The global expression of millennial-scale climatic change during the glacial period and the persistence of this signal in Holocene records point to atmospheric teleconnections as the mechanism propagating rapid climate variations. We suggest rearrangements in the tropical convection system globally affected the concentration and location of atmospheric water vapour and modulated terrestrial and marine emissions of CH4 and N2O, providing a tropical mechanism of amplifying and perpetuating millennial-scale climate changes. A multi-proxy reconstruction reflecting various aspects of the intensity of the Arabian Sea Summer Monsoon shows strong millennial-scale variability over the past 90 kyr in which low intensity is associated with a southern shift of the Intertropical Convergence Zone (ITCZ) and an eastward shift in the equatorial convergence zone. The monsoon reconstruction, which is based on new data from a Somali margin sediment core, is supported by previously reported tropical paleoclimatic records and suggests that global scale millennial climatic variability is in part driven by modulations in the tropical hydrological cycle and tropical emissions of the greenhouse gases CH4 and N2O.