Palo Alto's next green program won't rely on tough energy standards or strict building codes but on hundreds of volunteer teams preaching the gospel of conservation to their friends and neighbors.

The City Council agreed on Monday by a 7-2 vote, with Vice Mayor Greg Scharff and Councilwoman Karen Holman dissenting, to join a small pool of cities vying to take part in the Cool Cities Challenge -- a three-year program that sets ambitious goals for carbon reduction and relies on widespread grassroots support to meet these goals.

The brainchild of Empowerment Institute, the challenge would launch at three California cities and at three neighborhoods of Sao Paulo, Brazil. It aims to draw participation from between 25 percent and 75 residents of each participating community. The goal for the participants would be to reduce the community's carbon footprint by 25 percent. The effort also aims to get at least 40 percent of the residents to retrofit their homes and to "stimulate green economic development around heightened demand for low-carbon goods and services."

In July, the council heard a presentation about the Cool Cities Challenge from David Gershon, CEO of the Empowerment Institute and author of the book "Low Carbon Diet," which offers tips for green living. These include turning off the car engine during stops longer than a minute; washing laundry loads with cold water; and hand-washing dishes if there isn't a full load for the dishwasher.

Other partners in the Cool Cities Challenge are the Lawrence Berkeley National Laboratory, World Wildlife Fund, Stanford University, University of California, Berkeley, and University of California, Davis.

Gershold told the council that the effort would entail engaging around 16 partner groups, including businesses and faith-based organizations, whose members and customers would be encouraged to organize the program on a block-by-block basis. Gershon called this the "whole system approach."

"It has to engage the whole set of civic groups, local businesses and local governments," Gershon said.

The point of the Challenge is to fully develop a program that could then be scaled up and spread to other parts of the country and the world. Palo Alto would be one of the "early adopter" cities. Other cities that have expressed interest in participating are Davis, San Rafael, Sonoma and a part of San Francisco.

With its vote Monday, the council authorized City Manager James Keene to sign a "letter of intent" signaling the city's interest in participating in the Challenge. The council majority agreed that the goal of the Cool Cities Challenge is consistent with the city's own commitment to carbon reduction and its history of sweeping green programs. These include the recent adoption of a carbon-neutral electric portfolio and PaloAltoGreen, a hugely successful program that allows utilities customers to pay extra to support renewable energy sources.

But while those programs, like most of the city's other green efforts, are top-down initiatives orchestrated from City Hall, the Cool Cities Challenge would lean heavily on residents. Participating cities would aim to achieve the carbon-reduction goals within three years.

"Part of the intention is to have a large-scale, community-wide, multi-year project aimed at changing behaviors and practices at a very direct personal household level that by its nature calls for a very sustained effort," Keene said.

Councilman Larry Klein was among those who spoke in favor of signing up for the Challenge. Klein said the city's existing green programs tend to target "low-hanging fruit" but do little to encourage changes in individuals' behavior. He acknowledged that getting an individual to change his or her behavior is a tall task, but said that the world will not meet its critical carbon-reduction goals without these sorts of changes.

"It may not succeed, but that doesn't mean we shouldn't try it," Klein said. "If it was that easy, everyone would be doing it without any problems."

Councilwoman Gail Price concurred and called the opportunity to participate "very exciting."

"This kind of a program really identifies and articulates a lot of the beliefs and values that we espouse," Price said. "It's a really critical opportunity."

Vice Mayor Greg Scharff disagreed and characterized the goals of the Challenge as unrealistic. Scharff said the Challenge will likely "distract from things that can actually get done." Getting more than 25 percent of the community to participate is an impossible task, he said, and even getting 15 percent to sign on would be a great accomplishment.

"I don't think the community will step up with those kinds of rates. It's not going to make sense at the end of the day," Scharff said. "I think this is too ambitious and too unlikely to occur, so I can't support this."

The letter of intent from Keene touts the city's "track record as an early adopter city," its "desire to take on big challenges," and its "can-do community culture."

The letter does not, however, guarantee that the city will participate in the Cool Cities Challenge. Fundraising for the Challenge is still in progress and cities will not formally apply until the funds are secured. Three cities would then be selected from the pool of applicants.