We should be doing this in the U.S., especially California. When I was an undergrad at Berkeley, I took geography from Professor Barney Nietschmann. I had a crush on him, but I digress. Anyway, he mentioned that more greenery and forests attract more clouds and create more rain. The California Academy of Sciences in San Francisco has this type of roof, and I also saw a roof like this in Vancouver in preparation for the Olympic games. There is so much new money in San Francisco, and new buildings going up, that efforts should be made to do this. One of the commenters at the bottom of the post raises good arguments against solar panels and having plants on the roof. I wonder how proponents of this technology would address his concerns?