Marxists are sociopaths and sociopaths are Marxists. They're people who will say anything they think will get them power over others and pretend to be anything that will contribute to that goal. They are never sincere about anything.
It doesn't matter to them if there was ever any mainstream scientific support for globo-warmthink. There never was. They could care less. It's not about the climate, it's about power over their fellow man.