Fig. 4: 95% confidence interval in annual GPP trends for 1991–2020. | npj Climate and Atmospheric Science

Fig. 4: 95% confidence interval in annual GPP trends for 1991–2020.

From: When is a trend meaningful? Insights to carbon cycle variability from an initial-condition large ensemble

Fig. 4

a The 95% confidence interval was obtained from the 50-member ensemble. It is the range of trends (n = 48) after excluding the smallest and largest trends for each grid cell. b The 95% confidence interval obtained from the standard error of the regression trend (\({s}_{b1}\), Eq. 3). The confidence interval is \(2* 2.048* {s}_{b1}\), where \({t}_{\mathrm{0.975,28}}=2.048\) is the critical t-value for \(n=30\) years of data. Shown is an ensemble member chosen at random. Stippling shows where the trend is statistically significant (n = 30 years; p ≤ 0.05). c Frequency distribution of the 95% confidence interval obtained from \({s}_{b1}\) for the n = 50 ensemble members at the grid cell corresponding to the D01: Northeast location. The confidence interval for each ensemble member is calculated as in (b). The thick black line is the 95% confidence interval obtained from the 50-member ensemble as in (a). d As in (c), but for D19: Taiga.

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