Cretaceous Thermal Maximum

The CTM is notable for its dramatic increase in global temperatures characterized by high carbon dioxide levels.

Rising carbon dioxide resulted in a significant increase in the greenhouse effect, leading to elevated global temperatures.

[5] From 250 to 150 Ma, Pangaea covered the Earth's surface, forming one super continent and one gargantuan ocean.

[7] Measurements of the ratio of stable oxygen isotopes in samples of calcite from foraminifera from sediment cores show gradual warming starting in the Albian period and leading to the interval of peak warmth in the Turonian[8] followed by a gradual cooling of surface temperatures to the end of the Maastrichitan age.

Late Cenomanian sea surface temperatures (SSTs) in the equatorial Atlantic Ocean were substantially warmer than today (~27-29 °C).

A graph depicting data from the Phanerozoic Geological era, showing oxygen isotopes from present to 500 Ma. The isotope levels show an correlating increase in global temperatures due to glaciation and glacial retreat.
Depiction of average planetary temperature of Earth over the past 500 million years. Note that the scale of 500-100 Ma is halved to fit on the graph, with the Cretaceous Thermal Maximum occurring at the peak just before 100 Ma.