Climate change question - how much has the climate actually changed?

I can’t seem to find a solid answer anywhere. I find all sorts of graphs and stats about the USA and how much carbon emissions they are producing compared to the rest of the world, but how much has the climate changed as a whole? How much warmer is the Earth? How much higher are the sea levels? How much rain? Etc etc.

Also, why is this bad? Any resources for learning more about this? Thanks.