Climate-cooling impacts from post-fire snow-albedo for the 2023 Canadian fires season

The 2023 Canadian fire season was record-breaking in terms of burned area and carbon emissions.  Yet, the climate impacts of these fires extend far beyond the immediate carbon emissions and can persist for decades. Post-fire changes in vegetation and surface properties prolong snow exposure during winter and spring, increasing surface albedo and producing long-lasting regional cooling impacts. Historically, the surface albedo-driven cooling has offset the warming influences of carbon emissions by boreal fires. However, with ongoing high-latitude warming, fire seasons are expected to become longer and more intense while spring snow cover declines. This combination may weaken the climate-cooling effect of post-fire surface-albedo changes and reduce the offset potential.

Here, we quantified and mapped the climate-cooling effects from post-fire surface albedo changes for the 2023 Canadian fire season under shared socioeconomic pathway SSP2-4.5 for a 70-year period. We estimate that the 2023 Canadian fires resulted in a time-integrated climate-cooling of –3.67 W m^-2 of burned area (95% CI: −4.83 to −2.51) over a 70-year period. Our analysis further shows that the climate-cooling impact of boreal fires has weakened by approximately 30% due to changes in snow cover and duration. This has significant implications for the ability of albedo-driven cooling to offset warming from fire emissions. As a result, we conclude that contemporary boreal fires are, on average, twice as likely to result in a net climate-warming effect relative to the 1960s.