What it is
The authors extended a compact Earth system model (OSCAR v3.0) to include abrupt permafrost thaw and wildfire carbon combustion, feedbacks that global-scale permafrost models usually leave out in favor of gradual top-down thaw. Adding these processes cuts the remaining allowable carbon budget from 2025 onward by 25% plus or minus 12% for staying below 1.5 C and by 17% plus or minus 7% for staying below 2.0 C. In absolute terms that is roughly 124 plus or minus 62 GtCO2 less headroom for the 1.5 C goal.
Why it matters
The permafrost carbon feedback has long been feared but poorly quantified, so it rarely enters the budgets that set national emissions targets. This work attaches a concrete, budget-level number to it and to intensifying Arctic fire, showing they materially erode the space left under the Paris goals. A 25% plus or minus 12% cut to the 1.5 C budget means targets calibrated without these feedbacks are systematically too generous.
Underlined numbers link to their source. Every metric and quoted figure is listed under Sources and data below.
Filed underclimate, permafrost, carbon budget, Paris Agreement, wildfire