Fig. 2: Change in tropical mean SST–rainfall relationship.
a Scatter plot of CMIP6 multi-model mean monthly SST and rainfall at all grid points in the tropics [20°S–20°N], obtained from the time averages of historical simulation of 1950–1999 (T<20th> and P<20th>; blue) and SSP5-8.5 simulation of 2050–2099 (T<21st> and P<21st>; red), and the pseudo future reconstruction of 2050–2099 based on T<20th> + ΔT and P<20th> (sky-blue; ΔT = T0<21st> − T0<20th>). The colored shading indicates the slope of saturated vapor pressure change to SST change (dEs/dT). The star symbols show the mean position of Niño3 region. PT, rainfall as a function of SST, was calculated by a piecewise function (3rd-order polynomial fit, in T < Tc; Gaussian function fit in T > Tc; see “Methods” for details). The black, dark green, and light green lines show the fitted PT for present, pseudo future, and future climate, respectively. Simulated frequency histograms for b SST (f(T)) and c rainfall (g(P)) and d fitted rainfall histogram as a function of T (g(PT)) over the tropics (shading) and Niño3 region only [5°S–5°N, 150°W–90°W] (solid line) are shown as inserts. The fitted rainfall histogram of pseudo future reconstruction over the tropics (sky-blue dashed line in d) is also displayed.
