Very interesting article from some folks at Google that worked intensively on improving the renewable energy landscape. It puts a damper on some of my hopes that cheap, widespread solar and improvements in battery technology will help replace our use of fossil fuels. It offers some interesting ways forward also.
One thing I think people don't realize is that population growth is slowing substantially and humans are increasingly living in cities. This is freeing up land that can go 'back to nature' and -- as pointed out in this article -- serve as a planting ground (in some regions) for reforestation, nature's carbon sequestration.