Sensitivity of carbon budgets to permafrost carbon feedbacks and non-CO2 forcings

• Published in: Environmental Research Letters
• Main Authors: Andrew H MacDougall, Kirsten Zickfeld, Reto Knutti, H Damon Matthews
• Format: Article in Journal/Newspaper
• Language: English
• Published: IOP Publishing 2015
• Subjects: carbon budget; TCRE; climate change; Environmental technology. Sanitary engineering; TD1-1066; Environmental sciences; GE1-350; Science; Q; Physics; QC1-999; permafrost
• Online Access: https://doi.org/10.1088/1748-9326/10/12/125003; https://doaj.org/article/14d5354928e040889d3ad4bb2d198588

The near proportionality between cumulative CO _2 emissions and change in near surface temperature can be used to define a carbon budget: a finite quantity of carbon that can be burned associated with a chosen ‘safe’ temperature change threshold. Here we evaluate the sensitivity of this carbon budget to permafrost carbon dynamics and changes in non-CO _2 forcings. The carbon budget for 2.0 ${}^{\circ }{\rm{C}}$ of warming is reduced from 1320 Pg C when considering only forcing from CO _2 to 810 Pg C when considering permafrost carbon feedbacks as well as other anthropogenic contributions to climate change. We also examined net carbon budgets following an overshoot of and return to a warming target. That is, the net cumulative CO _2 emissions at the point in time a warming target is restored following artificial removal of CO _2 from the atmosphere to cool the climate back to a chosen temperature target. These overshoot net carbon budgets are consistently smaller than the conventional carbon budgets. Overall carbon budgets persist as a robust and simple conceptual framework to relate the principle cause of climate change to the impacts of climate change.