Are "greening" and "browning" terms with specific scientific meaning? I'm concerned that the comments you've copied and pasted are out of context, irrelevant to the discussion at hand (global warming will cause significant deleterious public health effects, and soon - food shortage or surplus notwithstanding), and also not peer-reviewed (I can't find the source article for Zaichan Zhu et. al - please provide if possible). While higher CO2, and higher temperatures, may be good for some plants/crops, the reality is that global warming is NOT good for humankind in general. For a multitude of reasons, many of which were detailed in the original commentary above.