In 2008, environmentalist and writer Bill McKibben and a small group of students from Middlebury College set out with one goal: to reduce the parts per million (ppm) of carbon in the atmosphere. The group derived its name from a paper by NASA climate scientist James Hansen that found 350 ppm of carbon to be the upper limit, or tipping point, in the atmosphere. Just one year previously in 2007, McKibben led his "Step It Up" campaign that involved demonstrations in 1,400 cities across the US. After this, McKibben and the students set out to shift that mission from national to global.
The group gained a significant amount of traction in 2009 after McKibben appeared on the Colbert Report. In 2012, the group received the Katerva Award for behavioural change.
350.org consists of hundreds of staff members and thousands of volunteers from around the world, as detailed by their team page. They prepend words like "Chief" and "Lead" to certain titles suggesting some sort of hierarchical structure to decision making. The top-most level is an extremely diverse 9-person board which reflects the diversity of their entire team. Most of their impact, though, comes from the thousands of volunteers that demonstrate on a global scale.