There was already strong evidence that a major wave of Indo-European expansion coincided with a major arid climate event in West Eurasia. The archeology in this study further confirms this conclusion.
Diagnostic features of a catastrophic aridization of climate, desertification, and paleoecological crisis in steppes of the Lower Volga region have been identified on the basis of data on the morphological, chemical, and microbiological properties of paleosols under archeological monuments (burial mounds) of the Middle Bronze Age. These processes resulted in a certain convergence of the soil cover with transformation of zonal chestnut (Kastanozems) paleosols and paleosolonetzes (Solonetz Humic) into specific chestnut-like eroded saline calcareous paleosols analogous to the modern brown desert-steppe soils (Calcisols Haplic) that predominated in this region 4300–3800 years ago. In the second millennium BC, humidization of the climate led to the divergence of the soil cover with secondary formation of the complexes of chestnut soils and solonetzes. This paleoecological crisis had a significant effect on the economy of the tribes in the Late Catacomb and Post-Catacomb time stipulating their higher mobility and transition to the nomadic cattle breeding.Demkina et al., "Paleoecological crisis in the steppes of the Lower Volga region in the Middle of the Bronze Age (III–II centuries BC)", 50(7) Eurasian Soil Science 791-804 (July, 2017).
As an aside, sadly, on of the authors passed away between the writing and the publication of this article.
A scholarly account of the effect of the same event on the Akkadian Empire in Mesopotamia from 1993 from the citations to this paper can be found here.