In the US, much of the population has migrated south, in part because of air conditioning, which makes the heat in the South and Southwest tolerable. Medicines that require room-temperature storage are usable there, unlike in poor countries with hot climates. Everywhere, heat waves can be deadly: In the US, they cause more deaths than most other weather calamities combined. In 2003, 70,000 people died during a heat wave in France.

Most power that runs AC today relies on fossil fuels, which ironically heat the planet. Future generations may condemn us for our failure to deal effectively with climate change, but people insulated against the weather can easily push the problem away. Office buildings often are overly air-conditioned for the convenience of men wearing suits. Raising the temperature would improve worker efficiency and save two dollars per worker, yet when people point this out, others consider them too sensitive. Despite the problems of air conditioning, however, Green feels “immensely grateful” for it and gives it three stars.

In 2007, Green got an eye infection from Staphylococcus Aureus—the dreaded Staph germ. These bacteria invade some people more than others. Before antibiotics and antiseptics, Staph infections were usually lethal and made surgeries into probable death sentences.