In this essay I argue that Hemingway's much-discussed inner conflicts and self-contradictions on display in Green Hills of Africa (GHoA) are symptoms of his struggling with cognitive dissonance in view of his active contribution to the demise of the natural world he claimed to love. In this, Hemingway's predicament mirrors that of the humankind as a whole in the age of anthropogenic environmental change. Through exploration of selected passages from GHoA and of the way they exemplify specific cognitive biases that influence the way humans interpret and respond to global warming, biodiversity loss, and other environmental crises, I demonstrate the utility of cognitive ecocriticism for illuminating individual and social (in)action on these challenges.