Likelihood of climate change pathways under uncertainty on fossil fuel resource availability

Uncertainties concerning fossil fuel resource availability have traditionally been deemphasized in climate change research as global baseline emission scenarios (i.e., scenarios that do not consider additional climate policies) have been built on the assumption of abundant fossil fuel resources for the 21st century. However, current estimates are subject to critical uncertainties and an emerging body of literature is providing revised estimates. Here we consider the entire range of revised estimates, applying an integrated assessment model to perform a likelihood analysis of climate change pathways. Our results show that, by the end of the century, the two highest emission pathways from the IPCC, the Representative Concentration Pathways RCP6 and RCP8.5, where the baseline scenarios currently lie, have probabilities of being surpassed of 42% and 12%, respectively. In terms of temperature change, the probability of exceeding the 2 °C level by 2100 remains very high (88%), confirming the need for urgent climate action. Coal resource uncertainty determines the uncertainty about the emission and radiative forcing pathways due to the poor quality of data. We also find that the depletion of fossil fuels is likely to occur during the second half of the century accelerating the transition to renewable energy sources in baseline scenarios. Accordingly, more investments may be required to enable the energy transition, while the additional mitigation measures would in turn necessitate a lower effort than currently estimated. Hence, the integrated analysis of resource availability and climate change is essential to obtain internally consistent climate pathways.