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Every day, without conscious thought, you make dozens of decisions based on weather. What to wear, whether to carry an umbrella, whether to walk or drive. Emma opens by noting that most of us have remarkably little understanding of how weather actually works — then explains the whole system from one word: the sun.
Emma builds from first principles: the sun heats Earth's surface unevenly, equatorial regions getting more direct radiation than polar ones, and the atmosphere is constantly trying to redistribute that heat. The key mechanism is convection — warm air rises, cooler air rushes in to replace it. That beautifully simple process is responsible for wind, clouds, rain, and storms. All of it. She explains the water cycle (evaporation, condensation around dust particles, rain), pressure systems (high pressure brings clear skies because air is sinking; low pressure brings rain because air is rising), the Coriolis effect causing storms to spiral differently in each hemisphere, and cold and warm fronts. Then thunderstorms: inside a cumulonimbus cloud 15 kilometres tall, collisions between ice crystals and water droplets separate electric charge until the voltage difference produces a discharge — lightning. Thunder is the shockwave. Neev brings the cultural history: Zeus, Jupiter, Thor, Indra, Tlaloc — every ancient culture gave weather a face because it punished and rewarded and killed your crops, and you needed someone to negotiate with. Lewis tracks the health impacts he sees: seasonal affective disorder, heat deaths in elderly patients, and the clarification everyone always asks for — cold weather doesn't cause colds. Viruses do. We just spend more time indoors in winter.
Lewis ends on the climate change link: warmer oceans provide more fuel for cyclones, a warmer atmosphere holds roughly 7% more water vapour per degree of warming. So when it rains, it really rains. What used to be a one-in-a-hundred-year flood event is becoming one-in-twenty. The physics of weather hasn't changed — convection is still convection. We've just turned up the thermostat.
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