Lordy, people…
Predicting dry/wet winters is difficult. Atmospheric dynamics on day-month scales is chaotic.
Energy conservation on decade scales is easy. Knowing where warming will occur is difficult, but on average - it's getting warmer.
What happened 1000 years ago isn't of too much relevance. It's the 100 years in front of us that matters.
The condition for a starting an ice age is probably simple - winter snow stays through the summer in the high-latitude northern hemisphere. Off to on in a few seasons. Not so likely with current temperatures.