It's possible there were higher spikes in the past, but I would guess that they were all pretty dramatic events, and yes the earth used to be much hotter in the past.

This is obvious if you think about it, all that carbon in the ground had to be in the air before photosynthetic life.

And before any life, the Earth was a molten ball of liquid rock.

https://en.wikipedia.org/wiki/Paleoclimatology