The difference between research into co2 driven climate change then and now is a feature of Steve McIntyre at http://climateaudit.org/2013/07/26/guy-callendar-vs-the-gcms/
In 1938 Guy Callendar, employed as a 'steam technologist' by the British Electrical and Allied Industries Research Association wrote a paper that went straight to the Royal Meteorological Society (for various reasons) and has recently been unearthed by old timer bloggers. Callendar was an expert in steam and water vapour – the biggest component of the atmosphere. Read the link which is interesting from an historical angle as much as what Steve McIntyre brings to the table as a statistician. Basically, he is saying that by projecting Callendar's co2 methodology forwards in time, as opposed to the more complicated modern models which rely heavily on feedbacks (which involve the transport of water vapour into the atmosphere from the oceans) a more realistic view of how co2 might affect the global temperature is arrived at. It is noticeable that Callendar, who specialised in water vapour- visualised no such feedback mechanism that is inherent in the modern models – and make the predictions so high.