The End of the Era
By about 4,500 years ago, the climate began its slow deterioration to present day arid conditions. Humans no longer lived permanently at Gobero but rather migrated through the area with livestock, sometimes leaving a hearth or discarding their undecorated pottery.
there might have been a worldwide climate change 4500 years ago
more here about the climate change 4500 years ago that affected the Harappan civilization.