Canadian wildfires are losing their climate-cooling influence from postfire snow albedo

The 2023 Canadian fire season was record-breaking in terms of burned area and carbon emissions. Here, we present estimates of the regional climate-cooling effect from postfire surface albedo changes, which have historically partially offset the warming influence of fire emissions by wildfires. We estimate that the 2023 fires generated a time-integrated climate cooling of –3.41 W m−2 of burned area (95% CI: −4.39 to −2.43) over a 70-y period. We show that the climate-cooling impact has weakened on average by 29% since the 1960s due to changes in snow cover and duration. Collectively, this result implies that modern-day boreal fires are on average twice as likely to result in a net climate-warming influence.