In announcing the findings, the Berkeley Earth Surface Temperature (BEST) project spokespeople expressed some considerable surprise at the definitive nature of their results. Especially since the project was funded in a major part by organisations that would prefer the proof went the other way.
The project received funding of $US150,000 from the Charles G. Koch Charitable Foundation, a fund set up by the billionaire US coal magnate who is known as a significant supporter of the climate sceptic Heartland Institute think tank. In addition, the research was funded to the tune of $US100,000 from the Fund for Innovative climate and Energy Research, created by Bill Gates.
Robert Rohde, Lead Scientist for Berkeley Earth and the person who carried out most of the analysis, noted that "Sudden drops in the early temperature record (1753 to 1850) correspond to known volcanic events." Volcanoes spew particles into the air, which then reflect sunlight and cool the earth for a few years.
Of course the accompanying carbon dioxide in the eruptive material will then contribute to a quicker re-warming.