 |
|
|
|
|
|
|
|
|
|
|
|
| q |
Explanation 1: A result of the gradual
(tectonic-scale) cooling.
|
|
|
Tectonic-scale cooling
due to the decrease of CO2
|
|
|
è
cooling reach a threshold value 2.75 Myr ago
|
|
|
è moderate-size ice sheets can form in northern hemisphere ice during major
|
|
|
summer insolation minima and disappeared completely during summer
|
|
|
insolation maxima.
|
|
|
è
the falling CO2 levels continued
|
|
|
è
cooling reached another threshold value 0.9 Myr ago
|
|
|
è that ice sheets never completely disappeared during
weak summer insolation
|
|
maxima
|
|
|
è
ice sheets began to grow larger and persist longer
|
|