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

ranging from 29˚C in the northern part to 33˚C in the southern part. Under scenario RCP4.5 the spatial pattern is very similar, but the warming is lower, with values ranging from 26˚C in the north to 31˚C in the south. Additionally, we assess the uncertainty by looking at the ensem- ble spread. Due to the limited size of the ensemble (8 models), we evaluated the minimum and maximum values and the std from the ensemble (Fig 7, Table 3). Under scenario RCP8.5 the minimum projected values are 27˚C in the northern part while the maximum ones can be found in the southern part (34˚C). Under scenario RCP4.5, the minimum values would be 25˚C in the northern part and the maximum projected values are 31.5˚C in the southern part. In order to analyse the rate of change throughout the century, linear trends have been fitted to the average surface temperature for two periods (Fig 9): 2006–2050 (period 1) and 2051– 2100 (period 2). For the RCP 4.5 scenario, the trends are 0.23˚C/decade and 0.11˚C/decade, respectively. For RCP 8.5, the trends are 0.31˚C/decade and 0.47˚C/decade, respectively. Therefore, under scenario RCP4.5 there is a deceleration of the warming in the upper layers after 2050, while under scenario RCP8.5 is the opposite, with warming increasing after 2050. Fig 7. SST increase at the end of the century (2080–2100) with respect to the present climate (1985–2005) under the RCP8.5 scenario for the selected GCMs (RCP 8.5). https://doi.org/10.1371/journal.pone.0255505.g007

Table 3. Ensemble results for the basin averaged SST anomalies in the Red Sea (in ˚C) at the end of the century (2080–2100). The ensemble mean and spread (STD) along with the ensemble minimum and maximum values are presented for scenario RCP4.5 and RCP8.5. RCP4.5 (2080–2100) RCP8.5(2080–2100) Ens. Mean Ens. STD Ens. Min Ens. Max Ens. Mean Ens. STD Ens. Min Ens. Max Del_SST (˚C) 1.57 0.37 0.83 1.96 3.32 0.65 2.17 4.20 Del_T(0-225m) (˚C) 1.38 0.33 0.95 1.71 2.84 0.54 1.91 3.62 https://doi.org/10.1371/journal.pone.0255505.t003 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 13 / 26