Complex sentence: Guy Stewart Callendar (Feb 1898-Oct 1964) was an English steam engineer and inventor, but whose main contribution to knowledge was propounding the theory that linked rising carbon dioxide concentrations in the atmosphere to global temperature.
Split into simpler sentences: Guy Stewart Callendar (Feb 1898-Oct 1964) was an English steam engineer and inventor. His main contribution to knowledge was propounding the theory that linked rising carbon dioxide concentrations in the atmosphere to global temperature.