SPEAKER_01: Amazing, fascinating stories of inventions, ideas and innovations. Yes, this is the podcast about the things that have helped to shape our lives. Podcasts from the BBC World Service are supported by advertising.
SPEAKER_02: 50 Things That Made the Modern Economy, with Tim Harford.
SPEAKER_00: Imagine we could control the weather at the push of a button, making it warmer or cooler, better or drier, the implications would be enormous. No more droughts or floods, no heat waves or icy roads, deserts would become verdant, crops would never fail. As it happens, climate change has sparked some crazy sounding ideas for hacking the climate, such as spraying sulphuric acid into the upper atmosphere or dumping quicklime in the oceans. Clever as humans are, however, we're nowhere near precision control of the weather, at least if we're talking about outside. But since the invention of air conditioning, we can control the weather inside. That's not quite as big a deal, but it still had some far reaching and unexpected effects. Ever since our ancestors mastered fire, humans have been able to get warmer when it's cold. Cooling down when it's hot has been more of a challenge. The eccentric teenage Roman emperor, Elagabulus, made an early attempt at air conditioning by sending slaves into the mountains to bring down snow and pile it in his garden, where breezes would carry the cooler air inside. Needless to say, this was not a scalable solution, at least not until the 19th century, when a Boston entrepreneur named Frederick Tudor amassed an unlikely fortune in a similar way. He carved blocks of ice from New England's frozen lakes in winter, insulated them in sawdust and shipped them to warmer climes for summer. The rest of the country became addicted. Until artificial ice-making took off, every mild New England winter caused a panic about ice famine. Air conditioning as we know it began in 1902, and it was nothing to do with human comfort. The Sackett and Wilhelms lithography and printing company in New York became frustrated with varying humidity levels when trying to print in color. Color printing requires the same paper to be printed four times in cyan ink, magenta, yellow and black. And if the humidity changed between print runs, the paper would slightly expand or contract. Even a millimeter's misalignment looks awful. The printers asked Buffalo Forge, a heating company, if they could devise a system to control humidity. Buffalo Forge assigned the problem to a young engineer, barely a year out of university. Willis Carrier was earning just $10 a week. That would be below minimum wage in today's money. But he figured out a solution. Circulating air over coils that were chilled by compressed ammonia maintained the humidity at a constant 55%. The printers were delighted, and Buffalo Forge was soon selling Willis Carrier's invention wherever humidity posed problems. From textiles to flour mills to the Gillette Corporation, excessive moisture rusted the razor blades. These early industrial clients didn't care much about making temperatures more comfortable for their workers. That was an incidental benefit of controlling the humidity. But Carrier saw the opportunity. By 1906, he was already talking up the potential for comfort applications in public buildings such as theaters. It was an astute choice of target market. Historically, theaters often shut down for summer. On a stifling hot day, nobody wanted to see a play, and it's not hard to imagine why. No windows, human bodies tightly packed, and before electricity, lighting provided by flares. New England ice was briefly popular. In the summer of 1880, New York's Madison Square Theater used four tons a day. An eight-foot fan blew air over the ice and threw ducts towards the audience. Willis Carrier called his system the weathermaker, and it was much more practical. The burgeoning movie theaters of the 1920s were where the general public first experienced air conditioning, and it quickly became as much of a selling point as the films. The enduring Hollywood tradition of the summer blockbuster traces directly back to Carrier. So does the rise of the shopping mall. But air conditioning has become more than a mere convenience. Computers fail if they get too hot or damp, so air conditioning enables the server farms that power the internet. Indeed, if factories couldn't control their air quality, we'd struggle to manufacture silicon chips at all. Air conditioning is a transformative technology. It's had a profound influence on where and how we live. Air conditioning has changed demographics too. Without it, it's hard to imagine the rise of cities like Dubai or Singapore. As residential units spread rapidly across America in the second half of the 20th century, population boomed in the Sunbelt, the warmer south of the country, from Florida to California. It rose from 28% of Americans to 40%. As retirees in particular moved from north to south, they also changed the region's political balance. The author Stephen Johnson has plausibly argued that air conditioning elected Ronald Reagan. Reagan came to power in 1980. Back then, America used more than half the world's air conditioning. Emerging economies have since caught up quickly. China will soon become the global leader. The proportion of air-conditioned homes in Chinese cities jumped from under a tenth to more than two-thirds in just 10 years. In countries like India, Brazil and Indonesia, the market for air conditioners is expanding at double-digit rates. And there's plenty more room for growth. From Manila to Kinshasa, 11 of the world's 30 largest cities are in the tropics. The boom in air conditioning is good news for many reasons, beyond the obvious that life in a hot summer is simply pleasanter with it than without. For example, studies show that air conditioning lowers mortality during heat waves. In prisons, heat makes inmates fractious. Air conditioning pays for itself by reducing fights. In exam halls, when the temperature exceeds the low 20s, students start to score lower in maths tests. In offices, air conditioning makes us more productive. According to one early study, it made US government typists do 24% more work. Economists have since confirmed that there's a relationship between productivity and keeping cool. According to Jeffrey Heale and Jisung Park, a hotter-than-average year is bad for productivity in hot countries, but good in cold ones. Crunching the numbers, they conclude that human productivity peaks at between 18 and 22 degrees. But there's an inconvenient truth. You can only make it cooler inside by making it warmer outside. Air conditioning units pump hot air out of buildings. A study in Phoenix, Arizona found that this increased the city's nighttime temperature by 2 degrees. Of course, that only makes air conditioning units work harder, making the outside hotter still. On underground metro systems, cooling the trains can lead to sweltering hot platforms. Then there's the electricity that powers air conditioning, often made by burning gas or coal, and the coolants air conditioners use, many of which are powerful greenhouse gases when they leak. You'd expect air conditioning technology to be getting cleaner and greener, and you'd be right. But demand is growing so quickly, even if the optimists are right about possible efficiency gains, there'll be an eight-fold increase in energy consumption by 2050. That's worrying news for climate change. When will we get inventions to control the outdoor weather too?
SPEAKER_02: Stephen Johnson offers delightful details of the history of keeping things cold in his book, How We Got to Now. For a full list of our sources, please see bbcworldservice.com slash 50 things. If you like what we've been doing on 50 things, please do rate or review us wherever
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