The Indian monsoon variability and civilization changes in the Indian subcontinent

Although while describing the periods and their relation with data , they strictly rely on the so called AIT/AMT time frame , the data apparently suggest that during early and mature phases monsoon was strong with warm and wet climate (the phase had climatic stability) and the  intensification happened around  ~4550 YBP, but slowly started to decline though remained considerably strong up to   ~3850 YBP). So the 4.2 ka BP event did not create a sudden impact in ancient India , they reckon start of drier and cooler conditions around ~4100 YBP, but from ~3850 YBP to ~3300YBP , the dry and cool conditions prevailed which coincides with de-urbanization,reduced river flows and eastward migration  . But  the period of ~3400–3050 yr BP according to them, was when conditions improved before getting bad around ~3100 YBP , they reckon after that there was intensification of rain again and after were some more dry periods around 600-500 BC with more dry and wet periods followed. They have tried to link each dry and wet phase, with some significant periods of India's history and pre-history. I must tell this approach can be quite  risky and confusing , though is interesting and innovative nevertheless. 

The Indian monsoon variability and civilization changes in the Indian subcontinent

Gayatri Kathayat,1 Hai Cheng,1,2* Ashish Sinha,3 Liang Yi,4 Xianglei Li,1 Haiwei Zhang,1
Hangying Li,1 Youfeng Ning,1 R. Lawrence Edwards2

The vast Indo-Gangetic Plain in South Asia has been home to some of the world’s oldest civilizations, whose fortunes ebbed and flowed with time—plausibly driven in part by shifts in the spatiotemporal patterns of the Indian summer monsoon rainfall. We use speleothem oxygen isotope records from North India to reconstruct the monsoon’s variability on socially relevant time scales, allowing us to examine the history of civilization changes in the context of varying hydroclimatic conditions over the past 5700 years. Our data suggest that significant shifts in monsoon rainfall have occurred in concert with changes in the Northern Hemisphere temperatures and the discharges of the Himalayan rivers. The close temporal relationship between these large-scale hydroclimatic changes and the intervals marking the significant sociopolitical developments of the Indus Valley and Vedic civilizations suggests a plausible role of climate change in shaping the important chapters of the history of human civilization in the Indian subcontinent.

Yog .

See also :
Holocene landscape dynamics in the Ghaggar-Hakra palaeochannel region at the northern edge of the Thar Desert, northwest India