Mayors from 51 cities including Paris, Mexico City, San Francisco and Phoenix attended the summit.
The need for greater cooperation among cities is evident by the environmental challenges they face, Steve Adler (D), mayor of Austin, Texas, said during the charter's signing ceremony.
"But the good news is that the Paris agreement was never going to solve the climate crisis on its own", Obama stated.
Technically, the US can't give notice of its departure from the non-binding agreement until November 2019 under terms agreed upon when the pact was negotiated in 2015.
Many big city American mayors pilloried Trump as being shortsighted. "And what that tells us is that climate is changing faster than our efforts to address it".
The Trump administration has made multiple decisions to end or reverse Obama-era policies focused on combatting climate change. Mancera says the city is trying to accelerate a transition to soot-free engines and procure zero-emissions buses by 2025 with an overall zero-emissions goal for most of the city by 2030.
Mayor Emanuel has continued to push his way forward in city sustainability and environmental protections. The president criticized the climate accord, which sets the goal of holding global warming below 3.6 degrees Fahrenheit, as an example of a deal " to the exclusive benefit of other countries".
Barrett said he would be discussing Milwaukee's action on climate change. "I'm calling on our businesses, utilities, Public Service Commission and state government to acknowledge the importance of climate change and work with us to plan and invest in solutions".
Former President Barack Obama is expected to address mayors from around the world at a Chicago summit to discuss climate change.
Dressed casually in a jacket but no tie, Obama was introduced by Emanuel, who was his first White House Chief of Staff and had invited him to speak for 15 minutes off the meeting's official agenda. In signing the charter, cities also commit to tracking and publicly reporting city emissions. Syria announced last month that it would join the accord, leaving the U.S.as once it can formally withdraw.
Former President Barack Obama is expected to address a gathering of mayors from around the globe convening in Chicago to discuss climate change after President Donald Trump said the USA will pull out of the Paris climate accord.
The preamble to the Chicago Climate Charter the participating mayors signed on Tuesday read: "President Trump's decision to withdraw the United States from the Paris Agreement spurred over 380 cities in the US, numerous cities in other parts of North America, and countless organizations worldwide to commit themselves to the Agreement".
Chicago Mayor Rahm Emanuel and a number of other mayors have signed onto the Chicago Climate Charter, committing to reduce emissions.