The remainin budget for a reliable chance (83%) of not exceeding 1.5˚C global warming has been expended –
After making all these changes, our best (50%) RCB estimate starting from 2022 is 250 GtCO2 (17–83% range from uncertainty in the impact of CO2: −170 to 840 GtCO2) for the RCB for limiting warming to 1.5 °C. The same uncertainty in the modelled impact of non-CO2 forcing gives a range of 160–280 GtCO2. We can combine these uncertainties using a generalized extreme values functional fit to the quantiles (described in Methods), resulting in a range of –200 to 830 GtCO2.
Assessing the size and uncertainty of remaining carbon budgets