When President Carter donned a cardigan sweater and advocated conservation and environmentally friendly practices in 1977, he was savaged by critics and mocked by satirists. Thirty years later, the joke is on all of us and the governments are finally taking action.

To get an idea of how far the debate has come in just six years, think back to then-Spokane Mayor John Powers’ idea to put a rooftop garden atop City Hall. He was rewarded with relentless jokes for such an out of the mainstream suggestion. As it turns out, rooftop gardens are a smart way to control energy costs, quell the urban-heat-island effect, filter stormwater and scrub the air of carbon dioxide. A total of 522 mayors, including then-Mayor Dennis Hession, have signed the U.S. Mayors Climate Protection Agreement, which has a goal of reducing greenhouse gas emissions to 7 percent below 1990 levels by 2012.

Chicago, long known as a gritty city, has won numerous awards for its adoption of rooftop gardens, and, yes, its City Hall has one. In the summer, the temperature atop the building rarely gets past 90 degrees, while roofs on nearby buildings reach 160. Through its own planting and by offering incentives to businesses, the city boasts 2 million square feet of rooftop gardens. Plus, it has planted half a million trees since 1989.

The benefits go beyond mere symbolism, because buildings and houses in the United States consume nearly 40 percent of all energy and account for 30 percent of greenhouse gas emissions, according to the U.S. Department of Energy and the Energy Efficiency and Renewable Energy Network. By contrast, sport utility vehicles, minivans and light trucks account for 7 percent of energy consumption.

So the next time you vilify the owner of that gas-sucking Hummer, you might want to consider what’s leaking from your home. Have you replaced standard light bulbs with compact fluorescents? According to FastCompany.com, if every American household replaced just one traditional 60-watt with a compact fluorescent, it would save enough energy to light a city of 1.5 million people. Are you switching off your computer each night and unplugging your cell phone charger and other unused appliances? Have you donned a sweater and lowered the thermostat? How about increasing the insulation and checking the weather-stripping around doors and windows?

Because we waited so long, the urgency to act has grown. The combination of scarce energy supplies and climate change is no laughing matter. In moving forward, let’s look back to what Carter said 30 years ago:

“In the United States, our energy problems have the same cause as our environmental problems: wasteful use of resources. Conservation helps us solve both at once.”