What was done
The main objective of the authors was "to review documented evidence of the impacts of climate change trends on forest productivity since the middle of the 20th century."

What was learned
In an analysis that cited 186 scientific journal articles, Boisvenue and Running determined that "globally, based on both satellite and ground-based data, climatic changes seemed to have a generally positive impact on forest productivity when water was not limiting," which was most of the time, because they report that "less than 7% of forests are in strongly water-limited systems." More specifically, of the 49 scientific papers they reviewed that contained relevant data, they say that "37 showed a positive growth trend, five a negative trend, three reported both a positive and a negative trend for different time periods, one reported a positive and no trend for different geographic areas, and two reported no trend."

What it means
In spite of what climate alarmists routinely describe as unprecedented increases in the "twin evils" of the radical environmentalist movement, i.e., atmospheric CO2 concentration and air temperature (a situation that some of them have described as being a greater threat to the world than either global terrorism or nuclear warfare), there has in fact been what Boisvenue and Running call a significant "greening of the biosphere."

How out of tune with reality can some people get?