It remains to be seen if Obama, who took issue with the president calling climate change a "hoax", steps up his Trump shade game.
North American cities commit to tackle climate change in spite of the Trump administration.
Some 100 leaders were invited to what President Emmanuel Macron called the One Planet Summit in July, following Mr Trump's announcement that he would withdraw the USA from the agreement that has been signed by 197 countries and territories.
"President Obama will drop by the North American Climate Summit in Chicago this afternoon, where he will give brief remarks to thank the leaders gathered at the summit for their ongoing work to combat climate change", read a statement from Obama's spokeswoman.
Former U.S. President Barack Obama is expected to address the gathering of mayors from around the globe to discuss climate change.
Other mayors attending include Valerie Plante of Montreal and Miguel Angel Mancera of Mexico City. It applauded the more than 377 mayors from around the USA who have committed to the Paris Agreement in spite of that.
Paris Mayor Anne Hidalgo said city residents will be victims as a result.
The charter calls for mayors to achieve a per cent reduction in greenhouse gas emissions that's equal or more than outlined in the Paris agreement. He says mayors will sign a charter and discuss solutions including expanding access to public transportation.
"They're entitled to their own opinion, but not their own facts", he said.