Impact of anthropogenic climate change on wildfire
across western US forests
John T. Abatzogloua,1 and A. Park Williams b
a Department of Geography, University of Idaho, Moscow, ID 83844; and b Lamont–Doherty Earth Observatory, Columbia University, Palisades, NY 10964
Edited by Monica G. Turner, University of Wisconsin–Madison, Madison, WI, and approved July 28, 2016 (received for review May 5, 2016)
Increased forest fire activity across the western continental United
States (US) in recent decades has likely been enabled by a number of
factors, including the legacy of fire suppression and human settle-
ment, natural climate variability, and human-caused climate change.
We use modeled climate projections to estimate the contribution
of anthropogenic climate change to observed increases in eight fuel
aridity metrics and forest fire area across the western United States.
Anthropogenic increases in temperature and vapor pressure deficit
significantly enhanced fuel aridity across western US forests over the
past several decades and, during 2000–2015, contributed to 75%
more forested area experiencing high (>1 σ) fire-season fuel aridity
and an average of nine additional days per year of high fire potential.
Anthropogenic climate change accounted for ∼55% of observed in-
creases in fuel aridity from 1979 to 2015 across western US forests,
highlighting both anthropogenic climate change and natural climate
variability as important contributors to increased wildfire potential in
recent decades. We estimate that human-caused climate change con-
tributed to an additional 4.2 million ha of forest fire area during 1984–
2015, nearly doubling the forest fire area expected in its absence.
Natural climate variability will continue to alternate between modulat-
ing and compounding anthropogenic increases in fuel aridity, but an-
thropogenic climate change has emerged as a driver of increased forest
fire activity and should continue to do so while fuels are not limiting.
across western US forests
John T. Abatzogloua,1 and A. Park Williams b
a Department of Geography, University of Idaho, Moscow, ID 83844; and b Lamont–Doherty Earth Observatory, Columbia University, Palisades, NY 10964
Edited by Monica G. Turner, University of Wisconsin–Madison, Madison, WI, and approved July 28, 2016 (received for review May 5, 2016)
Increased forest fire activity across the western continental United
States (US) in recent decades has likely been enabled by a number of
factors, including the legacy of fire suppression and human settle-
ment, natural climate variability, and human-caused climate change.
We use modeled climate projections to estimate the contribution
of anthropogenic climate change to observed increases in eight fuel
aridity metrics and forest fire area across the western United States.
Anthropogenic increases in temperature and vapor pressure deficit
significantly enhanced fuel aridity across western US forests over the
past several decades and, during 2000–2015, contributed to 75%
more forested area experiencing high (>1 σ) fire-season fuel aridity
and an average of nine additional days per year of high fire potential.
Anthropogenic climate change accounted for ∼55% of observed in-
creases in fuel aridity from 1979 to 2015 across western US forests,
highlighting both anthropogenic climate change and natural climate
variability as important contributors to increased wildfire potential in
recent decades. We estimate that human-caused climate change con-
tributed to an additional 4.2 million ha of forest fire area during 1984–
2015, nearly doubling the forest fire area expected in its absence.
Natural climate variability will continue to alternate between modulat-
ing and compounding anthropogenic increases in fuel aridity, but an-
thropogenic climate change has emerged as a driver of increased forest
fire activity and should continue to do so while fuels are not limiting.
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