If you accept that the climate is warming, regardless of the reasons for the change, you'd pretty much have to accept also that there will be changes in the distribution and growth patterns of vegetation. Predicting the effect on individual plant species would be difficult at best, but suggesting that some degree of warming will affect all plant species in a given area the same way, that is will favor increased growth for all, for instance, is certainly contrary to the obvious fact that some plants do better in warm climates and some favor cooler climates. In my area we seem to be shading from zone 5 to zone 6, which will be good for my pecans, I hope. On the other hand, we might also start seeing more kudzu. If the kudzu comes I hope it eats the darn wild grape!
Chuck