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Number two already has an answer. At the end Permian mass extinction, the Chicxulub meteor impacted the earth. This either caused or coincided with a massive lava flow in Siberia called The Siberian Traps. This burned up a whole lot of coal, increasing the CO2 to 50,000 ppm. The geologic record indicates the temperature rose between 10 and 15°C. The atmosphere today is not so different from that of 265 million years ago.

Human activity has caused CO2 to increase from 280 ppm to 400 ppm, an increase of 120 ppm. This indicates APGW is 0.036°C . . . if you believe the science.