In the light of these results, They propose that global monsoon can be regarded as a system consisting of two main integrated components, one primarily driven by the oscillations of Inter-Tropical Convergence Zone (ITCZ) in response to the low-latitude summer insolation changes, anti-phase between the two hemispheres (i.e. the ITCZ monsoon component); and another modulated by the glacial-interglacial cycles, mostly synchronous at the global scale (i.e. the glacial-interglacial monsoon component). Although atmospheric CH₄ record integrates all wetland processes, including significant non-monsoonal contributions, it is the only and probably the best proxy available to reflect the past changes of global monsoon. However, the utility of CH₄ as a proxy of monsoon changes at any specific location is compromised by its bi-hemispheric nature.

Fig.1 The relation of the amount of sunlight at low-latitude in the northern and southern hemispheres and CH₄ of the second group. (Image by GUO)

Fig.2 The change of millennium-scale atmospheric CH₄ concentration. (Image by GUO)

Guo, Z.T., Zhou, X. and Wu, H.B., Glacial-interglacial water cycle, global monsoon and atmospheric methane changes. Climate Dynamics. DOI: 10.1007/s00382-011-1147-5 (See More>> )