Bob Lee Swagger wrote:

"What was the climate like at 2000 ppm ?"


Reply:
It is thought that average Earth temperature was about 10 degrees
warmer towards the Poles, leveling out near the Equator, in other
words, the equator was not much warmer then today, most of the
increase being noticed in the higher latitudes.
The Mezozoic Era runs from about 250 million years ago up to
65 million years ago and includes the Triassic, Jurassic, and
Cretaceous Periods. A fascinating period of time on Earth if you like
dinosaurs like Tyrannosaurus Rex and Triceratops and Velociraptor etc.
It's thought that ice caps may still have existed, but much smaller
and seasonal then now. Rainfall would have generally been higher, due
to higher humidity, but there would still have been a few desert
areas as well.
Plant life was lush and thick, food for the pant eating
dinosaurs, Dinosaurs ruled the world, and the first mammals, that
would ultimitely lead to us, also appeared in the world at this time.
Somehow these little mammals survived whatever wiped out the
dinosaurs. (One or more meteorite impacts perhaps had something to do
with it. ( Chicxulub)).
It's believed that they lived in burrows under the ground. That may
have helped them.. I don't know.
It is believed that CO2 was many times higher then today... at 2000
ppmv, about 500 % higher then now, and oxygen was maybe 3 - 5 %
lower.

There are many sources of study on the subject of Paleoclimatology
on the Internet. The history of the Earth is really quite interesting.