350 parts per million. That’s the level of atmospheric carbon dioxide beyond which many scientists warn the
earth’s climate may begin to spiral out of control. At higher
concentrations, they say, heat-reflecting ice sheets will disappear and
permafrost will melt, releasing vast amounts of additional greenhouse
gases and driving sea levels higher in a vicious cycle. The earth’s
atmosphere is currently at around 380 parts per million, and climbing.
For a young international movement, 350 is a rallying cry, an organizing principle. On October 24th, climate activists in over 180 countries with the group 350.org
staged more than 5,200 demonstrations, pressuring world leaders to take
meaningful action on global warming at upcoming United Nations climate
talks in Copenhagen. In San Francisco, a ride of 350 cyclists in
snorkels and flippers gathered at a downtown rally and traced a route
through Bay-side neighborhoods threatened by rising sea levels.
Critics of the movement say the goal of stabilizing the atmosphere
is too ambitious, and that even a cap of 450 parts per million would be
difficult to achieve with curbs on carbon emissions. But the heated
debate on the political possibilities of climate action is up against
cold, hard, science.
The head of UN’s Intergovernmental Panel on Climate Change, Rajendra Pachauri,
recently endorsed the goal of cutting emissions to 350 parts per
million or less. Pachauri, who in 2007 split the Nobel Peace Prize with
former Vice President Al Gore, was not able to advocate for any
specific goals as chair of the IPCC, “but as a human being I am
fully supportive of that goal. What is happening, and what is likely to
happen, convinces me that the world must be really ambitious and very
determined at moving toward a 350 target."