Scholars from ancient Greece to Fourier in the 18C, John Tyndall and Svante Arrhenius in the C19,, and since 1900, had debated the nature and causes of climate change they had observed (unsystematically). But it took a “weather nut”, Guy Callendar(1899-1964), first to identify that global warming had taken place by at least 0.5 degrees Celsius in the first three decades of the C20; and scientifically to identify expanding CO2 in the atmosphere from industrialisation as the likeliest culprit.

He estimated there had been a 10% increase in the concentration of CO2 between 1900 and 1938, the year he wrote a truly pioneering paper on the subject.

Callendar, who was a distinguished English steam and combustion engineer, a specialist in high steam temperatures and pressures, applied this knowledge to atmospheric heating. Always obsessive about collecting data (on railway engines for example), he painstakingly compiled weather statistics from around Britain and then the rest of the world, over many years. He not only showed global warming but effects such as the melting of glaciers. His theory was met with consternation and scepticism, but would be revived and expanded in a few decades time. Climate change is now recognised for the global crisis it it

For more details see James Rodgers Fleming, The Callendar Effect: The Life and Work of Guy Stewart Callendar …The Scientist Who Established the Carbon Dioxide Theory of Climate Change (2007).