What you are describing are cycles. I have tried explaining people this but some people can NOT grasp the concept that their lives are just a spec of a timeline compared to a longer period such as global warming or global cooling. I have long used this explanation even before someone tried to show that global warming or global cooling is happening to the earth.
We are NOT in any threat of global cooling or global warming. It is a normal earth cycle that spans over several centuries.
However this concept of changing should not be used to excuse our responsibility to the earth --- our living planet.