THOMAS L. FRIEDMAN: And the Color of the Year Is ...

I know that you should never generalize about global warming from your own weather, but as a longtime resident of Washington, D.C., it’s hard not to, considering that it’s been so balmy this winter season I’m half expecting the cherry blossoms to come out for Christmas. In fact, my wife was rummaging through her closet the other day and emerged to tell me she needed a whole new wardrobe — “a global warming wardrobe,” clothes that are summer weight but winter colors.

For this, and other reasons, had I been editing Time magazine I would not have opted for the “you” in YouTube as Person of the Year — although that was very clever. No, I’d have run an all-green Time cover under the headline, “Color of the Year.” Because I think that the most important thing to happen this past year was that living and thinking “green” — that is, mobilizing for the environmental/energy challenge we now face — hit Main Street.

For so many years the term “green” could never scale. It was trapped in a corner by its opponents, who defined it as “liberal,” “tree-hugging,” “girly-man,” “unpatriotic,” “vaguely French.”

No more. We reached a tipping point this year — where living, acting, designing, investing and manufacturing green came to be understood by a critical mass of citizens, entrepreneurs and officials as the most patriotic, capitalistic, geopolitical, healthy and competitive thing they could do. Hence my own motto: “Green is the new red, white and blue.”

How did we get here? It was a combination of factors: Katrina, Al Gore’s terrific movie, the growing awareness that our gas guzzlers are financing the terrorists, preachers and rogue regimes we’re fighting, the real profits that major companies like G.E. and DuPont are making by going green, and the fact that even the Pentagon has given birth to “Green Hawks,” who are obsessed with powering our army with less energy.

The most telling sign was the last election, when “being green became pragmatic,” said the Democratic pollster Stan Greenberg. “No one thought that running an ad on alternative energy was something for an elite target audience anymore. The only debate we had was whether it was one of the three things a candidate should talk about or the only thing.”

And now, Wal-Mart. Wal-Mart has earned its black eyes for labor practices. But the world’s biggest retailer lately has gotten the green bug — in part to improve its image, but also because it has found that being more energy efficient is highly profitable for itself and its customers.

Wal-Mart has opened two green stores where it is experimenting with alternative building materials, lighting, power systems and designs, the best of which it plans to spread to all its outlets. I just visited the one in McKinney, Tex. From the big wind turbine in the parking lot and solar panels on key walls, which provide 15 percent of the store’s electricity, to the cooking oil from fried chicken that is recycled in its bio-boiler and heats the store in winter, to the shift to L.E.D lights in all exterior signs and grocery and freezer cases — which last longer and sharply reduce heat and therefore the air-conditioning bill — you know you’re not in your parents’ Wal-Mart.

Other big companies are now sending teams to inspect the green Wal-Marts, and customers are asking the manager how they can adopt these innovations at home.

“When I started having people stop me in the aisles and say, ‘How do I do that?’ or ‘Can I do that?’ that’s when we really started realizing that this isn’t just a small thing, this can be really large and can be very rewarding to the planet,” said the store’s manager, Brent Allen.

Hey, the more energy-saving bulbs Wal-Mart sells, the more innovation it triggers, the more prices go down. That’s how you get scale. And scale is everything if you want to change the world, but to achieve scale you have to make sure that green energy sources — biofuels, clean coal, and solar, wind and nuclear power — can be delivered as cheaply as oil, gas and dirty coal. That will require a gasoline or carbon tax to keep the price of fossil fuels up so investors in green-tech will not get undercut while they drive innovation forward and prices down. The U.S. Congress has to stop running from this fact.

Because while our embrace of green has finally reached a tipping point, the tipping point on climate change and species loss is also fast approaching, if it’s not already here. There’s no time to lose. “People see an endangered species every day now when they look in the mirror,” said the environmentalist Rob Watson. “It is not about the whales anymore.”