This week, President Trump called for U.S. “energy dominance” and a ramping up of domestic coal, oil and gas production. But as Trump doubled down on fossil fuels, U.S. mayors voted in support of commitments to run their cities on 100 percent renewable power by 2035.

Civic leaders, both Republicans and Democrats, unanimously passed the resolution at a meeting of the U.S. Conference of Mayors in Miami Beach this week.

“Climate change may be the challenge of our generation, but it is also the opportunity of a lifetime,” said Mayor Philip Levine of Miami Beach, Florida. Mayors also approved resolutions calling on the federal government to commit to the Paris Agreement, enact the EPA’s Clean Power Plan — which cuts emissions from the power sector — and support the development of electric vehicle infrastructure, such as charging stations.

“We have to do our part to reduce our greenhouse gas emissions,” Levine said. According to the Sierra Club, if each of the 1,481 cities represented by the U.S. Conference of Mayors were to transition to 100 percent renewable electricity by 2035, U.S. power-sector carbon emissions would fall by 34 percent.

Setting a target is easy. Building new power plants and transmission line, revamping public policy, and beating back challenges from power utilities is much, much harder. In all likelihood, very few cities will manage to achieve that goal.

“There is more work to be done to realize this vision for our nation,” Steve Benjamin, mayor of Columbia, South Carolina, said in a statement. “Right now, all that matters is being done at the local level.”

To understand what it takes to generate to 100 percent clean power, look at Burlington, Vermont. The city gets more than half its electricity from hydropower and biomass — meaning a power plants that burns wood instead of coal or gas. Biomass is considered renewable because new trees will replace those that were incinerated, and they will scrub carbon pollution from the air and turn it into leaves and branches. Less than half of Burlington’s power comes from variable sources of energy like wind and solar.

San Diego, meanwhile, is aiming for 100 percent renewable power by 2035, but it is a much larger city, and it lacks the rivers and forests needed to run hydroelectric dams and wood-fired power plants. San Diego will source much of its electricity from wind and solar, meaning it will need to invest in energy storage, to keep the lights on after the sun sets or the wind dies down. The high cost of batteries makes this a more daunting task. Some experts don’t think it’s possible with existing technology.

There is still value in setting an ambitious target for renewable energy. The goal that will inform policy decisions, and it will provide a useful benchmark for measuring progress. In a time of federal inaction on climate change, states and cities are forging ahead. After Trump pulled out of the Paris Agreement, more than 330 cities pledged to fulfill the terms of accord.

In speech to mayors Saturday, former President Bill Clinton praised cities for their commitment to Paris. “You can get out of it or in it, but the water’s gonna keep rising,” he said. “Politics has almost no influence on science, in case you haven’t noticed.”

The local push to support Paris is not without precedent. When then-President George W. Bush refused to implement the Kyoto Protocol, a predecessor to the Paris Agreement, a coalition of mayors vowed to meet the goals of the treaty. Few succeeded. Even climate-conscious cities like Seattle fell short of the modest targets.

Currently, only 36 U.S. cities have formally committed to 100 percent renewable power, including including Columbia, SC, Salt Lake City, UT and San Jose, CA. The slate of resolutions on climate and energy from the U.S. Conference of Mayors encourage other cities to do the same.

“Cities don’t need to wait for Washington, D.C. to act in order to move the ball forward on clean energy,” said Michael Brune, executive director of the Sierra Club. “What better way to kick off Donald Trump’s energy week than with a message from our nation’s mayors that cities are ready for 100 percent clean and renewable energy.”

Jeremy Deaton writes for Nexus Media, a syndicated newswire covering climate, energy, policy, art and culture. You can follow him at @deaton_jeremy.