A Harvard study released Tuesday analysed 40 years worth of documents from Exxon Mobil, concluding that the fossil fuel titan has, since 1979, internally acknowledged that carbon emissions are responsible for climate change, even as it has spent thousands over the years publicly denying the global consensus. As internal findings from peer-reviewed research grew more and more conclusive of human-instigated climate change, its public face insisted that climate change research was ambiguous.