Weakened and Irregular Miocene Climate Response to Orbital Forcing compared to the modern day

Abstract. Orbital forcing is a well-established driver of Pleistocene glacial-interglacial cycles, but its role in warmer climates remains less clear. Using climate model simulation, we assess temperature response to maximum and minimum boreal summer insolation during the Miocene and pre-industrial (PI) time. Both exhibit broadly anti-phased responses, but the Miocene shows weaker and less coherent patterns. Three notable differences emerge: (1) Boreal land regions respond less strongly in the Miocene due to dampened albedo feedbacks from altered vegetation; (2) Tropical Africa experiences stronger cooling under high insolation, driven by an intensified hydrological cycle with a broader Tethys Ocean under warm climate; (3) The Southern Ocean warms unexpectedly under low insolation, linked to sea ice involved albedo feedback. Lower internal temperature variability in the Miocene suggests enhanced climate stability and weaker orbital pacing. These findings highlight the importance of background climate state in shaping orbital-scale climate and interpreting proxy records.