Anthropogenic warming-driven atmospheric circulation shifts and angular momentum increase: influence on the Earth’s rotation

Changes in the large-scale atmospheric circulation that regulate Earth’s climate can slow its rotation by increasing the Length of Day (LOD). Using large-ensemble simulations from three global climate models under the SSP3-7.0 scenario, we find that global warming-driven changes in Atmospheric Angular Momentum (AAM) propagate into measurable variations in LOD. These arise from modifications in both the mass and motion components of AAM. As the climate warms, expansion of the Hadley cell, intensification of subtropical jets, and weakening of tropical trade winds enhance the motion of the AAM, while a strengthened westward pressure gradient force associated with mountain torque and weakened surface friction torque indicate a reduced efficiency of momentum exchange with the solid Earth. Together, these processes accelerate the atmosphere and slow Earth’s rotation. By the late 21st century, AAM-driven LOD increases reach 10–18% of the lunar tidal friction trend, highlighting anthropogenic climate change’s role in Earth’s rotational dynamics.