I haven't had a lot of time lately, but I ran the math on my plan to solve global warming by planting trees, using Wolfram Alpha, which has access to significantly more figures than I do. I'm not encouraged.
Taking the most extreme position possible, suppose we covered the entire land surface of the earth with Pawlonia Tormentosa, a fast growing, carbon sucking tree. These trees are planted every 25 feet across every part of the earth not covered in water. Homes, businesses, farms, freeways, and anything else we want to do on the earth is buried beneath. This works out to 1.12 trillion trees.
Each tree sucks, over the course of about 7 years, about 3*106 grams of carbon straight out of the air. At this point, it can be cut down and it will regrow from its own stump. The wood would then have to be not burned, but instead either buried or made into objects that we plan to keep for a while, such as houses. Based on the weight of the wood, the number of trees, Wolfram Alpha found that every seven year cycle would suck, assuming I didn't make a decimal point error here, 74 parts per million of carbon dioxide out of the air. In this time, human activity would replace another 35 ppm, what with all the coal and oil we've been burning. To reduce the carbon levels from the current high of 393ppm to the pre-industrial level of 180 ppm would take 7 cycles of this -- 49 years.
This isn't going to happen. Much of the earth could not sustain a forest so thick that the branches of neighboring trees touch. There's deserts, where the trees would die from lack of water, mountains where the trees sap would freeze so hard that the tree would literally explode, beaches where the salted earth would drain the moisture back to the soil, killing the tree. We could not move our farms underground without an explosive increase of our energy use to keep our farms lit and alive, not to mention watered. And if we're not willing to install solar panels and drive hybrids for the sake of the earth, we certainly aren't willing to live like murlocks in little caves. We like the sun and the breeze and the other amenities of the surface world.
The best solution is clearly a compromise between these insane extremes. More solar, less coal, trees where it makes sense, wooden structures where it doesn't. Slow the change to the point where we can adapt to it as it comes.