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

(most likely 2045). In those periods and scenarios the SST increase in the Red Sea would be of only 0.7 ± 0.6˚C, which also matches the results obtained with 3 GCMs under scenario RCP2.6 by [13]. Therefore, it is clear that the expected impacts in the Red Sea in terms of mean warm- ing but also in terms of MHWs would be much reduced under a scenario of strong mitigation. Conclusions In this work we have assessed the skills of coarse resolution GCMs in reproducing the heat content variablity of the Red Sea. Namely we used different diagnostics on the seasonal, inter- annual and long-term variability of the temperature field. The results have shown very diverse results for the different GCMs, with almost half of them being unacceptable under the pro- posed criteria. However, we have also found a limited subensemble of 8 GCM models that show acceptable skills in most of the diagnostics, at a level comparable to two reference high resolution simulations. The selected subensemble was then used to project the temperature evolution in the Red Sea and the Gulf of Aden under a business-as-usual scenario (RCP8.5) and a moderate scenario (RCP4.5). The models project a larger warming under the former (3.3 ±0.6˚C at the surface for the period 2080–2100) than under the latter (1.6 ±0.4˚C at the surface for the period 2080–2100). Also, the models consistently showed that under scenario RCP8.5 the water column would become more stratified, while under scenario RCP4.5 the warming is expected to be quite homogenous in depth. This rise of the mean temperature

would also affect the characteristics of marine heat waves. At present, the number of days with Fig 12. Daily SST averaged in the north (Top panel), south (middle panel) and Outer Region (bottom panel) for present conditions (grey), under scenario RCP 4.5 (light blue) and under scenario RCP8.5 (orange). The dots indicate the occurrence of MHWs in present conditions (black), under scenario RCP 4.5 (blue) and under scenario RCP 8.5 (red). For clarity only a limited period is plotted (1998–2003 for the present conditions, bottom axis and 2090–2096 for the future conditions, top axis). https://doi.org/10.1371/journal.pone.0255505.g012 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 21 / 26