Figure 2: Global mean surface temperature trends and p values. a,b, 20-year (a) and 15-year (b) running trends. Black curves are ensemble-averaged trends over the 37 sets of model simulations. Dark-grey shading indicates the 2.5–97.5% ranges of the simulated estimates. Light-grey shading shows the 95% uncertainty ranges of the ensemble means, derived by dividing the 2.5–97.5% ranges by the square root of the number of models. Red curves are the observed trends averaged over 100 realizations and the horizontal red lines show the observed 1900–2012 trends averaged over 100 realizations. Black cross-hatchings are the 95% uncertainty ranges for simulated 1900–2012 ensemble mean trends. Note that the observed and simulated long-term trends are very similar to one another, and are smaller than the short-term trends. c,d, 20-year (c) and 15-year (d) p values on trend differences between the simulations and observations for assumption (1) (purple curves), or assumption (2) (green curves). The horizontal dashed lines indicate the threshold below which we reject the null hypothesis.
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