IPCC Fourth Assessment Report: Climate Change 2007
Climate Change 2007: Working Group I: The Physical Science Basis

3.7.5 Summary

Variability at multiple time scales strongly affects monsoon systems. Large interannual variability associated with ENSO dominates the Hadley and Walker Circulations, the ITCZ and monsoons. There is also good evidence for decadal changes associated with monsoonal rainfall changes in many monsoon systems, especially across the 1976–1977 climate shift, but data uncertainties compromise evidence for trends. Some monsoons, especially the East Asian monsoon system, have experienced a dipole change in precipitation with increases in one region and decreases in the other during the last 50 years.