J. Clim. http://dx.doi.org/10.1175/JCLI-D-11-00263.1 (2011)
The tropical atmospheric circulation system known as the Walker circulation is expected to slow under global warming, according to climate model simulations. An analysis of changes in a suite of meteorological variables over the past 60 years corroborates this suggestion.
Hiroki Tokinaga of the University of Hawaii at Manoa and colleagues compiled numerous independent data sets documenting weather conditions in the tropical Indo-Pacific region over the past six decades. They detected a number of changes, including a decline in marine cloudiness over the western tropical Pacific Ocean, a reduction in precipitation over Indonesia, a slowdown in the northeast trade winds and a convergence of surface winds over the central tropical Pacific. All of the changes are consistent with a weakening of the Walker circulation.
The researchers note, however, that the factors responsible for the slowdown are not yet clear.