Following President Donald Trump's decision Thursday to pull the United States out of the historic Paris climate accord, Paris Mayor Anne Hidalgo encouraged him to reconsider what she called a "short-sighted" move.
"The years to 2020 will be crucial in determining if the worst effects of climate change can be avoided. American leadership on this urgent challenge is needed now more than ever," she wrote in an op-ed for Newsweek.
But even without the Trump administration's involvement, "the great cities of the world...remain resolutely committed to doing what needs to be done to implement the Paris Agreement," wrote Hidalgo
Subscribe to The World’s Most Powerful Women, Fortune’s daily must-read for global businesswomen.
And, like clockwork, after Trump announced the pull-out from the pact, dozens of mayors of U.S. cities published an open letter vowing to "adopt, honor, and uphold the commitments to the goals enshrined in the Paris Agreement."
The letter initially had 61 signatories but an updated version published late Thursday added another 21. The 82 leaders of cities from Seattle to New York to Fayetteville, Arkansas say they represent 39 million Americans.
"We will intensify efforts to meet each of our cities’ current climate goals, push for new action to meet the 1.5 degrees Celsius target, and work together to create a 21st century clean energy economy," says the letter that was posted by a group called Climate Mayors, which co-signer Los Angeles Mayor Eric Garcetti, former Houston Mayor Annise Parker, and former Philadelphia Mayor Michael Nutter founded to organize mayors against climate change.
To meet those goals, the mayors vowed to increase investment in renewable energy and energy efficiency, to buy and create more demand for electric vehicles, and to build on efforts to cut greenhouse gas emissions, create clean energy economies, and stand for environmental justice.
"And if the President wants to break the promises made to our allies enshrined in the historic Paris Agreement, we’ll build and strengthen relationships around the world to protect the planet from devastating climate risks," the letter reads.
"The world cannot wait — and neither will we."
One co-signer of the letter, Pittsburgh Mayor Bill Peduto, was especially vocal in pushing back against the president's decision on Thursday. Trump name-dropped the city in his speech, stating: "I was elected to represent the citizens of Pittsburgh, not Paris."
Peduto pointed out that Trump rival Hillary Clinton had actually won 80% of the vote in Pittsburgh in November and vowed that the city would support the principles of the Paris accord.
Paris's Hildago was quick to retweet him.