Bill McKibben, author of The End of Nature, founded the group 350.org to generate public action around the world to demand that world leaders work towards a goal of 350 parts per million CO2 in the atmosphere. The group has called for worldwide demonstrations on October 24.

For a list of events in your area, go to www.350.org.

Our air is currently at about 390 parts per million CO2 and the level is increasing by about 2 ppm each year, primarily as a result of burning of fossil fuels such as coal, oil, and gas. The pre-industrial revolution level was 278 ppm. Leading NASA climate scientist James Hansen has warned that to avoid climate-related catastrophes we need to roll back CO2 concentrations to 350 parts per million, starting right now. Target Atmospheric CO2: Where Should Humanity Aim? http://pubs.giss.nasa.gov/docs/2008/2008_Hansen_etal.pdf 
Earlier reports from the Nobel prize winning Intergovernmental Panel on Climate Change (IPCC) had indicated that the dangerous levels of CO2 would be more in the range of 450 parts per million, but that was before scientists recognized the rapid impacts of feedback processes, such as melting ice and the release of greenhouse gases by the soil and oceans in a warming climate, and observed the actual current rates of change, especially at the poles. The head scientist at the IPCC head, Rajendra Pachauri, now supports a carbon dioxide limit of 350 parts per million. 

At the December climate change treaty meeting in Copenhagen governments will try to reach agreement on the next stage of international climate responses. Many poorer countries are unwilling to make substantial commitments to CO2 reductions without action by the United States, which is responsible for about 25% of greenhouse gas emissions, and did not sign on to the previous Kyoto Protocol emissions reduction targets. 350.org actions in the US are intended to show support for substantial US commitments on CO2 emission reductions.

Watch http://www.youtube.com/user/350org