Anthropogenic Climate Change-driven Atmospheric Angular Momentum Increases Length of Day

Increasing atmospheric angular momentum can alter the fundamental circulation cells that drive the Earth’s climate system and also slow the Earth’s rotation. Prominent examples include the expansion of the Hadley Cell and increasing Length of Day (LOD). Utilising the hundred ensemble member simulations of CESM2-LE with the SSP3-7.0 scenario, we reveal an equatorial super-rotation state of the earth with increased greenhouse gas emissions. With global warming, the momentum exchange between the solid earth and the atmosphere diminishes with reduced surface torques, suggesting slowing of the earth’s rotation. An accelerating atmosphere decelerates the earth’s rotational speed, bringing about challenges to precise time-keeping through increasing LOD. Our results demonstrate that climate-driven LOD changes due to atmospheric angular momentum variations can start as early as 2050, posing problems to global timekeeping. These findings illustrate that with continued warming along with astronomical tidal forcings and postglacial rebound processes, anthropogenic climate change will influence the earth’s rotational rate.