Answer:
Greenhouse affect - atmosphere traps heat
Ice age - coldest phase of climate cycle
Sun's output - can vary
Greenhouse gases - atmosphere traps even more heat
Yes yes yes yes yes yes yes.
A possible cause was a meteorite hit the earth. it caused many organisms to become extinct because it blocked out the Sun so plants couldn't grow and herbivores couldn't eat the plants and carnivores couldn't eat herbivores.
