Could you cite the source for that graphic? I'd love to use it but know that's the first thing I'll be asked
The data was pulled from the Vostok Ice Core samples provided by N.O.A.A. The addition of the comment about human activity was mine. It is pretty hard to really spot where human activity began, relative to the scale, but if you imagine "When humans began burning fossil fuels", it would be a very small line on the right end of the scale.
One should note; CO2 is higher than ever before. But that should be taken in the context that CO2 is a lagging factor (it follows temperature, does not drive it) and the periodicity of our global temperatures are not human made.