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Abstract

Atmospheric vapor pressure deficit (VPD) is a critical variable in determining plant photosynthesis. Synthesis of four
global climate datasets reveals a sharp increase of VPD after the late 1990s. In response, the vegetation greening
trend indicated by a satellite-derived vegetation index (GIMMS3g), which was evident before the late 1990s, was
subsequently stalled or reversed. Terrestrial gross primary production derived from two satellite-based models
(revised EC-LUE and MODIS) exhibits persistent and widespread decreases after the late 1990s due to increased
VPD, which offset the positive CO2 fertilization effect. Six Earth system models have consistently projected con-
tinuous increases of VPD throughout the current century. Our results highlight that the impacts of VPD on veg-
etation growth should be adequately considered to assess ecosystem responses to future climate conditions.