The Pliocene epoch is fairly recent in the Earth's lifetime, in the age of the mammals. According to:
Pliocene Role in Assessing Future Climate Impacts
"The middle part of the Pliocene epoch, approximately 3.3–3.0 million
years ago [was] about 2–3 C warmer globally on average than today". It
also states that "the mid-Pliocene was similar to today in terms of the
positions of the continents and oceans and atmospheric carbon dioxide
concentrations, but global warmth was distributed differently".
Although similar in many ways to today, the sea levels
were 25 metres higher and there was less ice sheets and glaciers. The
orbital movements were different, being dominated by obliquity rather
than eccentricity. This resulted in higher temperatures warming high
latitude oceans driving ice-albedo feedback. Maybe these changes had an
impact on the flora and fauna causing less carbon to be transported
from the atmosphere through the hydrosphere to be stored in the
lithosphere?
Pliocene Role in Assessing Future Climate Impacts "The middle part of the Pliocene epoch, approximately 3.3–3.0 million years ago [was] about 2–3 C warmer globally on average than today". It also states that "the mid-Pliocene was similar to today in terms of the positions of the continents and oceans and atmospheric carbon dioxide concentrations, but global warmth was distributed differently".
Although similar in many ways to today, the sea levels were 25 metres higher and there was less ice sheets and glaciers. The orbital movements were different, being dominated by obliquity rather than eccentricity. This resulted in higher temperatures warming high latitude oceans driving ice-albedo feedback. Maybe these changes had an impact on the flora and fauna causing less carbon to be transported from the atmosphere through the hydrosphere to be stored in the
lithosphere?