There's a logical fallacy in what you are suggesting.
Just because it has happened naturally before doesn't mean
- it's not man caused now, and
- it's not worth avoiding
The property damage and human impact costs of man made climate change clearly justifies the cost of changing our energy systems away from greenhouse gasses.
(And, we'll run out of fossil fuels eventually anyway, so developing the technology to replace them is going to be needed anyway.)
