New York, Boston, and Washington, D.C. joined cities around the world in lighting their city halls green to show support for the Paris Agreement on climate change. Clockwise from upper left: Barcelona, Paris, Warsaw, Boston, Mexico City, New York. Credit: Courtesy / C40 Cities Climate Leadership Group

When U.?S. President Donald Trump announced his decision to withdraw his country from the Paris Agreement on climate change, he singled out one U.?S. city to make his case. “I was elected to represent the citizens of Pittsburgh,” he said. “Not Paris.”

The mayor of Pittsburgh was not amused.

“I’m appalled that the president used my city to justify his unacceptable decision, as most other Pittsburghers are,” Mayor Bill Peduto said in a statement on Thursday. “I was one of the nation’s mayors who went to Paris to fight for the accords, and my city, which has finally bounced back from decades of industrial carnage, will do all it can to promote its own environmental standards.”

Peduto’s was one of hundreds of verbal volleys criticizing Trump’s decision. But many leaders of U.?S. cities and states have been responding with more than words. Here are four ways they’re fighting back against Trump and showing that they’re ready to stick with the spirit of the Paris Agreement regardless of what Trump does.

1. Doubling Down on the Paris Accord

While national governments are the only official signatories to the Paris Agreement, part of what has given the accord global momentum is the voluntary commitments made by other actors. Cities are chief among them, with more than 2,500 municipalities pledging to take action in the effort to fight climate change since the agreement was negotiated in 2015.

Thursday afternoon, New York City Mayor Bill de Blasio reaffirmed that commitment with an announcement of an impending executive order “to honor the goals of the Paris agreement.” Already, the city has committed to reducing the Big Apple’s carbon emissions by 80% from 2005 to 2050.

The same day, the city council of Portland, Ore., passed a resolution to move the city to 100% renewable energy by 2050. That pledge has become the gold standard in the Pacific Northwest region of North America, led by Vancouver, which hosted a summit last month to help cities reach that ambitious target.

And in Pittsburgh, Peduto also issued an executive order reaffirming that the city’s climate plans remain in line with the Paris Agreement. In July, city leaders are expected to publish the third version of the Pittsburgh Climate Action Plan, which will likely one-up the city’s previous climate commitments. This effort to continually reach for more ambitious climate targets is keeping in line with the accord, whose premise is that countries will “ratchet up” their emissions reduction plans every five years.

2. Forming an Alliance of States

Just hours after Trump’s decision was made public, three U.?S. states with the largest economies  – California, New York, and Washington State – announced they are forming something called the United States Climate Alliance. While the exact function of the alliance remains unclear, a press statement released by Washington Gov. Jay Inslee made clear some of the pact’s intentions.

“New York, California, and Washington, representing over one-fifth of U.?S. Gross Domestic Product, are committed to achieving the U.?S. goal of reducing emissions 26-28% from 2005 levels and meeting or exceeding the targets of the federal Clean Power Plan,” the statement read. The Clean Power Plan was former U.?S. President Barack Obama’s emissions-reduction effort, which he brought to the table at the Paris talks that forged the climate agreement.

As one signal of how states might deliver on that promise, New York Governor Andrew Cuomo unveiled a  $1.65 billion investment in renewable energy, the largest single such procurement by a U.?S. state.

Since Thursday, the states of Connecticut, Delaware, Hawaii, Massachusetts, Minnesota, Oregon, Puerto Rico (a self-governing U.?S. territory), Rhode Island, Vermont, and Virginia announced they would join the alliance. These states all voted against Donald Trump in last year’s presidential election, although some have governors affiliated with Trump’s Republican Party, suggesting the alliance has bipartisan support.

Six other states – Colorado, Pennsylvania, Maryland, Montana, North Carolina, and Ohio – also have announced their intention to meet their goals under the Paris Agreement, although they have not formally joined the alliance. Three of these states voted for Trump last year. In addition, eight of these states are signatories to the Under 2 MOU. That’s a pledge by “subnational” governments around the world, initiated by California Gov. Jerry Brown, to take actions necessary to keep the world’s mean temperature from rising by more than 2ºC above pre-industrial levels by the year 2100.

3. Putting Money on the Table

In his announcement, Trump decried the money that the U.?S. pledged to implementing the Paris Agreement. A small part of that money would go to the U.?N. Framework Convention on Climate Change, the Bonn-based office that coordinates global implementation of the Paris Agreement.

In response to Trump’s announcement, Bloomberg Philanthropies, the charity arm of former New York City Mayor Michael Bloomberg’s vast fortune, pledged $15 million to make up the funding gap.

That amount, however, is relatively small compared to the $3 billion the U.?S. had previously pledged for the Green Climate Fund, which supports climate-related efforts in developing countries. The Obama administration had delivered only $1 billion by the time it left office in January, and Trump has signaled that he would zero out any future payments.

4. Standing in Solidarity

Trump launched his first salvo against U.?S. climate policy in March when he vowed to scrap the Clean Power Plan. At the time, the newly formed Mayors National Climate Action Agenda fired back, writing an open letter signed by 75 cities representing 42 million U.?S. residents.

That group, now calling themselves Climate Mayors, was at it again on Thursday. As of press time, 211 mayors have added their signatures to their latest missive, which reads in part: “We will continue to lead. We are increasing investments in renewable energy and energy efficiency. We will increase our efforts to cut greenhouse gas emissions, create a clean energy economy, 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.”

Already, mayors are showing a desire to turn this solidarity into action. In March, they told automakers they were ready to make huge investments in electric vehicles – provided that car manufacturers can meet their need for utility trucks, vans, fire trucks, and other vehicles more specific to municipal needs than private consumer preferences.

Gregory Scruggs is Citiscope’s Habitat III correspondent. He is a journalist who has focused on cities and culture, especially in Latin America and the Caribbean. He covered World Urban Forum 5, Rio...