From your articleDon't mock Nobel Prize winner Michael Mann.
The search for truth starts with understanding that if the Medieval Warm Period existed before the industrial revolution then the man-made global warming (MMGW) theory of CO2 forcing sudden warming in the 20th century is baseless because our recent warming is not unusual, unique, unnatural, nor greenhouse gas related.
Here we see the denier contention that because warming took place before the Industral Revolution, manmade CO2 cannot have caused the current warming. I was just told yesterday that no AGW deniers believed this.