An integrated approach to quantifying uncertainties in the remaining carbon budget
H. Damon Matthews, Katarzyna Tokarska, Joeri Rogelj, Chris Smith, Andrew H. MacDougall, Karsten Haustein, Nadine Mengis, Sebastian Sippel, Piers Forster, Reto Knutti
Abstract
Abstract The remaining carbon budget quantifies the future CO 2 emissions to limit global warming below a desired level. Carbon budgets are subject to uncertainty in the Transient Climate Response to Cumulative CO 2 Emissions (TCRE), as well as to non-CO 2 climate influences. Here we estimate the TCRE using observational constraints, and integrate the geophysical and socioeconomic uncertainties affecting the distribution of the remaining carbon budget. We estimate a median TCRE of 0.44 °C and 5–95% range of 0.32–0.62 °C per 1000 GtCO 2 emitted. Considering only geophysical uncertainties, our median estimate of the 1.5 °C remaining carbon budget is 440 GtCO 2 from 2020 onwards, with a range of 230–670 GtCO 2 , (for a 67–33% chance of not exceeding the target). Additional socioeconomic uncertainty related to human decisions regarding future non-CO 2 emissions scenarios can further shift the median 1.5 °C remaining carbon budget by ±170 GtCO 2 .