Sensitivity of carbon budgets to permafrost carbon feedbacks, non-CO2 forcings, and negative emissions ...

• Main Authors: MacDougall, Andrew H., Zickfeld, Kirsten, Knutti, Reto, Matthews, H. Damon
• Format: Article in Journal/Newspaper
• Language: English
• Published: ETH Zurich 2015
• Subjects: Carbon budget; TCRE; Climate change; permafrost
• Online Access: https://dx.doi.org/10.3929/ethz-b-000108054; http://hdl.handle.net/20.500.11850/108054

The near proportionality between cumulative CO2 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-CO2 forcings. The carbon budget for 2.0 ${}^{\circ }{\rm{C}}$ of warming is reduced from 1320 Pg C when considering only forcing from CO2 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 CO2 emissions at the point in time a warming target is restored following artificial removal of CO2 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 ... : Environmental Research Letters, 10 (12) ...