Quantifying non-CO2 contributions to remaining carbon budgets

Stuart Jenkins (1) , Michelle Cain (2) , Pierre Friedlingstein (3, 4) , Nathan Gillett (5) , Tristram Walsh , Myles Allen (6)

1 AOPP - Department of Atmospheric, Oceanic and Planetary Physics [Oxford]
2 Cranfield University
3 LMD - Laboratoire de Météorologie Dynamique (UMR 8539)
4 IPSL (FR_636) - Institut Pierre-Simon-Laplace
5 CCCma - Canadian Centre for Climate Modelling and Analysis
6 SoGE - School of Geography and the Environment [Oxford]

The IPCC Special Report on 1.5 °C concluded that anthropogenic global warming is determined by cumulative anthropogenic CO 2 emissions and the non-CO 2 radiative forcing level in the decades prior to peak warming. We quantify this using CO 2 -forcing-equivalent (CO 2 -fe) emissions. We produce an observationally constrained estimate of the Transient Climate Response to cumulative carbon Emissions (TCRE), giving a 90% confidence interval of 0.26–0.78 °C/TtCO 2 , implying a remaining total CO 2 -fe budget from 2020 to 1.5 °C of 350–1040 GtCO 2 -fe, where non-CO 2 forcing changes take up 50 to 300 GtCO 2 -fe. Using a central non-CO 2 forcing estimate, the remaining CO 2 budgets are 640, 545, 455 GtCO 2 for a 33, 50 or 66% chance of limiting warming to 1.5 °C. We discuss the impact of GMST revisions and the contribution of non-CO 2 mitigation to remaining budgets, determining that reporting budgets in CO 2 -fe for alternative definitions of GMST, displaying CO 2 and non-CO 2 contributions using a two-dimensional presentation, offers the most transparent approach.

Domaines: Océan, Atmosphère

Stuart Jenkins, Michelle Cain, Pierre Friedlingstein, Nathan Gillett, Tristram Walsh, et al.. Quantifying non-CO2 contributions to remaining carbon budgets. npj climate and atmospheric science, 2021, 4 (1), ⟨10.1038/s41612-021-00203-9⟩. ⟨hal-03430371⟩