Air conditioning
Modern air conditioning emerged from advances in chemistry during the 19th century, and the first large-scale electrical air conditioning was invented and used in 1902 by US inventor Willis Carrier. The introduction of residential air conditioning in the 1920s helped enable the great migration to the Sun Belt in the United States.
Guy Stewart Callendar
Guy Stewart Callendar (; February 1898 – October 1964) was an English steam engineer and inventor. His main contribution to knowledge was developing the theory that linked rising carbon dioxide concentrations in the atmosphere to global temperature. This theory, earlier proposed by Svante Arrhenius, has been called the Callendar effect. Callendar thought this warming would be beneficial, delaying a "return of the deadly glaciers."