US greenhouse gases drop to 15-year low

This is a good example about how changes in the behavior of citizens has a major impact in greenhouse gases. This did not happen because of regulations or restrictions, but rather by citizens voluntary reduced usage related to a tough economy.

source: http://www.ft.com/cms/s/0/dfc8a384-6a06-11e0-86e4-00144feab49a.html#axzz1JysgrijO

source1: http://www.solarnavigator.net/greenhouse_gases.htm