How does the global temperature relate to El Nino temperature? Do we know without having El Nino data?
> there is global historical temperature data
Reconstructed from proxies. Not all experts in the field agree on how reliable the proxies actually are, especially over such long time periods.
This Wikipedia article has a graph of the last 2000 years: https://en.wikipedia.org/wiki/Global_surface_temperature
And yes, I am aware that earth has possibly been covered in ice/slush and also that the avg global temp has been 10C (or more) higher than it is now, but humans were not around for either scenario.