I have been reading the Skeptical Environmentalist, and one graph just blew me away. On page 300, he cites research that estimates the total amount of life on earth will greatly increase over the next 100 years due to increased carbon dioxide levels in the air and elevated temperatures.
Net Primary Productivity is estimated to increase 40% over the next 100 years from 60 billion tons to 85 billion tons. NPP is a measure of the amount of sunlight that plants and plankton capture and turn into biomass. See this previous post for a video of NPP in action.
As NPP increases, there is more food at the bottom of the food chain, which allows for more life higher up. Total biomass will increase 35% from 700 billion tons to 950 billion tons. I haven't been able to confirm this number elsewhere (but I did email NASA, so we will see if they respond), but if true, it is a very positive thing for people who like life on earth and want more of it.