Raising the bar for municipalities across the country, San Diego on Tuesday adopted one of the nation’s most ambitious plans to cut carbon emissions.

And in one aspect, the city’s document goes further than the historic climate change deal forged Sunday by world leaders gathered in Paris: It creates legally binding mandates for reducing levels of greenhouse gases.

“Today, San Diego took a landmark step toward securing a greener and more prosperous future,” Mayor Kevin Faulconer said in a statement.

The City Council unanimously approved the co-called Climate Action Plan, which requires annual emissions be cut in half during the next two decades based heavily on a strategy to use 100 percent renewable energy within that same timeline.

If the city doesn’t follow through on its promise to fight climate change, environmental groups and even the state attorney general could file lawsuits to force elected officials to comply.

“We have a lot to celebrate, and when we finish the happy dance and the kumbaya, we have to accept that the hard work now begins,” City Councilwoman Marti Emerald said at the meeting. “Just passing this doesn’t suddenly make everything better.”

Several environmental advocates warned at Tuesday’s meeting that they were ready to use legal action if necessary.

“Obviously, we aren’t going anywhere. We’re just getting started,” said Nicole Capretz, executive director of the Climate Action Campaign.

“The 100 percent [renewable energy] goal is a mandate,” she added. “It’s not dream. It’s not a wish or an aspiration. It’s a legal commitment.”

CLIMATE ACTION PLAN: KEY BENCHMARKS *Use 100 percent renewable energy citywide by 2035. *Cut vehicle trips in designated transit areas by 20 percent within next five years and by 50 percent within two decades. *Boost the urban tree canopy by 15 percent in five years and by 35 percent within two decades. *Recycle or compost 75 percent of all solid waste within five years and by 90 percent within two decades. *Increase zero-emission vehicles in city government’s fleet to 50 percent in five years and 90 percent within two decades.

The plan aims to satisfy state mandates for reducing greenhouse gases that have been rolled out during the past decade, including a requirement to cut emissions by 20 percent below 1990 levels by 2020, 40 percent by 2030 and 80 percent by 2050.

With ratcheting pressure from leaders in Sacramento and the courts, other cities in California may face increasing pressure to adopt similarly binding climate plans. Besides San Diego, Sacramento is currently the only other city in the state with enforceable mandates on this issue.

“The majority of [climate plans] in California do not meet this standard, and therefore, in my opinion, are legally challengeable,” said Chandra Slaven, a planning consultant who worked with San Diego on its climate plan starting in 2010. “All it takes is one lawsuit and they’re in trouble.”

Earlier this year, the state Supreme Court created a significant precedent when it declined to hear an appeal by the county of San Diego, which had tried to fend off legal challenges to its own climate action plan. Under a case brought by the Sierra Club, the county will now be forced to redraft its climate plan with enforceable measures for curbing emissions.

“I think smaller cities aren’t going to have to deal with this, but larger cities have definitely been put on notice because they’re going to be used as the example,” Slaven said.

“[Los Angeles] Mayor [ Eric] Garcetti is realizing that,” she added. “I would not be surprised if they went back and redid their climate action plan, particularly in light of San Diego.”

To make sure San Diego stays on track to hit its emissions targets, yearly monitoring reports prepared by city staff in collaboration with consultants will measure the impacts of each strategy laid out in the plan.

Upcoming targets include: boosting the urban tree canopy by 15 percent by 2020 and 35 percent by 2035; recycling or composing 75 percent of all solid waste by 2020 and 90 percent by 2035; and cutting car trips in key transportation areas by 20 percent by 2020 and 50 percent by 2035.

Urban planning and environmental experts said ushering in most of these changes should be fairly straightforward, but that’s dependent on political will at City Hall. They also said the technology already exists to meet these benchmarks — and to monitor whether specific programs result in carbon reductions.

The most controversial decision could be whether to implement community choice aggregation, or CCA, a program that would take control away from the local electric utility when deciding how much renewable energy a city uses.

However, when it comes to meeting San Diego’s transportation goals, elected officials may face an even more complicated puzzle. With vehicle emissions representing more than half of the city’s greenhouse gases, the newly minted Climate Action Plan will fail if residents don’t significantly cut back on the number of miles they drive.

In October, the San Diego Regional Association of Governments adopted a countywide transportation plan that included millions in infrastructure spending for the city of San Diego. While some of that money went to creating bike lanes and expanding the trolley network, funding was also allocated for widening nearly every major freeway in the city.

While SANDAG’s regional plan will likely be revised during coming years, the agency’s data shows the current proposal dramatically undercuts the city’s efforts to get people out of their cars.

“I think the issues with anything related to transportation is the city doesn’t have full control over that,” Slaven said. “So that’s going to take a great level of coordination and communication between the city and SANDAG.”

Like the county, SANDAG is facing a legal challenge for failing to heed state guidelines for reducing greenhouse gases. In the case, which is pending before the state Supreme Court, the Cleveland National Forest Foundation sued the agency for failing to analyze the state’s required long-range emissions reductions in its regional transportation plan.

The foundation won the first two rounds of the litigation, and SANDAG appealed it to California’s high court.

joshua.smith@sduniontribune.com / (619) 293-2234 / Twitter: @jemersmith