Why are northern wildfires releasing more carbon?

Hidden carbon from smouldering soils

Recent reconstructions of wildfire emissions in boreal and subarctic regions point to a significant blind spot in current climate accounting: deep, organic soils — peat, permafrost layers and thick organic horizons — can smoulder for long periods during and after flames pass, releasing large quantities of ancient carbon that standard fire emissions estimates often miss.

Field and satellite‑based analyses of recent Swedish and Arctic blazes show that combustion of surface vegetation underestimates total carbon loss when smouldering combustion in organic soils is not fully captured. Smouldering occurs at lower temperatures than flaming combustion but can persist for days to months, penetrating deep into peat and thawed permafrost and mobilizing carbon that has been stored for centuries or millennia.

Why this changes the picture

• Emissions underestimates: climate inventories and many models typically focus on the fast, flaming phase and can undercount prolonged smouldering emissions.
• Carbon‑budget implications: extra emissions from smouldering reduce the remaining carbon budget for meeting climate goals and can alter regional greenhouse‑gas trajectories.
• Feedbacks with climate: soil combustion can expose and oxidize previously frozen carbon pools, accelerating warming and increasing future fire risk.

What scientists recommend next

1. Improve detection of smouldering using combined ground measurements and remote sensing.
2. Incorporate prolonged soil combustion into emissions inventories and climate models.
3. Prioritize peatland and permafrost protection and restoration as part of mitigation strategies.

Accounting for this hidden flux is essential to produce accurate projections and to design effective policies for wildfire management and climate mitigation.