This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Atmospheric circulation governs weather and climate, but it also carries angular momentum. When winds shift or mass redistributes, the atmosphere can exchange momentum with the solid Earth, slightly altering the planet's rotation rate.
This is not a new concept, but what happens under long-term global warming? Previous studies have projected an increase in atmospheric angular momentum (AAM). However, the reason remained unclear.
Was it simply stronger winds? Or was there a deeper dynamical restructuring of the atmosphere? We set out to answer this in our paper in npj Climate and Atmospheric Science.
Using large-ensemble climate simulations from three different global models, we examined how atmospheric circulation evolves under a high-emissions scenario. What emerged was a consistent and physically coherent picture: These are well-known responses to warming, but together they systematically increase AAM. At the same time, something equally important happens at the surface: momentum exchange between the atmosphere and the solid Earth weakens.
This reduces Earth's efficiency at "keeping up" with the changing atmosphere. A slightly faster-moving atmosphere and a slightly slower-rotating Earth. The changes we identify are subtle.
By the end of the 21st century, the increase in the length of day (LOD) due to atmospheric changes reaches about 10%–18% of the long-term tidal friction trend. At first glance, this may seem modest. But it is significant for two reasons: To place this in context, tidal friction has long been considered the dominant driver of long-term rotational slowing.
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