page_title: Paleocene–Eocene Thermal Maximum
section_title: Weather
hierarchical_section_title: Paleocene–Eocene Thermal Maximum / Effects / Weather
caption_attribution_description: Species: Azolla caroliniana Family: Azollaceae Image No. 1
context_page_description: The Paleocene–Eocene Thermal Maximum, alternatively "Eocene thermal maximum 1", and formerly known as the "Initial Eocene" or "Late Paleocene Thermal Maximum", was a time period with a more than 5–8 °C global average temperature rise across the event. This climate event occurred at the time boundary of the Paleocene and Eocene geological epochs. The exact age and duration of the event is uncertain but it is estimated to have occurred around 55.5 million years ago.
  The associated period of massive carbon release into the atmosphere has been estimated to have lasted from 20,000 to 50,000 years. The entire warm period lasted for about 200,000 years. Global temperatures increased by 5–8 °C.
  The onset of the Paleocene–Eocene Thermal Maximum has been linked to volcanism and uplift associated with the North Atlantic Igneous Province, causing extreme changes in Earth's carbon cycle and a significant temperature rise. The period is marked by a prominent negative excursion in carbon stable isotope records from around the globe; more specifically, there was a large decrease in ¹³C/¹²C ratio of marine and terrestrial carbonates and organic carbon.
context_section_description: The climate would also have become much wetter, with the increase in evaporation rates peaking in the tropics. Deuterium isotopes reveal that much more of this moisture was transported polewards than normal. Warm weather would have predominated as far north as the Polar basin. Finds of fossils of Azolla floating ferns in polar regions indicate subtropic temperatures at the poles. The Messel pit biota, dated to the middle of the thermal maximum, indicate a tropical rainforest environment in South Germany. Unlike modern rainforests, its latitude would have made it seasonal combined with equatorial temperatures, a weather system and corresponding environment unmatched anywhere on Earth today.
caption: Azolla floating ferns, fossils of this genus indicate subtropical weather at the North Pole
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