I assume they rejected it, given the anti-malthusian nature of Marxism.
On paper the USSR had some of the strictest environmental laws in the world, however, in most cases they were just paper laws and were widely ignored. Ironically, the USSR did very detailed studies on environment contaminants such as mercury. In some cases the EPA actually used Soviet reports on mercury and other toxic chemicals as a data source because the Soviet studies were so detailed.
In general, the Soviet Union had a lackluster record on the environment. One typical example of this was the sulfur dioxide problem. Behind the iron curtain making monumental statues of Lenin, Stalin, etc, out of cheap materials was popular, so in many cases these statues were heavily affected by acid rain. The Soviet response was to hide the affected statues.
In 1988, the United States, USSR and Japan all voted against a UN proposal to hold carbon dioxide emissions at 1988 levels through the year 2000.
In 1989, at the Malta Summit, Bush brought up the upcoming formation of the IPCC and associated conference on "climate change" with Gorbachev. Environmental advocates hailed this as "progress". Generally speaking, the global warming initiative did not catch on until the 1990s when the Soviet Union had already collapsed.
Years later, Gorbachev became, like Gore, a strong proponent of global warming activism. However, there was no significant interest in the global warming topic during his tenure as the President of the Soviet Union.