Fig. 2: Representations of internal variability in observed and modeled gradient trends.
a Heatmaps presenting mean values of observed linear trends in the tropical Pacific zonal sea surface temperature gradient (ΔSSTwest-east) with the trend start years on the x-axis and the trend end years on the y-axis (the primary diagonal represents trends of 20 years, and the upper left corner represents the longest trend of 153 years). Hatching indicates trends captured by the range of internal variability in each large ensemble, and inset percentages indicate the proportion of all trends that are not captured. Models are in descending order of the percentage of the observed trends that they capture. b Standard deviation of trends in observations and large ensembles for trend lengths up to 140 years. c Standard deviation distributions of detrended zonal gradient over the period 1870–2024 for models (in boxplots, orange line represents median, box represents interquartile range, whiskers represent 90% range and circles represent outliers) and five observational products (blue shaded region; note that some products do not span full time range); models with standard deviation in observational range (gray shaded region). a–c Red triangles or red lines indicate models in Group A (for which more trends are captured when the forced response is removed), blue triangles or blue lines indicate models in Group B (for which a similar number or fewer trends are captured when the forced response is moved).
