Kolbert explores the problem of climate change from several different angles. Most of these, such as the rerouting of ocean currents, melting glaciers, and overall global warming have the potential to destroy habitats and displace populations: “In 1979, the satellite data show, perennial sea ice is covered 1,700,000,000 acres, or an area nearly the size of the continental United States […] Since then the overall trend has been strongly downward” (26). Beginning with the population of Shishmaref, Alaska, Kolbert tours the habitats affected by climate change across the world. As permafrost at the poles begins to melt, she shows in Chapters 1 and 3, carbon dioxide and methane stores within it are released into the atmosphere. Global warming risks turning this into a self-perpetuating cycle.

In Chapter 4, Kolbert takes a different approach, tracking the migration of butterfly species, and observing the alterations to the hibernation habits of mosquitoes. Positioning the climate crisis within a well-known contextual framework, Kolbert references Charles Darwin’s theory of natural selection. She concludes that all biological species are under threat if natural ecosystems continue to be disrupted. Should her readers resist the idea of being subject to natural selection, Kolbert reminds them in Chapter 5 that human civilizations have been wiped out by climate change in the past.