Guy Stewart Callendar (1897-1964), a British steam engineer, was the first scientist to study climate change in a rigorous and systematic way and the first to empirically connect rising carbon dioxide (CO2) concentrations in the atmosphere with the increase in the Earth’s temperature. In 1938, Callendar published a paper titled The Artificial Production of Carbon Dioxide and its Influence on Temperature, the first of many articles on the subject. He noted a significant upward trend in temperatures for the first four decades of the 20th century and a continuously rising concentration of atmospheric CO2 since post-industrial times. He linked these trends to the combustion of fossil fuels, describing it as an enhanced "greenhouse effect" where infrared radiation is both absorbed and emitted by the extra CO2, causing warming at the Earth's surface. For decades, scientists ignored, criticized, or downplayed Callendar’s work, yet research in the 1990s proved his early work to be surprisingly accurate considering the level of data monitoring available in the early 1900's.
- American Institute of Physics. The Discovery of Global Warming: The Carbon Dioxide Greenhouse Effect.
Fleming, James Rodger. 2007. The Callendar Effect. The life and work of Guy Stewart Callendar (1898-1964), the scientist who established the carbon dioxide theory of climate change. Boston: American Meteorological Society. ISBN: 1878220764
- New Dictionary of Scientific Biography. 2007. "Guy Stewart Callendar". Scribner's. ISBN: 0684313200
- Weart, S. R., 1997. The Discovery of the Risk of Global Warming. Physics Today, 50(1):34-40.