Dave Roberts at Grist has a blast from the past - Exxon boasting how burning fossil fuels will melt glaciers (when they changed their mind about this remains unclear) - Oil: enough energy to melt glaciers! .
From a sharp-eyed reader comes this ad for Humble Oil (which later merged with Standard to become, yes, Exxon). It may win the All Time Millenial Award for Maximal Irony. It’s from a 1962 edition of Life Magazine, available on Google Books (click for larger version):