摘要：The remaining carbon budget quantifies the future CO2 emissions to limit global warming below a desired level. Carbon budgets are subject to uncertainty in the Transient Climate Response to Cumulative CO2 Emissions (TCRE), as well as to non-CO2 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 GtCO2 emitted. Considering only geophysical uncertainties, our median estimate of the 1.5 C remaining carbon budget is 440 GtCO2 from 2020 onwards, with a range of 230-670 GtCO2, (for a 67-33% chance of not exceeding the target). Additional socioeconomic uncertainty related to human decisions regarding future non-CO2 emissions scenarios can further shift the median 1.5 C remaining carbon budget by 170 GtCO2. Integrating uncertainties using insights from both observations and models narrows the range on the remaining carbon budget for 1.5 C, as well as the transient climate response to cumulative CO2 emissions.
