People often ask: I want to get greener, what should I do? New light bulbs? A hybrid? A solar roof? Well, all of those things are helpful. But actually, the greenest thing you can do is this: Choose the right leaders. It is so much more important to change your leaders than change your light bulbs.

Why? Because leaders write the rules, set the standards and offer the tax incentives that drive market behavior across a whole city, state or country. Whatever any of us does individually matters a tiny bit. But when leaders change the rules, you get scale change across the whole marketplace. And the energy-climate challenge we face today is a huge scale problem. Without scale, all you have is a green hobby.

Have no illusions, everything George Bush wouldn’t do on energy after 9/11 — his resisting improved mileage for cars and actually trying to weaken air-conditioner standards — swamped any good works you did. Fortunately, the vacuum in the White House is being filled by leaders from below.

Take the New York City taxi story. Two years ago, David Yassky, a City Council member, sat down with one of his backers, Jack Hidary, a technology entrepreneur, to brainstorm about how to make New York City greener — at scale. For starters, they checked with the Taxi and Limousine Commission to see what it would take to replace the old gas-guzzling Crown Victoria yellow cabs, which get around 10 miles a gallon, with better-mileage, low-emission hybrids. Great idea, only it turned out to be illegal, thanks to some old size regulations designed to favor Crown Vics.