ESS101C
Prof. Jin-Yi Yu
One Reason: Higher CO
2
Level
q
CO
2
level was higher 100 Myr
ago.
q
Although higher atmospheric
CO
2
level can account for the
warm climate 100 Myr ago,
this mechanism alone can not
explain the extremely small
equator-to-pole temperature
gradient at
that time.
(from
Earth’s Climate: Past and Future
)