*This blog was originally posted to LACOASTPOST.com, an independent, interactive forum for an ongoing informed discussion of the status and future of the Louisiana coast. The mission of LACOASTPOST.com is to provide a real time venue in which to debate the current and projected state of our coast, including scientific, socioeconomic, fiscal and political issues.Three hundred fifty “350.” That’s the critical number that represents a safe climate. 350 means a stable civilization. It is the number we need to get back to and very soon because we are already at 387 and growing – well over the safe limit.But what is 350? Global warming pollution can be estimated by measuring the carbon dioxide concentration in the atmosphere in parts per million (ppm). Our civilization sprang up in the 270-290 ppm range and we have enjoyed a safe, stable level during the ten thousand years or so of the Holocene Epoch, since what is generally acknowledged as the dawn of agriculture and cities. But just over a hundred years ago, we started pumping carbon into the air at exponentially increasing rates, without a care in the world. Based on detailed analyses of ice cores through ancient glaciers we know that atmospheric carbon dioxide concentrations are higher now than at any time during the last 800,000 years!Climate experts have recently warned that there are dangerous tipping points that could be triggered if the 350 ppm threshold is exceeded much longer. Fossil fuels allowed the enormous advancement of our civilization – but not without a cost. Now the climate bill has come due and we must find a way to live within our means.350.org is a dynamic organization started by one of my heroes, Bill McKibben, noted writer, professor and political organizer. This talented man delivered the keynote address last week at the Tulane Law Evironmental summit, hosted by the Tulane Law School on April 3-5, an annual project totally managed by law students. According to Law Faculty Advisors Oliver Houck and Mark Davis, this year’s summit was exceptionally successful, with over 400 registrants, a dramatic increase from the previous average of about 150. Attracting speaker McKibben no doubt accounted for some of this success.McKibben wrote The End of Nature in 1989, the first book about climate change. Since that time he has continued a prolific writing career, including co-authoring a book with his colleague, Nobel laureate Al Gore. The keynote address lasted for well over an hour, keeping the packed hall spellbound. McKibben modestly described how he progressed from politically-naive climate change proselytizer living in the second smallest state (Vermont), to the grass roots organizer of a global movement that has exceeded his fondest hopes. He outlined the progression of his political education, including learning how to attract media attention by getting arrested.He told a wonderful anecdote about being invited several years ago by noted environmental activist Granny D Haddock to join a climate change protest at the US Capitol. They were both ultimately arrested and this man from Vermont, tall enough for the NBA, found himself bent over and handcuffed to this wonderfully feisty but tiny woman in her nineties.During his remarks McKibben suggested that our current atmospheric level of 387 ppm of atmospheric carbon is to Mother Earth what a similar level of blood cholesterol would be to a sedentary sixty-something smoker subject to swilling sweet drinks. There’s no question what the human patient would hear from her doc. Momma Earth would hear similar warnings from her climate doctor, “You are in grave danger of rising seas, severe weather changes, mass species extinctions, etc).”In fact our planet got its last major check up almost four years ago in Montreal in the form of the Kyoto Climate Accord (November 30, 2005). The prognosis at that time was bleak – carbon levels were rising rapidly with no end in sight. Clearly we have ignored the warnings; now the question is whether it is already too late to change our habits.Editor’s Note (Len Bahr): Another notable speaker at the summit was Mike Tidwell, author, Bayou Farewell, who has also gained broad recognition as a spokesperson for action on climate change. It was recently noted on LACOASTPOST.com that Tidwell was investigated during 2007 by the Maryland State Police under former Gov. Ehrlich for his radical activism on climate change.Watch the 350.org video here http://www.youtube.com/user/350org and pass it on. We need to keep 350 in our minds and in the email boxes of our representatives.SAVE THE DATE: October 24, 2009 is the date of an extraordinary global climate change initiative – October 24th 350 Action in New Orleans. Email me to get on the action list! email@example.comCasey DeMoss Roberts is the Special Projects Coordinator for the Gulf Restoration Network.