Climate impacts from North American boreal forest fires.

Area of Science:

• Climate Science
• Ecology
• Environmental Science

Background:

• Boreal forests are warming rapidly, leading to intensified fire regimes.
• Boreal forest fires have complex impacts on global climate, causing both warming and cooling effects.
• Understanding these impacts is crucial for climate change mitigation.

Purpose of the Study:

• To estimate the net climate impacts of boreal fires in Alaska and western Canada from 2001-2019.
• To analyze the radiative forcing metrics associated with combustion, vegetation recovery, permafrost thaw, and albedo changes.
• To differentiate the drivers of climate warming versus cooling fires.

Main Methods:

• Integrated net radiative forcing metrics were used to combine various climate impact factors.
• Data from Alaska and western Canada between 2001 and 2019 were analyzed.
• Component and net radiative forcing were characterized at a fine scale.

Main Results:

• Fires in Alaska resulted in a net climate warming effect (0.35 ± 4.66 W m⁻²).
• Fires in Canada resulted in a net climate cooling effect (-2.88 ± 4.17 W m⁻²).
• Climate-warming fires were associated with dry, high-elevation permafrost areas with high black spruce cover, while cooling fires were linked to longer spring snow cover.

Conclusions:

• Boreal fires have distinct regional climate impacts, contributing to warming in Alaska and cooling in Canada.
• Fire management in carbon-rich permafrost regions is essential for curbing long-term warming.
• This research advances the understanding of fire's biogeophysical impacts on high-latitude climates.