The Data
<a href="http://www.actuaries.ca/meetings/annual/1999/Hengeveld.pdf>; lots of it anyway
You've got to look at several different graphs and pay attention to dates to see the correlations though. It's not laid out at kindergarten level. Make that stable temperature for 1000 years from 900 to about 1860. I did not remember the length of time in the temperature graph correctly. That answers some of your questions because they predate that period. El-nino (which can now be predicted by computer models by the way) or other long term regional upsets may explain the other
Regards,
Mark