Awblain,
I'd love to know what the climate will be in 100 years but the simple truth is that our current knowledge/ technology is not up to that sort of prediction. Seeing how climate has changed in past and trying to work out why is part of the learning process to predict the future...and it's fascinating!
Ice ages commenced from just the sort of climate that we are currently experiencing. You've described the process of establishing an ice age but not the catalyst...we need to keep investigating the past to work out whether it could happen again. Remember that global warming is predicted to be of the order of a few degrees - I can't see that stopping the onset of an ice age.