Bill McKibben, founder of the 350.org campaign, took to the pages of the latest Mother Jones to offer a great primer on the Copenhagen climate conference. McKibben’s article is clear: the world needs to stabilize carbon dioxide in the atmosphere at 350 parts-per-million—the threshold of life on planet earth as we know it, according to scientists like James Hansen.

Problem is, the current atmospheric concentration of carbon dioxide is 387 ppm, which means we’ve already exceeded that threshold by a mile.

What on earth to do? The politically impossible. A simple statement in McKibben’s article leapt off the page and grabbed my attention: Getting to 350 ppm "would require focusing the entire planet for a generation on the task of transitioning off fossil fuel…It would mean aiming for a solution, not an agreement." To many, that’s a painful (perhaps unrealistic) argument, but that doesn’t make it any less true.

Right now, the best target coming from elected leaders (President Obama, e.g.) is 450 ppm, and it’s beyond wishful thinking to expect anything as ambitious as a 350 ppm target to come out of Copenhagen… we’ll likely not see a specific target at all.

That’s because politicians are terrible at doing hard things. There are too many influential power-players with money tied up in coal, oil and other fossil fuels—the germs of our planet’s poor health—for politicians to create policies and laws that make scientific sense.The political brain calculates what is possible and favors that over what is necessary.

But sometimes—and this is one of those times—we have to discover a way to make possible what is necessary. Sure, 450 ppm and beyond may be a more politically realistic goal, but if we don’t willingly make the necessary sacrifices to get to 350 ppm or below (quit burning fossil fuels), the planet will make other sacrifices for us (rising seas, droughts, disease, plummeting biodiversity…).

The real question is, what do we sacrifice by not taking this drastic action? Perhaps the planet, for one. But also a prize that even some unexpected Republicans intuitively understand is out there waiting to be claimed: technological and economic leadership in the energy sources of the future. Lindsey Graham (R-S.C.) recently said: "The green economy is coming. We can either follow or lead. And those countries who follow will pay a price. Those nations who lead in creating the new green economy for the world will make money."

Here’s how to make politicians listen: If the better part of a generation says they are not only willing to make the transition happen but demand that it be done, the necessary starts looking much more possible. That is the "work of a generation" McKibben refers to. The brightest minds and the mightiest muscle must be directed to creating this clean energy future. On our way to that future, we can hopefully wave at 350 ppm as we dive below it. The United States can lead or be led, and it’s up to all of us to make it happen.