Unlike the relatively mild interglacials
driven by the tilt, wobble and orbit of the Earth, the PETM fundamentally transformed the planet.
Humans could hardly be to blame if mammoths were able -- as in previous interglacials
-- to hole up in some chilly redoubt that was too remote for habitation or hunting.
During the interglacials
, the basin fills up with lakes.
The pollen in SU2, being overwhelmingly derived from trees, refers to their interglacial
origin, but not any typical forest succession or pollen-zonal record of known interglacials
was observed (Fig.
It appears that even during interglacials
the climate can oscillate between warm and cold, and yet the warm intervals are short-lived.
Until now, temperatures during the warm periods between ice ages - known as interglacials
- were thought to be only slightly warmer.
Earth did indeed plunge into an ice age about every 100,000 years, punctuated by warm spells, or interglacials
, that lasted about 10,000 years.
More recent interglacials
were only 10 000 to 20 000 years long and we're already 10 000 years into the current one.
The study says about 430,000 years ago, the glacial periods started to lengthen and interglacials
started to shorten.
However, the work of the brilliant Scotsman James Croll in the 1880s showed how orbital eccentricities had a marked effect on the amount of solar radiation received on earth, and could account for glacials and interglacials
However, the scenario of cold, dry glacials, and warm, wet interglacials
is rather too simplistic.
It occurred in the Hoxnian interglacial
and was about 250,000 years old; dating was typological or relative to pollen-based terrestrial sequences; two interglacials
separated three full-on glaciations, and well made ovates were a stage in a developmental trajectory.