Is Climate Change Influencing Wildfires? Climate Change Effects on Wildfires in the United States
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INSIGHTi
Is Climate Change Influencing Wildfires?
Climate Change Effects on Wildfires in the
United States
December 15, 2023
According to the National Oceanic and Atmospheric Administration (NOAA), climate change-driven
increases in temperature, drought, and atmospheric drying have led to an increase in wildfire risk and
wildfire burned area in the western United States. It is the assessment of the U.S. Forest Service (FS) that
fire area and fire-caused tree mortality will increase under future climate change conditions. This Insight
describes changes in wildfire activity in the United States in recent decades and the potential influence of
climate change on wildfires under current and projected climate change conditions.
Recent Decades of Wildfire Activity in the United States
Wildfire extent and damage have been growing in the United States since 1983, when federal agencies
first implemented current wildland fire reporting processes. Wildland fire statistics from the National
Interagency Coordination Center indicate that the number of annual wildfires in the United States is
variable but has decreased moderately from 1993 to 2022, while the number of acres burned annually,
while also variable, has approximately doubled (Figure 1).
The U.S. Global Change Research Program (USGCRP) in the 2017 science volume of the Fourth
National Climate Assessment, using a definition of a large fire as greater than 1,000 acres, reported that
“The incidence of large forest fires in the western United States and Alaska has increased since the early
1980s (high confidence).” The 2018 volume of the assessment, which covers impacts and risks, states
“increasing wildfire is damaging ranches and rangelands as well as property in cities near the wildland–
urban interface.”
Congressional Research Service
https://crsreports.congress.gov
IN12288
CRS INSIGHT
Prepared for Members and
Committees of Congress
Congressional Research Service
2
Figure 1. Annual Wildfires and Acres Burned, 1993-2022
Sources: CRS In Focus IF10244, Wildfire Statistics. Data from National Interagency Coordination Center, Wildland Fire
Summary and Statistics annual reports.
Note: Data reflect wildland fires and acres burned nationwide, including wildland fires on federal and nonfederal lands.
Climate Change Influence on Wildfire
Climate change attribution studies of wildfires seek to quantify and distinguish the influence of human-
caused climate change on wildfires from other influences. In the case of wildfires, these other factors may
include historic fire suppression that may have increased fuel load, changes in settlement at the wildland
urban interface (WUI), and natural climate variability.
Several recent climate change attribution studies suggest that human-caused climate change, independent
of other factors, has increased the risk and the extent of wildfire. For example, in 2018, the USGCRP
cited an attribution analysis that presents evidence that climate change has been increasing conditions
favoring wildfires and the extent of wildfires in some areas of the United States. This analysis found that
climate change has driven increases in temperature and atmospheric drying. The resulting drying of
wildfire fuels across western U.S. forests during the 2000-2015 period contributed to an average of nine
additional days per year of high fire potential relative to a 1981-2000 baseline period. The authors of the
analysis also concluded that during the 1984-2015 period, these climate drivers had approximately
doubled the area of forest burned in the western United States. In another example, a 2023 attribution
study in the Proceedings of the National Academy of Science found that climate change had driven
increases in temperature and atmospheric drying of wildfire fuels in California. The authors concluded
that almost all of the fivefold increase in the area burned by wildfires in California from 1996 to 2021
compared with 1971-1995 could be attributed to human-caused climate change.
Some modeling studies of future climate change have projected increases in wildfire effects on forests in
the United States. In 2020, the FS used climate models to assess the effects of climate change on U.S.
forests. This assessment found that increases in fire area and fire-caused tree mortality were expected
under future conditions of climate change in all parts of the conterminous United States. A later FS
modeling study was included as part of the research basis of the 2022 Office of Management and Budget
white paper on the federal government’s financial risk exposure to climate change. That FS modeling also
found that the area burned by wildfires in the United States is projected to increase under conditions of
human-caused climate change. The influence of climate change on wildfire is unlikely to be uniform, as
Congressional Research Service
3
the USGCRP found that “[i]ncreases in future forest fire extent, frequency, and intensity depend strongly
on local ecosystem properties and will vary greatly across the United States.”
Considerations for Congress
According to the FS 10-year wildfire implementation plan published in 2022, the increase in the size and
severity of wildfires has placed “homes, communities, infrastructure, and natural resources at grave and
growing risk,” with wide-ranging impacts to local economies and communities, human wellbeing, and the
environment. As such, wildfire could affect broad areas of federal activity, including several federal roles
related specifically to wildfire. Agencies that manage federal lands are responsible for wildfire
management on those lands, including fire suppression, post-fire recovery, and managing the land for
wildfire (as it comports with the agency’s mission), including reducing its likelihood and severity. The
federal government also may provide assistance for wildfire suppression and preparedness on nonfederal
land. Lastly, the federal government may provide a variety of post-fire disaster assistance to individuals,
businesses, communities, and other groups.
Potential climate change-induced increases in future wildfire frequency and burned area, as well as other
factors such as forest and fuels management and development in the WUI, could affect these federal
activities in a variety of ways. For example, increases in burned area could increase the number of people
and communities affected, potentially increasing demand for federal disaster relief and suppression
resources. Some federal spending related to wildfire has increased in recent decades—for example,
appropriations for wildfire management increased from 2011 to 2020. Most of this increase was
attributable to wildfire suppression spending. Changes in wildfire risk and extent could shape a wide
range of congressional debates, from the appropriate level and distribution of wildfire-related federal
spending to the management of federal lands to the federal role in disaster response. These changes also
could inform debates regarding the federal response to climate change.
Author Information
Jonathan D. Haskett
Anne A. Riddle
Analyst in Environmental Policy
Analyst in Natural Resources Policy
Disclaimer
This document was prepared by the Congressional Research Service (CRS). CRS serves as nonpartisan shared staff
to congressional committees and Members of Congress. It operates solely at the behest of and under the direction of
Congress. Information in a CRS Report should not be relied upon for purposes other than public understanding of
information that has been provided by CRS to Members of Congress in connection with CRS’s institutional role.
CRS Reports, as a work of the United States Government, are not subject to copyright protection in the United
States. Any CRS Report may be reproduced and distributed in its entirety without permission from CRS. However,
as a CRS Report may include copyrighted images or material from a third party, you may need to obtain the
permission of the copyright holder if you wish to copy or otherwise use copyrighted material.
IN12288 · VERSION 1 · NEW
INSIGHTi
Is Climate Change Influencing Wildfires?
Climate Change Effects on Wildfires in the
United States
December 15, 2023
According to the National Oceanic and Atmospheric Administration (NOAA), climate change-driven
increases in temperature, drought, and atmospheric drying have led to an increase in wildfire risk and
wildfire burned area in the western United States. It is the assessment of the U.S. Forest Service (FS) that
fire area and fire-caused tree mortality will increase under future climate change conditions. This Insight
describes changes in wildfire activity in the United States in recent decades and the potential influence of
climate change on wildfires under current and projected climate change conditions.
Recent Decades of Wildfire Activity in the United States
Wildfire extent and damage have been growing in the United States since 1983, when federal agencies
first implemented current wildland fire reporting processes. Wildland fire statistics from the National
Interagency Coordination Center indicate that the number of annual wildfires in the United States is
variable but has decreased moderately from 1993 to 2022, while the number of acres burned annually,
while also variable, has approximately doubled (Figure 1).
The U.S. Global Change Research Program (USGCRP) in the 2017 science volume of the Fourth
National Climate Assessment, using a definition of a large fire as greater than 1,000 acres, reported that
“The incidence of large forest fires in the western United States and Alaska has increased since the early
1980s (high confidence).” The 2018 volume of the assessment, which covers impacts and risks, states
“increasing wildfire is damaging ranches and rangelands as well as property in cities near the wildland–
urban interface.”
Congressional Research Service
https://crsreports.congress.gov
IN12288
CRS INSIGHT
Prepared for Members and
Committees of Congress
Congressional Research Service
2
Figure 1. Annual Wildfires and Acres Burned, 1993-2022
Sources: CRS In Focus IF10244, Wildfire Statistics. Data from National Interagency Coordination Center, Wildland Fire
Summary and Statistics annual reports.
Note: Data reflect wildland fires and acres burned nationwide, including wildland fires on federal and nonfederal lands.
Climate Change Influence on Wildfire
Climate change attribution studies of wildfires seek to quantify and distinguish the influence of human-
caused climate change on wildfires from other influences. In the case of wildfires, these other factors may
include historic fire suppression that may have increased fuel load, changes in settlement at the wildland
urban interface (WUI), and natural climate variability.
Several recent climate change attribution studies suggest that human-caused climate change, independent
of other factors, has increased the risk and the extent of wildfire. For example, in 2018, the USGCRP
cited an attribution analysis that presents evidence that climate change has been increasing conditions
favoring wildfires and the extent of wildfires in some areas of the United States. This analysis found that
climate change has driven increases in temperature and atmospheric drying. The resulting drying of
wildfire fuels across western U.S. forests during the 2000-2015 period contributed to an average of nine
additional days per year of high fire potential relative to a 1981-2000 baseline period. The authors of the
analysis also concluded that during the 1984-2015 period, these climate drivers had approximately
doubled the area of forest burned in the western United States. In another example, a 2023 attribution
study in the Proceedings of the National Academy of Science found that climate change had driven
increases in temperature and atmospheric drying of wildfire fuels in California. The authors concluded
that almost all of the fivefold increase in the area burned by wildfires in California from 1996 to 2021
compared with 1971-1995 could be attributed to human-caused climate change.
Some modeling studies of future climate change have projected increases in wildfire effects on forests in
the United States. In 2020, the FS used climate models to assess the effects of climate change on U.S.
forests. This assessment found that increases in fire area and fire-caused tree mortality were expected
under future conditions of climate change in all parts of the conterminous United States. A later FS
modeling study was included as part of the research basis of the 2022 Office of Management and Budget
white paper on the federal government’s financial risk exposure to climate change. That FS modeling also
found that the area burned by wildfires in the United States is projected to increase under conditions of
human-caused climate change. The influence of climate change on wildfire is unlikely to be uniform, as
Congressional Research Service
3
the USGCRP found that “[i]ncreases in future forest fire extent, frequency, and intensity depend strongly
on local ecosystem properties and will vary greatly across the United States.”
Considerations for Congress
According to the FS 10-year wildfire implementation plan published in 2022, the increase in the size and
severity of wildfires has placed “homes, communities, infrastructure, and natural resources at grave and
growing risk,” with wide-ranging impacts to local economies and communities, human wellbeing, and the
environment. As such, wildfire could affect broad areas of federal activity, including several federal roles
related specifically to wildfire. Agencies that manage federal lands are responsible for wildfire
management on those lands, including fire suppression, post-fire recovery, and managing the land for
wildfire (as it comports with the agency’s mission), including reducing its likelihood and severity. The
federal government also may provide assistance for wildfire suppression and preparedness on nonfederal
land. Lastly, the federal government may provide a variety of post-fire disaster assistance to individuals,
businesses, communities, and other groups.
Potential climate change-induced increases in future wildfire frequency and burned area, as well as other
factors such as forest and fuels management and development in the WUI, could affect these federal
activities in a variety of ways. For example, increases in burned area could increase the number of people
and communities affected, potentially increasing demand for federal disaster relief and suppression
resources. Some federal spending related to wildfire has increased in recent decades—for example,
appropriations for wildfire management increased from 2011 to 2020. Most of this increase was
attributable to wildfire suppression spending. Changes in wildfire risk and extent could shape a wide
range of congressional debates, from the appropriate level and distribution of wildfire-related federal
spending to the management of federal lands to the federal role in disaster response. These changes also
could inform debates regarding the federal response to climate change.
Author Information
Jonathan D. Haskett
Anne A. Riddle
Analyst in Environmental Policy
Analyst in Natural Resources Policy
Disclaimer
This document was prepared by the Congressional Research Service (CRS). CRS serves as nonpartisan shared staff
to congressional committees and Members of Congress. It operates solely at the behest of and under the direction of
Congress. Information in a CRS Report should not be relied upon for purposes other than public understanding of
information that has been provided by CRS to Members of Congress in connection with CRS’s institutional role.
CRS Reports, as a work of the United States Government, are not subject to copyright protection in the United
States. Any CRS Report may be reproduced and distributed in its entirety without permission from CRS. However,
as a CRS Report may include copyrighted images or material from a third party, you may need to obtain the
permission of the copyright holder if you wish to copy or otherwise use copyrighted material.
IN12288 · VERSION 1 · NEW