In an open letter to the international community on Monday titled We Are Still In, 1,219 governors, mayors, businesses, investors and American colleges and universities declared they would "continue to support climate action to meet the Paris Agreement".
It was yet another rebuke to President Donald Trump's decision last week to withdraw from the global accord designed to cut the emissions of gases - principally carbon dioxide - that drive global warming.
In the letter, the signatories said Mr Trump's decision "undermines a key pillar in the fight against climate change and damages the world's ability to avoid the most dangerous and costly effects of climate change".
"It is also out of step with what is happening in the United States," added the letter, signed by Google, Dropbox, Acer, Adidas, Eagle Creek, Facebook, Microsoft, Starbucks and others.
"In the US, it is local and state governments, along with businesses, that are primarily responsible for the dramatic decrease in greenhouse gas emissions in recent years," the letter stated.
Climate actions at the local and state levels and by businesses would multiply and accelerate in the years ahead, no matter what policies Washington might adopt, it said.
The Rhodium Group, a consultancy, has estimated that by the end of last year, US carbon emissions from energy consumption were 13.7 per cent below 2005 levels.
President Trump has sworn to revive the coal mining sector and said "millions" of jobs would be lost if the US stuck to its Paris Agreement commitments on curbing emissions principally from burning fossil fuels such as coal.
WHERE THE REAL ACTION IS
It's a big deal... The federal government provides a framework but the real action is in cities and municipalities. They are saying it makes sense, it is profitable, it is what citizens want.
MR ROGER-MARK DESOUZA, director of population, environmental security and resilience at the Wilson Centre in Washington.
Analysts said abandoning Paris climate targets and lifting environmental regulations would slow the reduction in emissions. But they are optimistic about the backlash to Mr Trump's decision.
There has been an uptick in recent months of a few thousand jobs in coal mining, but coal as an industry has been declining.
The US Energy Information Administration's data from nine north-eastern states, including New York, showed a dramatic shift in the past 10 years with coal-fired electricity generation falling from 31 per cent to 11 per cent of the energy mix, and cleaner natural gas nearly doubling its share.
A January Department of Energy employment report said the solar energy industry alone employed 374,000, while coal, oil and natural gas power plants accounted for 187,117 workers.
Mr Roger-Mark DeSouza - director of population, environmental security and resilience at the Wilson Centre in Washington - said that at the very least, Mr Trump has "spurred nationwide dialogue and discussion on the importance of climate to the US interest".
Surveys showed a majority of Americans favour action to curb climate change. A new Pew Research Centre survey found that 83 per cent of Americans say increasing use of renewable energy sources is a top or important priority.
In an interview with National Public Radio last weekend, Mr James Brainard, the Republican mayor of the town of Carmel in the state of Indiana, detailed exactly what mayors can achieve.
The city had switched almost all street lights to LEDs, getting a 22 per cent return on investment through lower electricity costs; created 405ha of parkland; and through traffic reorganisation and walking zones reduced the amount of time residents spend driving in their cars.
Mr DeSouza told The Straits Times: "It's a big deal."
He said: "The federal government provides a framework but the real action is in cities and municipalities. They are saying it makes sense, it is profitable, it is what citizens want."