"M. Berkelhammer led an international team to a cave in Cherrapunji, Meghalaya, ‘among the wettest locations on Earth with an annual average precipitation in excess of 11,000 mm’, and studied the isotopic variations in a stalagmite: Oxygen 18 isotope as an index of precipitation, and the Uranium-Thorium method for absolute dating of the stalagmite, which went back almost 12,000 years for a growth of nearly 2 m. The results highlighted a ‘dramatic event ... ~ 4000 years ago when, over the course of approximately a decade, isotopic values abruptly rose above any seen during the early to mid-Holocene and remained at this anomalous state for almost two centuries.’ This suggested either ‘a shift toward an earlier Indian Summer Monsoon withdrawal or a general decline in the total amount of monsoon precipitation.’ The study’s ‘tight age constraints of the record show with a high degree of certainty that much of the documented deurbanization of the Indus Valley at 3.9 kyr B.P. occurred after multiple decades of a shift in the monsoon’s character....’"