President Donald Trump said he represented "the citizens of Pittsburgh, not Paris," when he withdrew this week from the historic climate agreement signed in the French capital. But Pittsburgh plans to step up its efforts to meet the climate goals the president has repudiated. Pittsburgh Mayor William Peduto responded to Trump's statement with an executive order recommitting the city government to its goals of cutting energy use by half and getting all its energy from renewable sources by 2030. With the federal government stepping away from climate action, the burden falls to American state and city governments and the private sector to curb greenhouse gas emissions. They've already been doing it, experts note. And many are now pledging to do more. A growing list of mayors, governors and businesses are pledging to step up their actions so the United States will meet the commitments it agreed to in Paris in 2015. However, experts say it's unclear whether they actually can fill the gap left by the Trump administration. Federal laggards "Over the past decade, the U.S. has led the world in emission reductions and our federal government had very little to do with it," said former New York Mayor Michael Bloomberg. "It happened because of leadership from cities, public opposition to coal plants, and market forces that have made cleaner sources of energy — including solar and wind — cheaper than coal," he said. Bloomberg was in Paris on Friday, announcing the formation of America's Pledge, a group that will submit to the United Nations a plan for how the United States will meet its Paris commitment, even without the federal government. Three states, 30 cities and 300 companies have signed on to the group so far, according to Bloomberg adviser Carl Pope. "The fact that the president of the United States no longer intends to cooperate with the Paris commitment doesn't mean the United States won't keep its word," Pope told VOA. States back renewable energy Though the Trump administration is rewriting federal rules limiting power plant emissions, 29 states require electric utilities to generate a portion of their electricity from renewable sources. Both Republicans and Democrats support the policies. This year, Maryland's Democratically controlled state legislature raised the state's renewable requirement, overriding the veto of the Republican governor. On the other hand, late last year, Ohio's Republican governor vetoed the Republican legislature's freeze of that state's renewable requirement. One market-based option for limiting emissions, known as cap and trade, lets polluters trade emissions allowances under an overall limit on such emissions. A cap-and-trade plan failed in Congress in 2010. But California and nine East Coast states have such programs, and the Regional Greenhouse Gas Initiative that includes those nine states is considering tightening the program. Mayors step in As of late Friday, nearly 200 mayors had signed a pledge to increase their efforts to cut greenhouse gas emissions. Among them was Stephen Benjamin, mayor of Columbia, South Carolina. "Even if the president follows through on his commitment to withdraw from the Paris Agreement, mayors will stand in the gap," Benjamin told VOA. Columbia has already been aggressively installing solar panels and working to reduce energy consumption, the mayor said, and the city is planning to convert its largest wastewater treatment plant to solar energy. Benjamin is vice president of the U.S. Council of Mayors. When the group meets in Miami this month, Benjamin will present a resolution urging city governments to commit to getting 100 percent of their energy from renewable sources by 2035. States' rights, federal funds White House spokesman Sean Spicer said other levels of government should feel free to pursue their own course. "We believe in states' rights," Spicer said. "If a locality, municipality or state wants to enact a policy that their voters or their citizens believe in, then that's what they should do." But the Trump administration's budget would undermine their efforts to act on climate, according to Georgetown University Climate Center Executive Director Vicki Arroyo. Trump's budget proposal calls for deep cuts to energy efficiency and renewable energy programs at the Department of Energy and the Environmental Protection Agency, including grants to state and local governments. The administration says that "more of this work should be done by the states," Arroyo noted. "And yet some of those sources of funding that enables that good work is cut. That's where the concern is." Mind the gap The cities and states pledging deeper cuts to greenhouse gas emissions represent roughly one-fifth of the nation's total, according to the research group Climate Interactive. "Alone, those certainly aren't enough to deliver the Paris pledge," said co-director Elizabeth Sawin. But Sawin said she expected more cities, states and companies to announce additional actions. Bloomberg adviser Pope notes that the United States has already achieved half of the emissions reductions it promised in Paris. He said he was "quite confident" the rest would come.