The response to orbital perturbations in an atmospheric model coupled to a slab ocean

Three experiments are compared. One has perihelion at summer solstice and a large obliquity; another has perihelion at winter solstice and a low obliquity. The first of these is favorable for warm summers; the second for cool summers. A third experiment, with perihelion at summer solstice and the lower value of obliquity, is used to examine the relative importance of the changes in perihelion and obliquity. The eccentricity is set at 0.04 in all cases. Surface temperature responses are as large as 15°C, with the largest response over North America in summer. Changes in monsoons and Arctic sea ice are consistent with previous GCM studies. -from Authors