Carbon Emissions from Permafrost
Limiting warming to 1.5° rather than 2°C saves 2 million square kilometers of permafrost. Permafrost carbon release (as both methane and CO2) is greater at 2°, especially in “overshoot” scenarios because once thawed, former permafrost irreversibly continues to release carbon for centuries:
• If we can hold temperatures to 1.5°C, cumulative permafrost emissions by 2100 will be about equivalent to those currently from Canada (150–200 Gt CO2-eq).
• In contrast, by 2°C scientists expect cumulative permafrost emissions as large as those of the EU (220–300 Gt CO2-eq).
• If temperature exceeds 4°C by the end of the century however, permafrost emissions by 2100 will be as large as those today from major emitters like the United States or China (400–500 Gt CO2-eq), the same scale as the remaining 1.5° carbon budget.
These permafrost carbon estimates include emissions from the newly-recognized abrupt thaw processes from “thermokarst” lakes and hillsides, which expose deeper frozen carbon previously considered immune from thawing for many more centuries.
The “anthropogenic” carbon budget to reach carbon neutrality and remain within 1.5° of warming must begin to take these “country of Permafrost” emissions into account. Only lower emissions pathways that preserve as much permafrost as possible can minimize this potentially large contribution to future global warming, and the need for future generations to maintain negative emissions efforts to compensate for those from thawed former permafrost.