Well coming off the KT Impact, the Earth cooled a little bit, but not much.
Went back up and hit another high at the end of the Paleogene, and
then the Earth started a dramatic history of cooling, which we are still a part of.
And you can see, then, the rapid drop in temperature as we move into the Eocene.
Now, the Eocene is marked by another fundamentally critical event in Earth's
history, and that was the rise and the development of the Antarctic ice sheet.
So from the age of the dinosaurs in the Cretaceous through the Eocene,
it was a planet without ice sheets, and
then the Earth cooled again to the point where ice could be developed on the poles.
So the Antarctic,
the onset of Antarctic glaciation in the Eocene, nicely shown on this diagram.
And from that Eocene time period, then we've seen an Earth where the relative
rates of some of the warming or cooling have increased, but
not nearly as rapidly as what we're seeing in the modern day Earth.
Over the last 100 years the average rise in
Earth temperature has been about 1 degree Celsius.
But from about 2000 up until 2100, the estimates are that the rise in
Earth's temperature could be as great as 8 degrees Celsius over 100 years.
And 8 degrees Celcius is dramatically steeper and faster than any of
the types of temperature rises or drops that we see on these diagrams.
Was we go from the Eocene now were into a glacially dominated earth.
We have rises and falls, rises and falls, with an overall drop in temperature,
especially after we reach the end of the Oligacene and into the Miocene.
And so those drops continue until we get into the age of the ice, or
the Ice Ages in the Pleistocene.
So on the lower right-hand part of this diagram, you'll see we move into
the glacial episodes with high frequency, in a relative sense, change in
temperature, but nothing even close to what we're recording in modern-day Earth.
So this is the template we need to remember,
an incredibly warmer Earth at the age of the dinosaurs.
The KT Impact opening up ecosystem space, both in the terrestrial and
marine environments, and then a slow trend toward cooling,
then the onset of the Antarctic glacial sheets.
And then moving fully into the age of the ice.