Air conditioners and refrigerators pose as big a threat to “life on the planet” as the threat of terrorism, Secretary of State John Kerry said Friday.

Kerry was in Vienna negotiating a global climate deal to phase out chemicals used as refrigerants in basic household and commercial appliances such as air conditioning and refrigerators, called hydrofluorocarbons, or HFCs. The chemicals are a potent source of greenhouse gas emissions that many scientists blame for contributing to global warming.