Every ton of carbon dioxide pollution causes around $20 of damage to economies, ecosystems and human health. That sum times 20 implies $400 worth of damage per American per year. That’s not damage you’re going to do in the distant future; that’s damage each of us is doing right now. Who pays for it?

We pay as a society. My cross-country flight adds fractions of a penny to everyone else’s cost. That knowledge leads some of us to voluntarily chip in a few bucks to “offset” our emissions. But none of these payments motivate anyone to fly less. It doesn’t lead airlines to switch to more fuel-efficient planes or routes. If anything, airlines by now use voluntary offsets as a marketing ploy to make green-conscious passengers feel better. The result is planetary socialism at its worst: we all pay the price because individuals don’t.

It won’t change until a regulatory system compels us to pay our fair share to limit pollution accordingly. Limit, of course, is code for “cap and trade,” the system that helped phase out lead in gasoline in the 1980s, slashed acid rain pollution in the 1990s and is now bringing entire fisheries back from the brink. “Cap and trade” for carbon is beginning to decrease carbon pollution in Europe, and similar models are slated to do the same from California to China.

Alas, this approach has been declared dead in Washington, ironically by self-styled free-marketers. Another solution, a carbon tax, is also off the table because, well, it’s a tax.

Never mind that markets are truly free only when everyone pays the full price for his or her actions. Anything else is socialism. The reality is that we cannot overcome the global threats posed by greenhouse gases without speaking the ultimate inconvenient truth: getting people excited about making individual environmental sacrifices is doomed to fail.

High school science tells us that global warming is real. And economics teaches us that humanity must have the right incentives if it is to stop this terrible trend.

Don’t stop recycling. Don’t stop buying local. But add mastering some basic economics to your to-do list. Our future will be largely determined by our ability to admit the need to end planetary socialism. That’s the most fundamental of economics lessons and one any serious environmentalist ought to heed.