Soil moisture-atmosphere feedback controls more than half of total climate effects on land carbon uptake

The global land carbon sink is reduced by climate change, in particular by extreme events such as droughts, heatwaves, and fires^1,2. Soil moisture, including its feedback on atmospheric conditions (SA), was identified as one of key drivers of these climate extremes^3-6 and contributes to the negative climate effects on the land carbon uptake^7,8. However, the extent to which the total climate impact on land carbon uptake can be explained by SA feedback remains unknown. Here, we develop an analytical framework utilizing multiple factorial model experiments to show that SA feedback contributes more than half (–61.6 ± 10.4%) of the total climate effect on land carbon uptake at a global scale during 1981–2014, with the largest contributions from hot and dry regions. The strengthened SA feedback has shifted the climate impact on land carbon uptake from near-neutral during 1981–1997 to largely negative during 1998–2014, primarily by weakening photosynthesis. By the end of the twenty-first century, projected reductions in land carbon uptake caused by the SA feedback could even double under a high emission scenario relative to the historical period, driven by increased soil moisture variability. Our findings highlight that SA feedback will potentially dominate the response of long-term land carbon uptake to climate change.