23-001.

24 United States Government Accountability Office. (2020). School Districts Frequently Identified Multiple Building Systems Needing Updates or Replacement. GAO-20-494.

25 EPA. (2021). Climate Change and Social Vulnerability in the United States: A Focus on Six Impacts. U.S. Environmental Protection Agency, EPA 430-R-21-003. p. 39.

26 Hayden, M.H., et al. (2023). Ch. 15. Human health. In: Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC. https://doi.org/10.7930/NCA5.2023.CH15. p. 15-12.

27 EPA. (2024). Climate Change Indicators: Residential Energy Use. Retrieved 11/11/2024.

28 Bolster, C.H., et al. (2023). Ch. 11. Agriculture, food systems, and rural communities. In: Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC. https://doi.org/10.7930/NCA5.2023.CH11. p. 11-4.

29 Ibid. p. 11-24.

30 Ibid. p. 11-17.

31 Wilson, A.B., et al. (2023). Ch. 24. Midwest. In: Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC. https://doi.org/10.7930/NCA5.2023.CH24. p. 24-8.

32 Ibid. p. 24-8.

33 Key, N., Sneeringer, S. and Marquardt, D. (2014). Climate Change, Heat Stress, and U.S. Dairy Production. ERR-175, U.S. Department of Agriculture, Economic Research Service.

34Bolster, C.H., et al. (2023). Ch. 11. Agriculture, food systems, and rural communities. In: Fifth National Climate Assessment. U.S. Global Change Research Program, Washington DC. https://doi.org/10.7930/NCA5.2023.CH11. p. 11-18.

35 Liban, C.B., et al. (2023). Ch. 13. Transportation. In: Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC. https://doi.org/10.7930/NCA5.2023.CH13. p. 13-8.

36 Zamuda, C.D., et al. (2023). Ch. 5. Energy supply, delivery, and demand. In: Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC. https://doi.org/10.7930/NCA5.2023.CH5. p. 5-7.

37 Ibid, p. 5-7.

38Jacobs, J.M, et al. (2018). Ch. 12. Transportation. In: Fourth National Climate Assessment, Volume II U.S. Global Change Research Program, Washington, DC. https://doi.org/10.7930/NCA5.2023.CH12. p. 489.

39 Ibid, p. 489.

Climate Change Science

Basics Causes Impacts Future of Climate Change

Extreme Heat

Extreme Precipitation Frequently Asked Questions

Contact Us About Climate Change Science

Last updated on December 12, 2024

Extreme Precipitation

On this page:

● How Will Climate Change Affect Extreme Precipitation Across the United States?

● Impacts of Extreme Precipitation

● Resources

● References

Extreme precipitation happens when a location receives much more rain or snow during a short period of time than is normal.1 What counts as “extreme” depends on the location and season. For example, some locations might frequently experience two inches of rainfall from a single storm. However, in other places, this amount of rain might be very rare, so it would be considered extreme. In the maps below, extreme precipitation is defined as the top 1% of the heaviest precipitation events for an area given historical records.

Since the 1950s, heavy precipitation events have been happening more often across the contiguous United States, especially in the Northeast and Midwest.2

There is strong evidence that warming due to human activities has contributed to this increase.2 Warmer air temperatures intensify evaporation, which increases the amount of moisture in the air and can fuel more intense precipitation events.1,3

Interactive Map: Number of Days With Extreme Precipitation Under Different Global Temperature Change Scenarios

The number of days with extreme precipitation is projected to increase with climate change in many areas. Extreme precipitation is defined as precipitation equal to or greater than the top 1% of heavy precipitation events occurring between 1915 and 2018. These maps show the projected change in days with extreme precipitation under two average global warming scenarios: 1.5˚C (2.7˚F) on the left and 3˚C

(5.4˚F) on the right. The warming levels correspond with global average temperature increases above pre-industrial levels measured for the period 1851 to 1900. Use the slider to toggle between the two projected scenarios.

Visit the National Climate Assessment Interactive Atlas Explorer for additional projections and details about calculations.

How Will Climate Change Affect Extreme Precipitation Across the United States?

● As the planet warms, extreme precipitation events are expected to happen more often. Even in regions of the country that are expected to receive less precipitation overall, the precipitation that does fall will come in heavier bursts.4 These heavy bursts can lead to more runoff and raise the risk of flooding. 5

● Changes in extreme precipitation vary by season. Extreme precipitation is expected to increase in spring and winter across the contiguous United States and Alaska.6 While some areas of the country are experiencing drier summers, projected changes in the summer are less certain.6

Stay Safe During Floods

Learn more about how to prepare for and stay safe during and after flooding.

Impacts of Extreme Precipitation

Continued warming poses risks to many aspects of life, including:

● Human Health

● Stormwater Infrastructure and Water Quality

● Agriculture

● Transportation, Communication, and Energy Infrastructure

Human Health

● More frequent and intense heavy storms can lead to an increase in flooding events. This is especially the case in urban areas that are covered with buildings and pavement that do not soak up as much water as natural areas.7 Agricultural areas can also be more flood-prone as intensive agriculture can

reduce how much water soils can absorb.7

○ Floodwaters can transport debris, chemicals, bacteria, and other contaminants that are harmful to humans.7 Floodwaters can also contaminate drinking water resources, which can lead to illnesses if the contamination is not removed in treatment.7

○ Flooding can disrupt access to health care by blocking roads and damaging healthcare facilities.8

○ Homes that have flooded are at risk of developing dangerous levels of mold, which can worsen asthma and other respiratory illnesses.9

○ Flooding can result in injuries and deaths, as well as mental health impacts from trauma and displacement.10

● Increases in heavy precipitation events are expected to increase runoff across much of the United States.11 When water cannot be soaked up by the ground and flows over it, it picks up contaminants as it runs over surfaces.

○ On farmlands, large amounts of runoff from heavy rain can cause fertilizer to flow into streams and lakes.7 Once in a body of water, these nutrients feed harmful algal blooms and degrade the quality of water bodies that might be used for drinking water or recreation.7

Climate Change, Precipitation, and Health

Learn more about how extreme precipitation and other climate-related health hazards affect at-risk populations, as well as what steps people can take to decrease the health impacts of climate change.

Stormwater Infrastructure and Water Quality

● Heavy precipitation and flooding can overwhelm stormwater systems and affect water quality.

○ Many cities in the United States have combined sewer systems that carry wastewater and stormwater in the same pipes. Heavy rain can overwhelm these systems and force them to release untreated wastewater into local water bodies.7,12 These combined sewer overflows, containing raw sewage, debris, and other hazardous substances, can pose risks to people and wildlife.

○ Flooding can have disproportionate impacts on infrastructure in underserved communities, creating environmental justice concerns.13 More than 1,000 community water systems in the United States already experience water quality problems and are not well-prepared for flooding from increased extreme precipitation.14 The communities these systems serve are largely composed of older adults and people who are economically disadvantaged, are Indigenous, or have less education.14

Agriculture

● Heavier rainstorms can undermine agricultural production and disrupt farm operations. These impacts can threaten farmers and farm workers’ livelihoods as well as people who depend on the affected food products.

○ Floods can damage crops. Scientists estimate that between 1981 and 2016, high rainfall caused about as much harm to crop yields across the United States as extreme drought did.15

○ Healthy soil is crucial for crops to grow. Heavy precipitation can erode topsoil and wash away its nutrients.16

○ In some areas, farmers have delayed planting because their fields were too wet from heavy spring rains.16,17

○ Changes in the timing and amount of rainfall can reduce the number of days farmworkers can work in the field, impacting livelihoods.18

Transportation, Communication, and Energy Infrastructure Systems

● Heavy precipitation and flooding can damage buildings and infrastructure.

○ Runoff and flooding can block or damage roads, bridges, tunnels, and railways—resulting in disruptions and delays.19

○ Flooding can affect important digital communication and internet infrastructure.20

○ Heavy rain and flooding can disrupt energy supply chains, threaten operations, and damage infrastructure, which can cause power outages.21 Power outages can pose safety risks by disrupting energy to

homes and essential services like health care operations. Power outages can also have major economic implications. By 2090, power interruptions in the United States due to climate change could cost over $8 billion per year.21

○ In the United States, communities of color, certain immigrant communities, people with low income, and people with limited English proficiency are more likely to live in flood-prone areas.13 These communities are also more likely to live in locations with poorly maintained infrastructure, adding to their risk.13 These inequities are due in part to systemic discriminatory development practices.22 For example, communities with higher percentages of Black residents are projected to experience more annual economic damages from flooding. 23

Climate Change Impacts by Sector

Visit EPA’s Climate Change Impacts by Sector web area to learn more about how climate change affects agriculture and food supply, transportation, infrastructure, and other sectors across the United States.

Resources

● Fifth National Climate Assessment: Human Health

● Fifth National Climate Assessment: Climate Trends

● Climate Change and Social Vulnerability in the United States

● Climate Change and Children’s Health and Well-Being in the United States

References

1U.S. EPA. (2024) Climate Change Indicators: Heavy Precipitation. Retrieved 12/11/2024.

2 Marvel, K. et al. (2023) Ch. 2: Climate Trends. Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC. doi:10.7930/NCA5.2023.CH2. p. 2-18.

3 Leung, L. R. et al. (2023) Ch. 3: Earth Systems Processes. Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC. doi:10.7930/NCA5.2023.CH3. p. 3-22.

4 Marvel, K. et al. (2023) Ch. 2: Climate Trends. Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC. doi:10.7930/NCA5.2023.CH2. p. 2-19.

5 Ibid. p. 2-25.

6 Ibid., p. 2-24.

7 Payton, E. A. et al. (2023) Ch. 4: Water. Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC. doi:10.7930/NCA5.2023.CH4. p. 4-17.

8Hayden, M. H. et al. (2023) Ch. 15: Human Health. Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC. doi:10.7930/NCA5.2023.CH15. p. 15-17.

9 EPA. (2023) Climate Change and Children’s Health and Well-Being in the United States. U.S. Environmental Protection Agency, EPA 430-R-23-001. p. 57.

10 EPA. (2023) Climate Change and Children’s Health and Well-Being in the United States. U.S. Environmental Protection Agency, EPA 430-R-23-001. p. 58.

11 Payton, E. A. et al. (2023) Chapter 4: Water. Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC. doi:10.7930/NCA5.2023.CH4. p. 4-11.

12 EPA. (2022) Climate Change Impacts on the Built Environment. Retrieved 12/11/2024.

13 EPA. (2021) Climate Change and Social Vulnerability in the United States: A Focus on Six Impacts. p. 69.

14Payton, E. A. et al. (2023) Chapter 4: Water. Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC. doi:10.7930/NCA5.2023.CH4. p. 4-22.

15 Thornton, P. E. et al. (2023) Ch. 6: Land Cover and Land-Use Change. Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC. doi:10.7930/NCA5.2023.CH6. p. 6-11.

16 Wilson, A. B. et al. (2023) Ch. 24: Midwest. Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC. doi:10.7930/NCA5.2023.CH24. p. 24- 7.

17 Whitehead, J. C. et al. (2023) Ch. 21: Northeast. Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC. doi:10.7930/NCA5.2023.CH21. p. 21-8.

18 Walsh, M. et al. (2020) Climate Indicators for Agriculture. U.S. Department of Agriculture. USDA Technical Bulletin 1953. Washington, DC. https://doi.org/10.25675/10217/210930. p. 8.

19 Liban, C. B. et al. (2023) Ch. 13: Transportation. Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC. doi:10.7930/NCA5.2023.CH13. p. 13-8.

20 Chu, E. K. et al. (2023) Ch. 12: Built Environment, Urban Systems, and Cities. Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC. doi:10.7930/NCA5.2023.CH12. p. 12-12.

21 Zamuda, C. D. et al. (2023) Ch. 5: Energy Supply, Delivery, and Demand. Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC. doi:10.7930/NCA5.2023.CH5. p. 5-6.

22 Chu, E. K. et al. (2023) Ch. 12: Built Environment, Urban Systems, and Cities. Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC. doi:10.7930/NCA5.2023.CH12. p. 12-13.

23 Payton, E. A. et al. (2023) Chapter 4: Water. Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC. doi:10.7930/NCA5.2023.CH4. p. 4-20.

Climate Change Science

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Frequently Asked Questions

Contact Us About Climate Change Science Last updated on December 12, 2024

Frequently Asked Questions About Climate Change

This page includes answers to some frequently asked questions about climate change. For information about evidence of climate change, the greenhouse effect, and the human role in climate change, please see EPA Climate Science

On this page:

● Terms

○ What is climate change?

○ What is the difference between weather and climate?

○ What is the difference between global warming and climate change?

○ What is the difference between climate change and climate variability?

● Today’s Climate Change

○ Is there scientific consensus that human activities are causing today’s climate change?

○ Do natural variations in climate contribute to today’s climate change?

○ Is climate change happening in the same way everywhere on the planet?

○ Why has my town experienced record-breaking cold and snowfall if the climate is warming?

● Impacts

○ Why be concerned about a degree or two change in the average global temperature?

○ How does climate change affect people’s health?

○ Who is most at risk from the impacts of climate change?

● Solutions

○ How can people reduce the risks of climate change?

○ What are the benefits of taking action now?

Some of the following links exit the site.

Terms

What is climate change?

Climate change involves significant changes in average conditions—such as temperature, precipitation, wind patterns, and other aspects of climate—that occur over years, decades, centuries, or longer. Climate change involves longer-term trends, such as shifts toward warmer, wetter, or drier conditions. These trends can be caused by natural variability in climate over time, as well as human activities that add greenhouse gases to the atmosphere like burning fossil fuels for energy.

What is the difference between weather and climate?

"Weather" refers to the day-to-day state of the atmosphere such as the combination of temperature, humidity, rainfall, wind, and other factors. "Climate" describes the weather of a place averaged over a period of time, often 30 years or more.

The difference between weather and climate is largely defined by time and geography. Weather refers to the conditions of the atmosphere over a short period of time and typically for a local area. Climate refers to the behavior of the atmosphere over a longer period of time, and usually for a large area. Scientists can compare recent and long-term observations of the climate to detect the influence of greenhouse gases on climate conditions.

What is the difference between global warming and climate change?

The terms "global warming" and "climate change" are sometimes used interchangeably, but global warming is just one of the ways in which climate is affected by rising concentrations of greenhouse gases. "Global warming" describes the recent rise in the global average temperature near the earth's surface, which is caused mostly by increasing concentrations of greenhouse gases (such as carbon dioxide and methane) in the atmosphere from human activities such as burning fossil fuels for energy.

What is the difference between climate change and climate variability?

Climate change occurs over a long period of time, typically over decades or longer. In contrast, climate variability includes changes that occur within shorter timeframes, such as a month, season, or year. Climate variability explains the natural variability within the system. For example, one unusually cold or wet year followed by an unusually warm or dry year would not be considered a sign of climate change.

Today’s Climate Change

Is there scientific consensus that human activities are causing today’s climate change?

Yes. Climate scientists overwhelmingly agree that human activities are responsible for today’s climate change, primarily by releasing excess greenhouse gases into the atmosphere. These greenhouse gas emissions come from activities such as burning fossil fuels for energy, raising livestock, and clearing forests. The Intergovernmental Panel on Climate Change's (IPCC) Sixth Assessment Report, which represents the

work of hundreds of leading experts in climate science, states that "it is unequivocal that human influence has warmed the atmosphere, ocean and land. Widespread and rapid changes in the atmosphere, ocean, cryosphere, and biosphere have occurred.”1

The Fifth National Climate Assessment, developed by the U.S. Global Change Research Program—which is composed of 15 federal scientific agencies— concluded that scientific evidence consistently points to human activities, rather than natural climate trends, as the “only credible explanation” for the average temperature increase of nearly 2°F since the late 1800s.2

“Human activities have unequivocally caused the global warming observed over the industrial era, altering the intensity, frequency, and duration of many weather and climate extremes, including extreme heat, extreme precipitation and flooding, drought, and wildfire.”

Fifth National Climate Assessment, Chapter 3. Earth Systems Processes 3

Hundreds of independent and governmental scientific organizations have released similar statements, both in the United States and worldwide, including the World Meteorological Organization, the American Meteorological Society, and the American Geophysical Union

Human and natural factors both influence the earth’s climate, but the long-term trend observed over the past century can only be explained by the effect of human activities on climate. Source: U.S. Global Change Research Program, Fourth National Climate Assessment, Chapter 2: Our Changing Climate, 2018.

Do natural variations in climate contribute to today’s climate change?

The earth does go through natural cycles of warming and cooling caused by factors such as changes in the sun or volcanic activity. For example, there were times in the distant past when the earth was warmer than it is now. However, natural variations in climate do not explain today’s climate change. Most of the warming since 1950 has been caused by human emissions of greenhouse gases that come from a variety of activities, including burning fossil fuels.

Is climate change happening in the same way everywhere on the planet?

Although climate change is often referred to in global terms, different geographic regions are experiencing climate change in different ways. For example, some places, like the Arctic, are experiencing warming more rapidly than the rest of the world.4

Differences such as these are related to natural climate variations, which can occur because of differences in factors such as topography, ocean currents, and latitude. Differences in land use can also affect regional changes in climate. For example, urbanization and deforestation have both shown to exacerbate increasing temperatures.5

Why has my town experienced record-breaking cold and snowfall if the climate is warming?

Even though the planet is experiencing an overall average warming, some areas may be experiencing extra cold or snowy winters. These cold spells are due to variability in local weather patterns, which sometimes lead to colder-than-average seasons or even colder-than-average years at the local or regional level. In fact, a warmer climate allows for more water vapor in the air, which may lead to extra snowy winters in some areas. As long as it is still cold enough to snow, a warming climate can lead to bigger snowstorms.

Impacts

Why be concerned about a degree or two change in the average global temperature?

The global average temperature has increased about 1.7°F since 1970. During this same period, temperatures have risen around 2.5°F in the contiguous United States and 4.2°F in Alaska.6 Globally, 2023 was the warmest year on record. The period 2014–2023 was the warmest decade on record since thermometer-based observations began.7

A degree or two change in average global temperature might not sound like much to worry about, but relatively small changes in the earth’s average temperature can mean big changes (pdf) in local and regional climate, creating risks to public health and safety, water resources, agriculture, infrastructure, and ecosystems

Among the many examples of changes cited by the Fifth National Climate Assessment are:

● An increase in heat waves and days with temperatures above 90°F

● More extreme weather events such as storms, droughts, and floods

● An increase in wildfires and longer wildfire seasons

● A projected sea level rise of 1 to 4 feet by the end of this century, which could put certain areas of the country underwater

● Melting sea ice and thawing permafrost in the Arctic

● An increase in heat stress on ecosystems, agriculture, and livestock, resulting in biodiversity loss, habitat shifts, and food supply disruptions

● Power grid strain through increased electrical demand for cooling

● Infrastructure damage such as buckling bridges, roads, and railways

How does climate change affect people’s health?

Climate change poses many threats to people’s health and well-being. Among the health impacts cited by the Fifth National Climate Assessment are the following:

● Atmospheric warming has the potential to increase ground-level ozone in many regions, which can cause multiple health issues (e.g., bronchitis, emphysema, and asthma) and worsen lung function.

● Higher summer temperatures are linked to an increased risk of heat-related illnesses and death. Older adults, pregnant women, and children are at particular risk, as are people living in urban areas because of the additional heat associated with urban heat islands.

● Climate change is expected to expand the range and activity of ticks that carry Lyme disease or other bacterial and viral agents, as well as mosquitoes that transmit West Nile and other viruses, which can increase exposure for more people.

● More frequent extreme weather events such as droughts, hurricanes, floods, and wildfires will not only put people’s lives at risk, but can also worsen underlying medical conditions, increase stress, and lead to adverse mental health effects.

● Rising temperatures and extreme weather have the potential to disrupt the availability, safety, and nutritional quality of food.

See EPA’s Climate Indicators website for more information about the effects of climate change in the United States.

Who is most at risk from the impacts of climate change?

Everyone will be affected by climate change, but some people may be more affected than others. Among the most vulnerable people are those in overburdened, underserved, and economically distressed communities. Three key factors influence

a person’s vulnerability to the impacts of climate change:

● Exposure. Some people are more at risk simply because they are more exposed to climate change hazards where they live or work. For example, people who live on the coast can be more vulnerable to sea level rise, coastal storms, and flooding.

● Sensitivity. Some people are more sensitive to the impacts of climate change, such as children, pregnant women, and those with pre-existing medical conditions such as asthma.

● Adaptability. Older adults, those with disabilities, those with low income, and some Indigenous people may have more difficulty than others in adapting to climate change hazards.

In addition, there is a wide range of other factors that influence people’s vulnerability. For example, people with less access to healthcare, adequate housing, and financial resources are less likely to rebound from climate disasters. People who are excluded from planning processes, experience racial and ethnic discrimination, or have language barriers are also more vulnerable to and less able to prepare for and avoid the risks of climate change.

Learn more about the connections between climate change and human health

Solutions

How can people reduce the risks of climate change?

Reducing risk involves both mitigation and adaptation.

● Climate change mitigation refers to actions limiting the magnitude and rate of future climate change by reducing greenhouse gas emissions and/or advancing nature-based solutions.

● Climate change adaptation or climate adaptation means taking action to prepare for and adjust to both the current and projected impacts of climate change.

People can reduce the risks of climate change by making choices that reduce greenhouse gas emissions and by preparing for the changes expected in the future. Decisions that people make today will shape the world for decades and even centuries to come. Communities can also prepare for the changes in the decades ahead by identifying and reducing their vulnerabilities and considering climate change risks in planning and development. Such actions can ensure that the most vulnerable populations—such as young children, older adults, and people living in poverty—are protected from the health and safety threats of climate change.

What are the benefits of taking action now?

The longer people wait to act on climate change, the more damaging its effects will become on the planet and people’s health. If people fail to take action soon, more drastic and costly measures to prevent greenhouse gases from exceeding dangerous levels could be needed later. The Fifth National Climate Assessment found that global efforts to reduce greenhouse gas emissions could avoid tens of thousands of deaths per year in the United States by the end of the century, as well as billions of dollars in damages related to water shortages, wildfires, agricultural losses, flooding, and other impacts.

“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.”

Fifth National Climate Assessment, Overview 8

There are many actions that people can take now to help reduce the risk of climate change while also improving the natural environment, community infrastructure and transportation systems, and overall health.

Climate change presents many risks across the country. Action to limit warming and reduce risks creates benefits and opportunities for the United States. Source: U.S.

Global Change Research Program, Fifth National Climate Assessment, Chapter 1: Overview, 2023.

References

1 IPCC, 2021: Summary for Policymakers. In: Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_SPM.pdf (pdf) p. 4

2 Marvel, K., W. Su, R. Delgado, S. Aarons, A. Chatterjee, M.E. Garcia, Z. Hausfather, K. Hayhoe, D.A. Hence, E.B. Jewett, A. Robel, D. Singh, A. Tripati, and R.S. Vose, 2023: Ch. 2. Climate trends. 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.CH2, p. 2-4.

3 Leung, L.R., A. Terando, R. Joseph, G. Tselioudis, L.M. Bruhwiler, B. Cook, C. Deser, A. Hall, B.D. Hamlington, A. Hoell, F.M. Hoffman, S. Klein, V. Naik, A.G. Pendergrass, C. Tebaldi, P.A. Ullrich, and M.F. Wehner, 2023: Ch. 3. Earth systems processes. 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.CH3

4 Constable et al. (2022). Cross-Chapter Paper 6: Polar Regions. In: Climate Change 2022: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [H.-O. Pörtner, D.C. Roberts, M. Tignor, E.S. Poloczanska, K. Mintenbeck, A. Alegría, M. Craig, S. Langsdorf, S. Löschke, V. Möller, A. Okem, B. Rama (eds.)]. Cambridge University Press, Cambridge, UK and New York, NY, USA, pp. 2319–2368, doi:10.1017/9781009325844.023.

5 IPCC. (2019). Summary for Policymakers. In: Climate Change and Land: an IPCC special report on climate change, desertification, land degradation, sustainable land management, food security, and greenhouse gas fluxes in terrestrial ecosystems [P.R. Shukla, J. Skea, E. Calvo Buendia, V. MassonDelmotte, H.- O. Pörtner, D. C. Roberts, P. Zhai, R. Slade, S. Connors, R. van Diemen, M. Ferrat, E. Haughey, S. Luz, S. Neogi, M. Pathak, J. Petzold, J. Portugal Pereira, P. Vyas, E. Huntley, K. Kissick, M. Belkacemi, J. Malley, (eds.)].

6 Marvel, K., W. Su, R. Delgado, S. Aarons, A. Chatterjee, M.E. Garcia, Z. Hausfather, K. Hayhoe, D.A. Hence, E.B. Jewett, A. Robel, D. Singh, A. Tripati, and R.S. Vose, 2023: Ch. 2. Climate trends. 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.CH2, p. 2-11.

7 EPA (2024). Climate Change Indicators: U.S. and Global Temperature. Accessed November 20, 2024 https://www.epa.gov/climate-indicators/climate-change-indicators-us-and-global-temperature

8 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, p. 1-37.

Climate Change Science

Basics

Causes Impacts

Future of Climate Change

Frequently Asked Questions

Contact Us About Climate Change Science

Last updated on December 20, 2024