Because of increasing CO2 levels, the world becomes greener. Here is a particular result about this:
Global environmental change is rapidly altering the dynamics of terrestrial vegetation, with consequences for the functioning of the Earth system and provision of ecosystem services. Yet how global vegetation is responding to the changing environment is not well established. Here we use three long-term satellite leaf area index (LAI) records and ten global ecosystem models to investigate four key drivers of LAI trends during 1982–2009. We show a persistent and widespread increase of growing season integrated LAI (greening) over 25% to 50% of the global vegetated area, whereas less than 4% of the globe shows decreasing LAI (browning). 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 (LCC) (4%). CO2 fertilization effects explain most of the greening trends in the tropics, whereas climate change resulted in greening of the high latitudes and the Tibetan Plateau. LCC contributed most to the regional greening observed in southeast China and the eastern United States. The regional effects of unexplained factors suggest that the next generation of ecosystem models will need to explore the impacts of forest demography, differences in regional management intensities for cropland and pastures, and other emerging productivity constraints such as phosphorus availability.
Here a map for the change from 1982-2015:
and here another one for the change from 2000-2017:
The fact that the Earth became greener during the last decades is simply a fact of observation. The explanations, namely that 70% have been caused by more CO2 fertilization, and another 8% by warming, are, of course, based on the use of various climate models. Nonetheless, they sound quite plausible too. Recent research has also found human activity as an important contribution, in particular in China and India:
So, China’s outsized contribution to the global greening trend comes in large part (42%) from programs to conserve and expand forests.
First of all, CO2 is really a positive contribution to plant growth, and this effect is quite important.
Then, climate change - warming as well as more precipitation - also positively contributes to more plant growth.
Last but not least, human contributions can change a lot in positive direction too.