I was privileged to participate in a tree planting project -- 10 trees on 10/10/10 -- organized by Transition Town Charlotte in conjunction with 350.org. 350.org, organized by Bill McKibben and Middlebury College students, enlisted hundreds of thousands of people in 188 countries and throughout the U.S. to take part in more than 7300 events to call attention to the fact that the max sustainable CO2 concentration in the Earth's atmosphere is 350 ppm. Currently it is around 390 ppm, which is contributing to global warming and climate change. See more at http://www.350.org/en/about/science and http://www.350.org/en/node/17812.
