“Just a sleep-deprived activist and organizer.” That’s how environmentalist Bill McKibben describes his current incarnation, with writing career in abeyance while he proselytizes about the danger of climate change. The plight he first wrote about as hypothesis in 1989 has evolved into “deeply rooted consensus.” By 1995, world climatologists agreed: “Human beings are heating up the planet.”

After the inflection point of the Industrial Revolution, McKibben reckons, “no surprise --stuff starts to happen!” That stuff is escalating atmospheric carbon. Fast forward to summer 2007, when “Arctic sea ice melted at an alarming pace.” Other deleterious effects he cites include permafrost reduction; growing release of greenhouse gas methane; paradoxical increase in both drought and deluge; rising sea level; wildfires and deforestation; agricultural jeopardy. These phenomena conspire in feedback loops to pose accelerating risks to civilization.

McKibben credits NASA climatologist Jim Hansen with deriving “the most important number in the world” – the tolerable carbon level allowing survival of life on earth, now recognized as 350 parts-per-million maximum. Trouble is, we’re already past that sustainability point, owing to rampant fossil fuel combustion. We face “not a problem for your grandchildren to solve…it’s a problem for your parents to have solved.”

Upon return to Vermont from a revelatory 2006 journey to Bangladesh, McKibben’s mission became activism in service to global warming awareness. He gathered 1,000 people on a five-day pilgrimage to spread the word. At the sight of this mass of humanity in a rural state, he says “cows were running in terror.” So began a populist movement demanding an 80% decrease in carbon emissions by 2050.

McKibben saw the way ahead as harnessing the Internet’s multiplicative power. In 2007, with the help of six students and email’s exponential impact, 1,400 simultaneous demonstrations took place countrywide. “The thing just went viral,” McKibben exclaims, “…the biggest day of grass-roots environmental activism since the first Earth Day in 1970.” Social networking and cell phones proved most effective tools for mobilization.

Organizers next turned their aims to the upcoming Copenhagen conference to form a treaty succeeding the Kyoto Protocol. The campaign is aptly titled 350.org. McKibben endorses the virtue of a simple number as a rallying point because “Arabic numerals are one of the very few things that translate easily around the world,” avoiding cross-cultural semantic mishaps.

From Martin Luther King, Jr., McKibben absorbed principles of righteous activism. The good fight must be “creative…determined…joyful.” In closing, McKibben cautions “nature does not grade on a curve.” Global warming “is the morally urgent question of our moment.”