But first, in order to appreciate what aridization meant to the actual human beings that lived on the steppe of that time, I've linked a trailer to a series called "The Dust Bowl" by Ken Burns on PBS.
The dust bowl was an environmental catastrophe. Not as bad as this man-made disaster, though.
Chatter networks informed people of prospects in other places. Moving into Europe would have been a rather bold move, so I wouldn't call them hapless refugees. They needed land, Europe had land.
PALEOECOLOGY, SUBSISTENCE, AND 14C CHRONOLOGY OF THE EURASIAN
CASPIAN STEPPE BRONZE AGE
Shishlina, Zazovskaya, VanderPlicht, Hedges, Sevastyanov, Chickagova
RADIOCARBON, Vol 51, Nr 2, 2009, p 481–499 [Link]
ABSTRACT. Combined analysis of paleoenvironment, 13C, 15N, and 14C in bone, including paired dating of human bone and terrestrial materials (herbivore bone, wood, charcoal, and textile) has been performed on many samples excavated from Russian
kurgan graves. The data can be used for dietary reconstruction, and reservoir corrections for 14C dating of human bone. The latter is essential for an accurate construction of chronologies for the Eneolithic and Bronze Age cultures of the Caspian