The Egg Was First, No, the Chicken, No Never Mind An evergreen in Eli’s business is which came first exiting the ice age, the temperature or the greenhouse gas concentrations. Since the forcing is orbital changes, it is reasonable to expect at least some initial lag in the greenhouse gas and that includes water vapor, but the length of this lag has been an issue ever since Monnin, et al’s analysis of the EPICA Dome C core inferred a lag of 800 + 200 years. This has become an evergreen amongst the less serious, and indeed, there has even been considerable discussion by reasonable folk . Jeff Severinghaus provided an answer So one should not claim that greenhouse gases are the major cause of the ice ages. No credible scientist has argued that position (even though Al Gore implied as much in his movie)