Weakened miocene temperature response to orbital forcing compared to the modern-day

Abstract

Although orbital signal is widely identified in Miocene proxy records, the climate mechanisms linking insolation changes to regional temperature within this warm, low-ice period remains not well known. Here we use fully coupled climate model simulations to assess temperature response to maximum and minimum boreal summer insolation under Miocene and pre-industrial (PI) conditions. Under both conditions, temperature exhibits broadly anti-phased responses to increased and decreased insolation, but the Miocene response is overall weaker, with regionally dependent contrasts and reduced symmetry between two orbital cases. Three notable Miocene-PI differences emerge: (1) reduced boreal continental sensitivity in the Miocene due to dampened albedo, water-vapor and cloud feedbacks in a warmer, low-ice climate; (2) stronger Miocene cooling over tropical North Africa under high insolation, driven by intensified hydrological and moisture-feedbacks supported by a wider Tethys Sea; (3) reversed Southern Ocean anomalies under low insolation, where poleward-restricted Miocene sea ice enables winter insolation changes to trigger positive ice-albedo feedbacks. These results demonstrate that background climate state strongly modulates orbital-scale responses and provide important context for interpreting Miocene proxy records and long-term changes in Earth's climate sensitivity through the Neogene.