Somewhere between 7k-15k years ago there was a massive flood that changed the world. Every culture has stories of this flood in their mythology, e.g. Atlantis, and there is rich geological evidence for it.
What caused this flood?
Scientists theorize there was massive and rapid increase in temperature which quickly melted glaciers from an earlier ice age.
How did that happen? No one knows.
Why are there ice ages and why do they end?
No one knows.
Please do not tell your children their lives are meaningless unless we solve the intractable problem of climate change.
We can make the planet better in terms of clean air. water, and land, but changing weather patterns is orders of magnitude beyond us. We do not and likely never will have the technology to control the behavior of the massive nuclear furnace of the sun.