President Donald Trump pointed to Pittsburgh as a reason for pulling out of the Paris climate accord, but some residents in the former steel town are calling him rusty and out-of-date.

"Trump has no clue re Pittsburgh," wrote former Pennsylvania Governor Ed Rendell on Twitter. "It transformed itself by cleaning its environment. It went from old industrial city to high-tech mecca!"

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That's a transformation witnessed by anyone born before 1980, when the mills still spewed out smoke and flames along the rivers and the Carnegie Museums -- founded by steel tycoon Andrew Carnegie -- appeared to be constructed of black stone. When their exterior was cleaned of years of accumulated soot in the 1980s, many residents were surprised to see light-colored stone.

Pittsburgh has changed beyond its exteriors, though. The one-time industrial center is now a thriving city focused on health care, tech and clean energy. In fact, Pittsburgh now has more jobs tied to clean energy than to steel. Mayor Bill Peduto has taken to news programs and Twitter to denounce Mr. Trump's decision.

"As the Mayor of Pittsburgh, I can assure you that we will follow the guidelines of the Paris Agreement for our people, our economy & future," Peduto wrote.

As the Mayor of Pittsburgh, I can assure you that we will follow the guidelines of the Paris Agreement for our people, our economy & future. https://t.co/3znXGTcd8C — bill peduto (@billpeduto) June 1, 2017

As Peduto noted, the future of Pittsburgh isn't in coal or steel, an industry whose decline in the late 1970s and early 1980s created some painful years for the city.

The regional economy hit an unemployment rate of 18.2 percent in early 1983, compared with the then national rate of 10.5 percent, according to the University of Pittsburgh. The number of jobless workers in the area had swelled from 88,500 to more than 212,000.

Change didn't come quickly or easily, but the city slowly refocused on a few strengths, including technology and health care. Key to its reinvigoration were two institutions: Carnegie Mellon University and the University of Pittsburgh Medical Center.

Clean energy is part of that revival. More than 13,000 people now work in renewable energy and related areas in Pittsburgh, according to a report from the Keystone Energy Efficiency Alliance and Environmental Entrepreneurs.

Google (GOOG) and other tech companies have set up hubs in Pittsburgh, fueled by graduates of Carnegie Mellon and other local universities, while Uber picked the city as a test site for self-driving cars. In survey after survey, Pittsburgh is named as a top destination for workers and those seeking to combine an affordable cost of living, cultural offerings and a strong support of sports.

"[Trump] is sadly misinformed if he thinks we're nostalgic for the smoky city days of the past," Rachel Filippini, executive director of Group Against Smog and Pollution, told the Pittsburgh Post-Gazette. "The Pittsburghers I know want clean air and water, good jobs in a green economy, and a sustainable and healthy future for their children."

That's not to say Pittsburgh doesn't have challenges. Given the importance of health care to its economy, a repeal of the Affordable Care Act could pose a threat. The city's population is holding steady at slightly more than 300,000, but it hasn't yet shown the type of population growth that would replace the tens of thousands of residents who moved away in the last few decades.

Yet citing Pittsburgh as a reason to step back from the global climate change accord is striking local businesses and unions as backwards. Even steelworkers voiced their disapproval. United Steelworkers President Leo Gerard said in a statement the decision is "an inexcusable blow to the U.S. economy."