There's a good reason that the effect causing global warming is called the Greenhouse Effect, and CO2 a greenhouse gas. It comes from the use in greenhouses. The effect has been known for well over a century (which makes it all the more odd there's so much political resistance now to accept that this is happening).

And while more plants is certainly a nice thing, there's more to having a healthy planet than just having more plants, especially when it comes at the cost of melting ice caps and changing weather patterns, possibly leading to desertification and less plants in other places.

Although according to the article, this particular increase in greenery is mostly due to projects to plant more trees in Indian and China, and investments into agriculture. All of them good things that don't really need more CO2 in the atmosphere.