Assessment of Red Sea temperatures in CMIP5 models for present and future climate

patterns in the Indian Ocean. Thus, in our case, the isolation of the Red Sea from open ocean dynamics makes easier for the GCM to represent the heat content variability. The temperature projections have been done based on the ensemble of 8 models that have met acceptable levels in selected diagnostics. Those diagnostics have been selected to reach a balance between the number of requirements and the number of models that are needed for the computations. However, as we have mentioned above, there is an unavoidable degree of subjectivity in any model selection procedure. Therefore, for completeness we have computed also the projected SST anomaly for different subensembles created following different criteria (Table 1). The results show that depending on the criterion chosen the projected SST increase under scenario RCP8.5 would range between 3.15˚C and 3.45˚C (S10 Fig). The former is obtained using criterion 1, the most restrictive, in which only 2 models complied (see Table 2). The latter was obtained using criterion 4, but in this case, there were no requirements on the GCM trends (Table 2). Namely, models with present climate trends larger than the observed range (including uncertainties) are kept and drive the ensemble towards larger projected anomalies. Therefore, the selected criterion (number 2), seems to provide a good compromise, between realistic representation of key processes and the number of models kept in the ensem- ble. Nevertheless, the final results would not have changed significantly if other criterion

would have been selected (difference lower than 10%; see S10 Fig). A note of caution is needed here. Although we think the selected GCMs provide a reason- ably quality in reproducing Red Sea temperature variablity, the projections reported here have Fig 11. Air temperature at 1000 mbars (x-axis) and 0-100m sea temperature (y-axis) in the Red Sea. A high-pass filter has been applied to remove multidecadal variations. https://doi.org/10.1371/journal.pone.0255505.g011 PLOS ONE Assessment of Red Sea temperatures in CMIP5 models for present and future climate PLOS ONE | https://doi.org/10.1371/journal.pone.0255505 July 30, 2021 19 / 26