By exiting the Paris climate agreement, President Donald Trump says he sought to escape an economic straitjacket that would hinder him from making good on his populist campaign promises and pro-growth agenda.

Elected in no small part thanks to voters in "rust belt" industrial and mining states, Trump pledged as a candidate to breathe new life into traditional sectors like auto manufacturing, steel and coal mining.

He also sought to promote US oil and gas production, which has boomed thanks to the rise of hydraulic fracturing in shale.

It was no accident that Trump in his announcement Thursday said he had been elected to represent the "citizens of Pittsburgh, not Paris"

That city in Pennsylvania -- a state which went narrowly for Trump in November and helped tip the election in his favor -- is an old industrial stronghold where steel and railroad magnate Andrew Carnegie began his empire in the 19th century.

But the example was perhaps poorly chosen. US Steel, which was partly formed with Carnegie's assets, is now only the 11th largest employer in Pittsburgh, and Democratic Mayor Bill Peduto responded to the comment by pledging to adhere to the Paris agreement's objectives, in spite of Trump.

- Green economy -

Trump cited a study by NERA Economic Consulting, which said the Paris agreement "could cost America as much as 2.7 million lost jobs by 2025," including 440,000 jobs in the manufacturing sector.

He did not cite older statistics from the Commerce Department's Bureau of Economic Analysis, which in 2013 estimated there already were 3.5 million "green" jobs in the American economy.
And according to the International Renewable Energy Agency, in 2016, 777,000 people in the United States worked in renewable energy alone, not including hydropower, while job growth was 17 times greater in the sector than for the economy as a whole.

In his announcement, Trump said the Paris deal would add too many constraints to US businesses, especially in energy.

But the decision to exit the Paris agreement was swiftly denounced by the major American companies, including industrial and energy corporations, which have been working for years to reduce their carbon footprints.

"America first" has been Trump's catchphrase, and he said the climate pact put the country at "a very, very big disadvantage" even though the US already had the world's "highest standard of environmental protection."

He pointedly did not say that the United States was the world's second largest carbon emitter after China. 

The agreement calls for contributions from rich countries to help poor countries switch to sustainable energy. But Trump said Washington will not contribute, pointing to the $20 trillion US sovereign debt and saying some cities "cannot hire enough police officers or fix vital infrastructure."

There again, he left out the fact that the United States is the world's largest economy, with 25 percent of global GDP, with an unemployment rate that, as of Friday, was at a 16-year low of 4.3 percent.

- Dismantling a legacy -

Sticking with the Paris agreement could have meant accepting the very things Trump has rejected elsewhere: he has denounced or pledged to renegotiate free trade agreements, claiming they too put the United States at a disadvantage.

Trump also has set about dismantling the legacy of his predecessor Barack Obama, on policies from healthcare to environmental protection, and he has launched a major deregulation push.

Yet much of Trump's domestic agenda so far has met with considerable frustration. He is struggling to get a replacement for Obama's health insurance program through Congress. 

His tax plan for the moment remains a policy abstraction, and his administration is bogged down in investigations of possible collusion with the Russian government.

But exiting the Paris agreement required no act of Congress and allowed him to claim victory and say he was making good on promises to the American people.