Climate tipping points within the. XXI century COACCH D3.2 (Scoccimarro et al., 2020) identifies and analyzes four different climate tipping points and the associated probability of occurrence within the XXI century: global extreme sea- level rise, Alpine glaciers disappearance, disappearance of Arctic Summer Ice and the slowdown of thermoaline circulation. Main conclusions from the analysis are the following: Regarding Global Sea Level Rise, (CT1) the tiping point can originate from the melting of the polar ice sheets. Despite the uncertainty in ice-sheet response, it can be stated that in RCP2.6 and RCP4.5 high end SLR of more than 1.0 m is extremely unlikely within the current century, same as for RCP8.5 until 2050. However, it is about as likely as not that high end – more than 1.0 m will occur until 2100. Regarding Alpine glaciers disappearing,(CT2) considering 10% of the current cover as a threshold to define the Alpine glacier disappearing, only few ensemble members suggest that this could be reached within 2100. Nonetheless, average reductions in the order of 80% / 60% are expected for the end of the century already in the RCP4.5 / RCP2.6 scenario. Regarding Arctic Summer sea-ice disappearance, (CT3), associated abrupt changes in atmospheric circulation are not exected within the century. Relevant ice melting, however can be expect within the current century, at least under RCP8.5. Therefore, more regions in the Arctic will become less dangerous for navigation. Regarding the slowdown of the thermohaline circulation in the Atlantic basin (CT4), it results that the chance of abrupt transition or collapse in the 21st century for the scenarios considered is very unlikely. In the light of these outcomes the following analysis focuses just on the first three climate tipping points. Qualitative discussion of CT4 is reported in Scoccimarro et al. (2020)
