If
one looks at the temperature charts of the past four glaciations and
interglacials of the Pleistocene, note that the rising rate of
temperature at the end of each ice age that leads into each interglacial
period is steep and continuous (due to Milankovitch cycle). The highest
temperature of each interglacial is at its onset. The peak at the onset
of our current interglacial, the Holocene, however, was not as high as
the previous interglacials' peak temperatures because a huge comet blast
12,900 years ago caused the Younger Dryas cooling period that lasted a
thousand years which tempered our current Holocene interglacial's peak
temperature.
Note: Our interglacial's "naturally" occurring
highest temperatures ended 5,000 years ago during which time gray whales
traversed the Northwest Passage between the Pacific Ocean and the
Atlantic). Today's warming trend is now once again allowing the gray
whales to access the polar route. Despite being hunted to extinction in
the Atlantic in the 18th century, they are now starting to appear in
places as unlikely as off the coast of Israel.
https://opentextbc.ca/geology/wp-content/uploads/sites/110/2015/07/Glacials-and-Interglacials-.png
http://wattsupwiththat.com/2015/07/27/younger-dryas-cooling-event-said-to-be-comet-related/
http://ottawa-rasc.ca/wiki/index.php?title=Odale_articles_extinctions
http://www.scientificpsychic.com/etc/timeline/asteroid-impact.html
http://www.indiana.edu/~geol105/images/gaia_chapter_4/milankovitch.htm