Professor Dr. Jan Esper's group at the Institute of Geography at JGU used tree-ring density measurements from sub-fossil pine trees originating from Finnish Lapland to produce a reconstruction reaching back to 138 BC. In so doing, the researchers have been able for the first time to precisely demonstrate that the long-term trend over the past two millennia has been towards climatic cooling.
If you custom cherry-pick the endpoints for your graphs you can 'prove' just about anything. If the theory is that man has created a climate warming effect by the industrial revolution (pollution and accelerated use of natural resources) what sense does it make to go back to 138 BC to disprove the theory?
I'd have to look at the data. For example if this is the data, it would indeed show a long term trend over 2 millennia towards cooling
Year........Average temperature
BC 138.....65 degrees
BC 38.......64.8
AD 38.......64.6
AD138.......64.5
AD500.......64.2
AD750.......64.1
AD1000.....63.9
AD1250.....63.8
AD1500.....63.6
AD1750.....63.5
AD1850.....63.8
AD1900.....64.0
AD1950.....64.3
AD2000.....64.6
Long term there is a cooling trend. But from the industrial revolution forward there is a warming trend.