Zohran Mamdani, the Democratic nominee, has vowed to strictly enforce the measure, Local Law 97, which calls for potentially expensive upgrades to buildings to curb greenhouse emissions.

Although in recent months Mr. Mamdani’s affordability agenda has eclipsed his stances on global warming and Local Law 97, the subjects are crucial to his platform because they are interconnected, said a spokeswoman. “Climate change is one of the most pressing issues facing New Yorkers, and it’s hitting working-class communities the hardest,” she said.

In New York City, buildings are responsible for about 70 percent of greenhouse gas emissions, which contribute to global warming. Local Law 97 targets about 50,000 properties that are larger than 25,000 square feet, calling for a series of reductions in emissions over the upcoming years. To meet the deadlines, some properties may have to take expensive steps like replacing oil-burning boilers or installing solar panels.

Mr. Mamdani has said that he would offer financial assistance to middle-income homeowners seeking to get into compliance with the law. The other candidates expected to take part in the Nov. 4 general election, which include Mayor Adams, favor some leniency in the implementation of Local Law 97.