Donald Trump barely had time to leave a sun-drenched Rose Garden after announcing the US exit from the historic Paris climate change agreement before the backlash began.

The voluntary deal, aimed at curbing global temperature rise to under 2C, was “draconian” and would cause a “very diminished quality of life” for Americans, Trump said on 1 June last year. “I was elected to represent the citizens of Pittsburgh, not Paris,” the president added.

Almost immediately, Bill Peduto, the mayor of Pittsburgh, retorted via Twitter: “I can assure you that we will follow the guidelines of the Paris Agreement for our people, our economy & future.”

In the year since, an alliance of American cities, states and green groups have flung themselves at the gaping void left by Trump’s decision to remove the world’s second-largest carbon polluter from a deal aimed at preserving the livability of much of the planet. This coalition has experienced a bruising 12 months during which successes at a local level have been regularly overshadowed by an administration intent on tearing down any edifice of climate policy.

Pittsburgh is one of 405 municipalities representing 70m Americans that are signed on to the Climate Mayors initiative, which has blossomed in the past year. More than 80 US cities - some, like San Diego, run by Republicans - have committed to 100% renewable energy.

A broader group of several thousand businesses – including Amazon, Levi Strauss & Co and Google – cities and states have pledged to follow the Paris goals via the We Are Still In coalition, spearheaded by the billionaire former New York City mayor Michael Bloomberg and the California governor, Jerry Brown. Brown has attacked Trump’s “reckless disregard” for climate change and said California will launch its own climate-monitoring satellites if Republicans hobble Nasa’s science programs.

“The collective commitments of business and state governments have sent a powerful signal that they are not stepping into line with the federal government when it comes to their attitude to climate – and they must continue with determination,” said Helen Clarkson, chief executive of the Climate Group, which runs a 100% clean energy pact joined by companies such as Apple, Kellogg’s and Visa.

This backlash has spurred cities to quicken the pace in certain areas – New York is to electrify its bus fleet and Los Angeles has promised to abandon coal-fired electricity. New York has also vowed to divest from fossil fuels and is suing the world’s largest oil companies for their role in escalating sea level rise, heatwaves and natural disasters.



Meanwhile, states such as California and New Jersey have heightened targets to cut greenhouse gas emissions while ramping up solar and wind energy capacity.

Environmental groups, bolstered by a surge in donations after Trump’s election, have pushed for the retirement of US coal power plants, with some success – more than half of the coal facilities operating in 2011 have been earmarked for retirement, primarily due to strong competition from cheap natural gas.

“Trump was a momentum killer so the job now is to rebuild momentum,” said Bill McKibben, co-founder of the climate group 350.org. “It’s powerful to see cities and states stepping up. Global warming is the biggest thing humans have ever done and in a rational world we’d all come together to address it. But we don’t live in a rational world, so smaller entities are having to fill the gap.”

Still, the antipathy of the Trump administration towards climate action is taking its toll. US energy emissions are at a 25-year low due to trends in energy efficiency and the decline of coal. But at a juncture when far deeper emissions cuts are required to avoid 2C of warming, the US is in danger of stalling – by 2025, the US is set to achieve only half of the reductions it pledged in Paris, according to a new analysis.

The Trump administration threatens to overwhelm the defiance shown by cities and states by reversing vehicle emissions standards, loosening regulations around oil and gas drilling and working to scrap Barack Obama’s centerpiece clean power plan. Trump, who donned a coal miner’s helmet during the 2016 presidential campaign, has claimed he has “ended the war on beautiful, clean coal”.

Trump’s promise to withdraw from the Paris deal – which can’t become reality until November 2020 due to notice periods – hasn’t caused the agreement to unravel. But it has certainly shifted the international dynamics of the accord, despite the best efforts of US cities and states to provide a countervailing view.

“It’s good news that other countries haven’t walked away,” said Todd Stern, who led talks for the US in Paris. “The less positive part is that it has been very damaging for the US. In the absence of the US, we are seeing some countries try to pull back on what was agreed to in Paris. When you have the largest historical emitter not part of the deal, that is obviously not good.”

Last year the US was rattled by three savage hurricanes that caused record damages, serving as a sobering reminder that even if anti-Trump jurisdictions ameliorate the worst of the reversals, it may not be enough to stave off some punishing consequences.

“Everyone is doing their best but it’s not like there are levers of power to pull in Washington at the moment,” said McKibben. “The problem with climate change is that it’s a timed test. The physics of the planet aren’t in a holding pattern. You lose a few years and there goes an ice cap.”