I remember a BBC documentary from when I was a child in the 1980's predicting an ice age.

They looked at ice cores, realised than an ice age happened every 100,000 years, and then correlated it with the wobble of the earth's axis. As the axis tilts away from the sun, it gets colder. We're already past the half-way point as the axis swings away from the sun. The only thing that's delayed the cold has been massive deforestation.