I agree that there was a bit of a tongue in cheek tone to the piece. For example, the title referenced the cold war. That being said, given the larger context of The Guardian's opinion pieces and their tendency towards feminist demagoguery, I read it as "I'm kidding!" (but I'm kind of serious, too.) There was also a mention of the higher temperature being better for the environment, which reinforced the "I'm only half joking" subtext for me.