claim: Doubling the concentration of atmospheric CO2 from its pre-industrial level, in the absence of other forcings and feedbacks, would likely cause a warming of ~0.3°C to 1.1°C.
evidence: Further evidence for environmental change around the P–Tr boundary suggests an 8 °C (14 °F) rise in temperature, and an increase in CO 2 levels by 2000 ppm (for comparison, the concentration immediately before the industrial revolution was 280 ppm, and the amount today is about 410 ppm).
category: Permian–Triassic extinction event