what was the global average temperature of the earth before industrialisation

According to the search results, the average global temperature before industrialization is not clearly defined. However, the pre-industrial era is generally considered to be from 1880-1900. The average global temperature has increased by a little more than 1° Celsius (2° Fahrenheit) since that time. It is also noted that the Earths climate can vary substantially even without human interference, due to factors such as the Sun's energy output and volcanic eruptions. Additionally, during the coldest part of the last glacial period, the average global temperature was about 11°F colder than it is today, while at the peak of the last interglacial period, the average global temperature was at most 2°F warmer than it is today.