The study investigates the global greening trend of vegetation from 1982 to 2009 using three long-term satellite leaf area index (LAI) records and ten global ecosystem models. The analysis reveals a persistent and widespread increase in growing season integrated LAI (greening) over 25% to 50% of the global vegetated area, while less than 4% of the globe shows decreasing LAI (browning). The factorial simulations with multiple global ecosystem models suggest that CO2 fertilization effects explain 70% of the observed greening trend, followed by nitrogen deposition (9%), climate change (8%) and land cover change (4%). CO2 fertilization effects are most prominent in the tropics, while climate change contributes to greening in high latitudes and the Tibetan Plateau. Land cover change is significant in southeast China and the eastern United States. The regional effects of unexplained factors suggest the need for further exploration in the next generation of ecosystem models, including forest demography, regional management intensities, and other productivity constraints. The study highlights the significant alteration of terrestrial vegetation's productive capacity due to anthropogenic influences.The study investigates the global greening trend of vegetation from 1982 to 2009 using three long-term satellite leaf area index (LAI) records and ten global ecosystem models. The analysis reveals a persistent and widespread increase in growing season integrated LAI (greening) over 25% to 50% of the global vegetated area, while less than 4% of the globe shows decreasing LAI (browning). The factorial simulations with multiple global ecosystem models suggest that CO2 fertilization effects explain 70% of the observed greening trend, followed by nitrogen deposition (9%), climate change (8%) and land cover change (4%). CO2 fertilization effects are most prominent in the tropics, while climate change contributes to greening in high latitudes and the Tibetan Plateau. Land cover change is significant in southeast China and the eastern United States. The regional effects of unexplained factors suggest the need for further exploration in the next generation of ecosystem models, including forest demography, regional management intensities, and other productivity constraints. The study highlights the significant alteration of terrestrial vegetation's productive capacity due to anthropogenic influences.