Stop Disasters
Open the Future has an excellent post on "Stop Disasters", a game whose goal is "to reduce the harmful results of catastrophic natural events -- the disaster that gets stopped isn't the event itself, but its impact on human life".
Like a miniature version of SimCity, the Stop Disasters game features a tile-based game where it is up to you to build disaster defenses, create housing and hospitals, and disaster mitigation infrastructure, all within a limited financial budget and time.
I played one disaster scenario (tsunami), and enjoyed it, although I unfortunately failed to save 62 lives. I look forward to improving my game and playing the other scenarios.
It would be wonderful to see some games around global climate change, environmental sustainability, peak oil, and water shortages.