I hear you, Bostonian; my 5 year-old is totally worried about global warming, too.
You mentioned you were seeking books and you appear to be trying to help your kid better understand the (complicated) science. That's awesome. My son's younger and we're exploring global warming from a different angle. Not sure what is of interest to you or your son but here's what's been great for us:
1. Seeing things happening that are really positive, e.g. a house with alternative energy systems, an off-grid organic farm. We're going to visit a solar farm and a green industrial facility soon. My son worries about these big issues and seeing good things happening is uplifting (for me, too)!
2. Doing cool and useful things to address global warming ourselves: planting a veggie garden, biking or walking instead of driving--and having fun doing it!
3. Helping our kid understand that his is not alone in his concerns. We've enjoyed the photos from around the world at 350.org (they had a global work day where people around the world did projects and took photos of themselves to rally for limits to CO2 in the atmosphere--and there are pictures from remote areas in Africa, from the Marshall islands--from EVERYWHERE. It's stunning--some cool and fun and creative ideas are shown in these photos! If you want to check them out, they are at:
http://www.350.org/sites/all/files/bigpicture.html The next global work day is Sept. 24th.
My son's concerns have encouraged us to be more responsible. Which, surprisingly, has been really FUN for our family--less time in the car, more time on the bike, time in the garden, learning about cool things happening nearby--not a bummer at all!
Anyhow, good luck finding awesome ways to explore with your son! I'd love to hear what other families are doing to address their kid's concerns about global warming. Good luck to all!
