Total energy in the system is radiation received from the sun minus that emitted from the earth's surface back into space. Both of these things are pretty well

Total energy in the system is radiation received from the sun minus that emitted from the earth's surface back into space. Both of these things are pretty well understood and fairly simple to calculate. As for the ice age business, climate modeling from 40 years ago is an entirely separate thing compared with today's climate modeling. The advances we've made in model resolution and understanding the physics is quite compelling.