The first person to note the recent warming trend in Earth’s climate and associate it with fossil-fuel emissions was Guy Stewart Callendar (1898–1964). Callendar’s father, Hugh Longbourne Callendar, a professor of physics at the Imperial College of Science, London, had developed the platinum resistance thermometer, an instrument that permitted precise, continuous recording of temperatures. Guy Stewart Callendar worked as a steam engineer for the British Electrical and Allied Industries Research Association, but he had inherited his father’s interest in temperature measurement and, as a hobby, scrutinized weather records from around the world.
Callendar examined historical trends in global average temperatures by grouping temperature data from the most reliable weather stations in given regions of the world and weighting the importance of each group according to the geographic area represented by its stations.  He calculated 10-year moving averages (the average of the values 5 years before and 5 years after a given date) to smooth out year-to-year fluctuations. Callendar’s analysis suggested that world temperatures had increased by more than 0.2°C between 1890 and 1935. Based on crude measurements of carbon dioxide (CO2) concentrations in the atmosphere and a simplistic model, Callendar proposed that rising CO2 levels were responsible for over half of this warming.
The ideas of Callendar, an amateur encroaching on the domain of licensed professionals who focused on climate (climatologists), were not well received.  Most climatologists of the day believed that temperature data, because they were so variable, could be statistically manipulated to support nearly any conclusion. For example, Helmut E. Landsberg (1906–1985), perhaps the most renowned climatologist of the twentieth century , did not acknowledge any significant historical changes in global average temperatures and declared, “There is no scientific reason to believe that our climate will change radically in the next few decades, hence we can safely accept the past performance as an adequate guide for the future.” 
The larger scientific establishment also doubted whether atmospheric CO2 concentrations had changed significantly. Readings of CO2 concentrations would fluctuate with the winds because local sources that released CO2, such as nearby factories, and sinks that absorbed CO2, such as nearby forests, influenced every sample. The consensus of the scientific community was that nearly all the CO2 released from fossil-fuel burning would dissolve in the immense volume of Earth’s oceans, and thus atmospheric changes would be negligible.
 Callendar, G. S. (1938) The artificial production of carbon dioxide and its influence on temperature. Quarterly Journal of the Royal Meteorological Society 64:223-240.
 Baer, F. (1992) Helmut E. Landsberg. Memorial Tributes: National Academy of Engineering 5:153-158.
 Landsberg, H. (1946) Climate as a natural resource. The Scientific Monthly 63:293-298.
This is an excerpt from the book Global Climate Change: Convergence of Disciplines by Dr. Arnold J. Bloom and taken from UCVerse of the University of California.
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