Coupled climate models may be used to simulate the consequences of changes in greenhouse gas emissions, and a number of such scenarios have been made for models participating in the Coupled Model Intercomparison Project. Using these simulations we have estimated expected changes in atmospheric angular momentum (AAM), a parameter that depends upon both redistributions in atmospheric mass distribution and changes in wind circulation.

For the axial component of angular momentum, we examine variations and trends in zonal AAM by latitude band and height from several models. Particularly strong increases in zonal winds can occur in the upper troposphere/lower stratosphere subtropics in both northern and southern hemispheres, strengthening the zonal jets there. This increase tends to occur more in the “high economic growth” scenario of the climate models than other scenarios. This change has occurred both over the 20th century according to models and reanalyses, and is forecast to occur over the 21st century as well, according to the simulations.

Changes in the axial component of the angular momentum of the atmosphere are reflected in its changes in other terrestrial components, and have been clearly noted in small but measurable changes in the rotation rate of the solid Earth below. Additionally, changes are noted in the equatorial components of angular momentum, especially for mass redistribution terms, which can be related to small motions of the Earth's pole. Thus overall reference frames for the Earth can be impacted by future changes in the atmosphere itself.