The coefficient of variation (COV) for each grid is calculated as 100×standarddeviationmean to evaluate seasonal and interannual SST stability, which increases with decreasing COV for each grid. The monthly and interannual effects of various atmospheric parameters, i.e. NAOI, SLP, P, TCC, τax, τay and T2m, and of air-sea heat fluxes on SST variability are studied using the correlation coefficient (R) and number of observations

(n). All correlation coefficients have been tested for significance at the 95% level; however, the t-test is used to examine the significance (at 95%) of all the linear trends. τax and τay are calculated using a standard bulk formula: τax=ρaCDUW,τay=ρaCDVW, where ρa (1.3 kg m− 3) is the air density, CD is the

air drag coefficient, U and V are the wind components in the x and y directions, respectively, and NU7441 W is the wind speed. The selleck air drag coefficient is calculated in its non-linear form ( Large & Pond 1981), modified for low wind speeds as in Trenberth et al. (1990): CD=0.00218forW≤1ms−1,CD=0.62+1.56/W0.001for1ms−1

together with historical CMIP5 results for the 1982–1999 period were tested using AVHRR SST data. Direct monthly and annual biases (i.e. CMIP5 ensemble mean minus AVHRR) were used to evaluate the accuracy of the CMIP5 over the 1982–2012 period. The CMIP5 ensemble mean was calculated based on 24 global climate models computed at KNMI (http://climexp.knmi.nl/select.cgi). The 30-year running average SST over the 21st century was calculated to illustrate future trends and uncertainties based on the four CMIP5 scenarios used. This evaluates the most important factor affecting the projected SST at the end of this century, including its seasonal, regional and emissions variations. The Mediterranean SST and the seasonal and annual climatology-averaged SST of the Mediterranean’s adjacent regions will be used to describe the SST dynamics. The annual average Mediterranean SST is calculated to be 19.7 ± 1.3 °C (Figure 2a). The much warmer water, calculated on the basis of two standard deviations from the mean (> 22.4 °C), occurred over only 0.