What’s the best metaphor for the task of fighting global warming? I was on a panel on Sunday at Harvard’s Social Enterprise Conference where, in an effort to convey the scope of the job ahead, Dr. Paul Epstein of Harvard’s Center for Health and the Global Environment said the government’s effort to tackle climate change needs to be as ambitious as the Manhattan project, the Marshall plan and the Apollo moon program, all rolled into one.

Paul is truly an expert on climate change, and he says that we’ll have to reduce GHG emissions by 60 – 80% over the next decade or two if we want to stabilize CO2 concentrations in the atmosphere. Whatever the numbers turn out to be, he says, dealing with the problem will ultimately require a radical makeover of the global economy, transforming transporation, housing, land use, agriculture and the like.

By contrast, the Rev. Richard Cizik of the National Association of Evangelicals likened climate change to the civil rights movement of the 1950s and 1960s. Climate change, he says, is a moral issue, and those who end up on the wrong side of history will be judged harshly.

Both may be right. Slowing down the pace of global warming will require sacrifices, as well as more political will and courage than we’ve seen in a long time in Washington. It may take a mass movement to get us there. I wonder: If climate change is not the great moral issue of our time, what is?