After eight months of investigation, InsideClimate News presents this history of Exxon's engagement with the emerging science of climate change. The story spans four decades, and is based on primary sources including internal company files never before seen, interviews with former company employees, and other evidence. It describes how Exxon conducted cutting-edge climate research decades ago and then pivoted to work at the forefront of climate denial, manufacturing doubt about the scientific consensus that its own scientists had confirmed.