In this paper we pose the following question: assume one wants to limit warming to a specific threshold in the year 2100, while accepting a certain risk tolerance of exceeding it, then when, at the latest, does one have to start to ambitiously reduce fossil fuel emissions? The point in time when it is “too late” to act in order to stay below the prescribed threshold is called the point of no return (PNR; van Zalinge et al., 2017). The value of the PNR will depend on a number of quantities, such as the climate sensitivity and the means available to reduce emissions. To determine estimates of the PNR, a model is required of global climate development that (a) is accurate enough to give a realistic picture of the behavior of GMST under a wide range of climate change scenarios, (b) is forced by fossil fuel emissions, (c) is simple enough to be evaluated for a very large number of different emission and mitigation scenarios and (d) provides information about risk, i.e., it cannot be purely deterministic.
Click here to learn more.