Bryson opens the chapter by talking about the Tambora mountain explosion of 1815. The explosion was equivalent to sixty thousand Hiroshima-sized bombs, and killed a hundred thousand people. This was proceeded by 1816,known as the year without a summer, where global temperatures were abnormally low. This caused mass famine due to crop failure. However, the global temperature that year only fell by 1.5 degrees Fahrenheit. But, as Bryson points out, Earth’s natural thermostat is “an exceedingly delicate instrument” (420).

Bryson goes on to say that the nineteenth century was a cold time: “For two hundred years Europe and North America in particular had experienced a Little Ice Age, as it has become known, which permitted all kinds of wintry events—frost fairs on the Thames, ice-skating races along Dutch canals—that are mostly impossible now” (420). For this reason, scientists during this time failed to see that compared to former epochs, their weather was balmy. In fact, they failed to understand how arctic reindeer bones were uncovered in warm climates and how vast rocks were stranded in improbable places.

While there was a theory that giant floods had carried the boulders onto mountainsides, it was James Hutton who theorized that widespread glaciation was the culprit.