Terrestrial ecosystems have absorbed approximately 32 % of total anthropogenic CO emissions over the past six decades ₂ ¹ . However, large uncertainties in terrestrial carbon–climate feedbacks make it difficult to predict how terrestrial carbon sequestration will respond to future climate change ² . Interannual changes in the growth rate of atmospheric CO ₂ (CGR) are dominated by land-atmosphere carbon fluxes in the tropics, providing an opportunity to investigate carbon-climate interactions on land ^{3 , 4 , 5 , 6} . CGR changes are believed to be largely controlled by temperature ^{7 , 8 , 9, 10} , but there is also evidence of a close relationship between water availability and CGR ¹¹ . Here we use records of global atmospheric CO ₂ , terrestrial water storage, and precipitation data to investigate changes in the interannual relationship between tropical landscape climatic conditions and CGR in a changing climate. We find that the interannual relationship between tropical water availability and CGR has become increasingly negative in 1989–2018 compared to 1960–1989. This could be related to spatiotemporal changes in tropical water availability anomalies caused by shifts in the El Niño/Southern Oscillation teleconnection, including decreasing spatial compensatory effects of water ⁹. 

(Laibao Liu, Philippe Ciais, Sonia I. Seneviratne)