Fig. 1: Tropical land climate–carbon interannual relationships.
From: Increasingly negative tropical water–interannual CO2 growth rate coupling
a, Yearly tropical temperature versus tropical WS versus CGR in detrended anomalies. The values of CGR are indicated by the colour bar. b, Histograms of climate–CGR interannual correlations in the first three decades (1960–1989) and in the more recent three decades (1989–2018), derived using 5,000 bootstrapping repeats. Both tropical WS and LagP are used to represent tropical water availability. c, As for b but showing histograms of the partial correlations of CGR to tropical temperature and tropical water after controlling tropical water and tropical temperature, respectively. d, Histograms of the interannual sensitivity of CGR to tropical WS (γWS) and LagP (γLagP) in the univariate regression for the same two periods, derived using 5,000 bootstrapping repeats. Unlike correlations, γWS and γLagP differ in magnitude because of the differences in WS and LagP IAV magnitude and are therefore shown separately. The unit of this sensitivity is PgC yr−1 per Tt H2O. e, As for d but showing γWS and γLagP estimated using the bivariate regression with both tropical water and tropical temperature as predictors. Ridge regression is used here to reduce biases from high collinearity between water and temperature (Methods).
