Former President Barack Obama will speak to dozens of mayors and leaders from around the world Tuesday as they prepare to sign what's being called a "first-of-its-kind global agreement on climate change" in Chicago.
Despite Trump's unwillingness to participate until the agreement is renegotiated, individual American companies - along with U.S. states and cities - have stepped up their commitment to the deal.
Obama told the audience that American voters should "make it a prerequisite" to vote for elected officials who say they are paying attention to global warming.
"And cities and states and businesses and universities and nonprofits have emerged as the new face of American leadership on climate change".
Obama also urged mayors in attendance, including Chicago's Rahm Emanuel, to continue efforts to combat climate change.
Obama ratified the Paris agreement in 2015, and President Trump said in June that the US would pull out of it. Syria recently said that it planned to join the accord, making the USA the only nation in the world that doesn't belong to it, which Obama said is a "difficult position to defend". The U.S. won't technically back out until 2020 because of legal technicalities.
"You may withdraw", says Emanuel, referring to Trump pulling out of the Paris Agreement.
Chicago is pursuing policies that will require large buildings to track and disclose their energy consumption, put more electric cars in the city's fleet, power all municipal buildings with renewable energy, and expand the environmental protection unit within the city's Department of Public Health.
Discussions will also devise concrete actions related to UNESCO's Declaration of Ethical Principles in Relation to Climate Change which outlines globally-agreed ethical principles that should guide decision-making and policy-making at all levels and help mobilize people to address climate change.
He says 51 mayors will sign a charter and discuss solutions including expanding access to public transportation.
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.
"Climate change can be solved by human action", he said.
Some environmental activists say that the mayors deserve credit for trying to pick up the slack from the Trump administration on reducing carbon emissions.
Paris Mayor Anne Hidalgo said city residents will be the victims if action isn't taken.
"We met resistance every step of the way", he said, according to The Hill.