Recent intensification of the negative physiological effect of CO2 on terrestrial evaporation

Atmospheric carbon dioxide (aCO 2 ) directly modulates global terrestrial evaporation (ET) through two counteracting plant physiological effects: vegetation greening and a reduction in stomatal conductance. The extent to which these two aCO 2 physiological effects translate into ET trends, and their individual contributions, are still subjects of debate. Here we present a novel analog framework to decouple and quantify their respective contributions using a suitable global dynamic vegetation model ensemble from the TRENDY project, rigorously constrained by satellite observations. Our analysis, enabled by isolating the aCO 2 physiological effect, reveals that the net physiological effect of CO 2 on ET is globally negative during 1982–2018, as stomatal conductance reductions overcome the positive effect of greening. However, in water-limited arid regions, the decoupled effect shows a near-zero positive response. As aCO 2 has increased in recent decades, this net negative physiological effect on ET has progressively intensified and is expected to attenuate the projected increases in ET due to global warming and the consequent acceleration of the water cycle.