Polar forests of the Cretaceous

Cretaceous polar forests were temperate forests that grew at polar latitudes towards the end of the Mesozoic Era, known as the Cretaceous Period (145–66 Ma). At this time, global average temperature was about 10 °C (18 °F) higher and carbon dioxide (CO2) levels were around 1000 parts per million (ppm), 2.5 times the current concentration in Earth's atmosphere. High atmospheric carbon dioxide is one of the main causes of a pronounced greenhouse Earth in the Cretaceous, with a low global temperature gradient. This means that high latitudes in both hemispheres were much warmer than they are now, and the Earth lacked ice caps.

High temperatures strengthened Earth's water cycle by moisture evaporation from the ocean surface. Absolute sea levels were much higher than they are today. Continental encroachment of seawater formed widespread shallow seas with some epeiric seas.

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