Are fluorinated refrigerants needed - Will "natural" refrigerants suffice ?

This paper addresses the historical need for and introduction of fluorinated refrigerants to replace what were then largely “natural” refrigerants. It discusses the heretical question of whether there even are “natural” refrigerants, as contrasted to synthetic but nonfluorinated or more broadly nonhalogenated refrigerants. The paper outlines the successive refrigerant generations, with chemically delineated shifts, from nonfluorinated — use of which continues — to chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) to hydrofluorocarbons (HFCs) to unsaturated HFCs (hydrofluoro-olefins or HFOs) and probably also unsaturated HCFCs (hydrochlorofluoro-olefins or HCFOs). It raises questions on long-term acceptability of them. It briefly explores whether improved manufacturing of components and equipment for air conditioning and refrigeration systems changes matters. The paper concludes that different needs will require continued use of both nonhalogenated options (notably ammonia, hydrocarbons, and carbon dioxide) and halogenated options with demand for improved efficiency from both.