The Obama administration signed onto a deal over the weekend with nearly 200 countries to combat global warming by phasing out the refrigeration chemicals used in air-conditioners, even as industry scrambles to find replacement chemicals needed to keep homes cool and food fresh.

Environmental Protection Agency Administrator Gina McCarthy, who was key in securing the deal, said the chemicals represent potent greenhouse gas emissions, called hydrofluorocarbons, or HFCs, that are causing harmful man-made climate change, and are thousands of times more potent than carbon dioxide.