The USSR totally knew about climate change being a thing. Climate change is not a "new thing". Oil companies have known about it for almost a century now, they built their oil rigs to withstand rising sea levels for example.

The USSR did know about it as well, at least since the sixties: https://www.gla.ac.uk/media/Media_329370_smxx.pdf

Fedorov’s article appears to be one of the earliest direct engagements with the problems associated with climate change and, more specifically, anthropogenic climate change in the Soviet Union. However, this theme received more concerted discussion and debate from the early 1960s. Two meetings of particular note took place in Leningrad in April 1961 and June 1962, both of which were organised by the Main Geophysical Observatory in tandem with the Institute of Applied Geophysics and the Institute of Geography and brought together a range of Soviet scientists, including geographers, in order to discuss the ‘problem of the transformation of the climate’ (see Gal’tsov, 1961; Gal’tsov and Cheplygina, 1962).