Selected quotes:   

• <  "In 627, the heat was so great in France and Germany, says the London Standard, that all springs dried up; water became so scarce that many people died of thirst.
• <  "In 879, work in the field had to be given up; agricultural laborers persisting in their work were struck down in a few minutes, so powerful was the sun."
• <  " In 1000, rivers ran dry under the protracted heat, the fish were left dry in heaps and putrefied in a few hours."
• <  " In 1132, not only did the rivers dry up, but the ground cracked and became baked."
• <  "The Rhine River in Alsace nearly dried up." 
• <  "During the battle of Bela, in 1200, there were more victims made by the sun than by weapons; men fell down sunstruck" 
• <   "In 1303 and 1304, the Rhine, Loire and Seine Rivers ran dry...."

Quotes from the eras having thermometers: 

• <  "In 1718 it did not rain once from the month of April to the month of October. The crops were burnt up . . .The thermometer marked 36 degrees Reaumur (113 of Fahrenheit).
• <  " In 1753 the thermometer rose to one hundred and eighteen degrees."
• <  "In Paris in 1846, the thermometer marked one hundred and twenty-five degrees in the
• sun." 

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Thus it seems the Earth has been having cycles of very hot weather for quite a long time.  And these pre-dated the industrial revolution and also the electric power industry, by several centuries..  As skeptical scientists have often reported, CO2 is not the magic dial for temperature rises.  But natural Earth cycles seem more likely the temp driving force.