The great climatologist Guy Callendar died in 1964, so I will briefly sketch some major developments in theories of climate change and global warming since then.
Although climate sceptics have abounded since, the reality of global warming has in reality been firmly established today. This has been reinforced by the scientific analysis of such factors as: change in ocean temperatures, deep sea cores, cycles of planetary change and atmosphere, melting of ice caps and glaciers, rising sea levels.
Calculations showed that a doubling of CO2 levels would cause roughly 2 degrees rise in world temperatures. Symptoms include more extreme events, such as droughts, bushfires and floods, heat waves and unusually cold conditions. We see all this depressingly on the news every day, combined with high death rates and massive waves of refugees and distressed.
Encouragingly, these developments have been much studied by international organisations such as the UN, NATO, the World Meteorological Organisation, and the Intergovernmental Panel on Climate Change (IPCC) which was set up in 1988.
I recommend reading such as Spencer Weart, The Discovery of Global Warming (1908).