claim: But we do have other reliable indicators of temperatures before the late 1800s, and the evidence shows temperatures have been warmer than today for most of the past several thousand years, including warmer-than-present temperatures for most of the human civilization time period
evidence: Before the Industrial Revolution, naturally occurring amounts of greenhouse gases caused the air near the surface to be warmer by about 33 °C ( 59 °F ) than it would be in their absence.