The cause of global warming has been standard science since 1970's, Exxon included.

Democracy Now!: "A new report by InsideClimate News reveals how oil giant ExxonMobil’s own research confirmed the role of fossil fuels in global warming decades ago. By 1977, Exxon’s own senior experts had begun to warn the burning of fossil fuels could pose a threat to humanity. At first, Exxon launched an ambitious research program, outfitting a supertanker with instruments to study carbon dioxide in the air and ocean. But toward the end of the 1980s, Exxon changed course and shifted to the forefront of climate change denial. Since the 1990s, it has spent millions of dollars funding efforts to reject the science its own experts knew of decades ago."