The C40 Cities Climate Leadership Group said Thursday at a conference in San Francisco that the cities saw emissions decrease at least 10 percent from their peak over a five-year period.
The UK is looking beyond our strong record on climate action at home.
But that is not the end of the road for the Global Climate Action Summit, the idea is to keep up the momentum. Going green is a must.
"This is real and we will take action even if Washington doesn't", said Los Angeles mayor Eric Garcetti.
Giuseppe Sala, the mayor of Milan, Italy, talked up plans to reduce waste from food and other sources.
"Would it be easier if the Federal government and Congress were our partner?"
In closing remarks, United Nations climate chief Patricia Espinosa also called for a new era of climate diplomacy that includes not just national governments but also cities and regional bodies as well as industries - an approach she dubbed "inclusive multilateralism".
In a speech, Bloomberg called the conference a way to broadcast that the U.S.is still committed to the cause.
The first ever Green Great Britain Week will be held from 15 October, created to highlight the opportunities that clean growth offers and raise awareness of how business and the public can tackle climate change.
Amid swirling uncertainty about the commitment of the United States to global climate action under the Trump administration, cities and businesses have banded together to push for support for the Paris Agreement under the banner "America's Pledge".
In 2015, 196 countries around the globe came together under the Paris Agreement to transform their development trajectories so that they set the world on a course toward sustainable development, aiming at limiting warming to 1.5 to 2 degrees Celsius above pre-industrial levels.
Bloomberg and Brown said they calculate the U.S.is within striking distance of the reduction in greenhouse gases it previously promised.
Trump announced a year ago that he was withdrawing from the landmark climate accord.
The legislation also marks the latest conflict between California and President Trump, with the state repeatedly defying the administration's policies on everything from energy to civil rights to immigration.
In response to a question Thursday at a news briefing, Brown, Democrat, said Trump will likely be remembered poorly when it comes to the environment.
"I think that this summit's been very useful", he said.
"I'm volunteering to attend the event trying to understand what everybody is talking about, how our decisions are made, who is making decision, who has the power to decide climate policy", she said.
The CEO of one of the world's largest online business software companies is urging fellow technology leaders to help fight climate change.
Jerry Brown (D) on Friday said his state is moving forward to launch its own satellite to monitor climate change sources in response to President TrumpDonald John TrumpTrump stands by tweets questioning Puerto Rico death toll: "NO WAY" Trump pushes back on ex-lawyer putting out book, cites "attorney-client privilege" Wealthiest Republican supporter in OH quits party MORE threatening funding for NASA's program.
Salesforce recently opened a 61-story office tower in San Francisco that the company says relies on clean energy to operate.