Flannery was one of Exxon's top climate modelers after he joined the company in 1980. His research initially confirmed the findings of independent scientists, who said a doubling of CO2 in the atmosphere would raise average global temperatures by roughly 3 degrees Celsius. By 1990, however, Flannery served as Exxon's top scientific spokesman as it worked to derail international efforts to cut greenhouse gases from fossil fuel use. In 1998, he transitioned into a managerial role at ExxonMobil Corporation. Flannery spent three decades at the company; during that time, he served as a lead author of the Intergovernmental Panel on Climate Change's Working Group 3 (from 1998-2004) and was a member of multiple climate-related business committees. He continues to participate in the climate discussion as a fellow at Resources for the Future, an economic research and analysis nonprofit in Washington, D.C.