The Anthropocene tasks literary critics and historians with rethinking literature through the lens of a civilizational catastrophe not yet fully realized but well-modeled and forecast in the IPCC reports, which describe a future planet drastically altered by greenhouse gas emissions. The hidden angle of literature is that it has always subtended a long arc from a mostly stable climate regime to the chaotic one that awaits above 400-plus ppm. Within literary texts we may find clues to explain how, in the face of a planetary emergency, we persist in our frustrating denialism (and find, too, perhaps some remedies for it). The American Renaissance is an important locus for such rereadings. This essay takes an indirect line through the central figures associated with the period (Emerson, Thoreau, Whitman, and Hawthorne), adding Dickinson, Poe, Fuller, and Susan Fenimore Cooper. The remarks on these authors’ “climate-imaginary” are mostly observational, sometimes notional, and admittedly provisional. Uncovering the climatic unconscious of the American Renaissance can only be understood as a literary version of paleoclimatology, with all the attendant gaps and uncertainties.