But his most significant legacy lay in advancing the science of cooling, where his contributions are immortalized in the name of the International System of Units temperature measurement, the kelvin. By formulating the thermodynamic laws that led to human control of cold — and thus to today’s refrigerated world — Kelvin inadvertently helped utterly transform what we eat, where it’s grown, and how healthy it is, both for us and for the planet.
This year marks the bicentenary of the birth of William Thomson, Lord Kelvin. You could be forgiven for having missed it — celebrations have been nonexistent — but in his day, Kelvin was revered. His seemingly endless accomplishments included laying the first transatlantic telegraph cable, inventing the dripless tap, and being the first person in the world whose house was illuminated entirely by electricity, as a result of which he was showered with so many honors that contemporaries claimed he was entitled to more letters after his name than anyone else in the British Commonwealth.
Today nearly three-quarters of everything Americans eat passes through a distributed perpetual winter of refrigerated warehouses, trucks, shipping containers, and chill cabinets. But as Kelvin’s second law of thermodynamics should have warned us, all the energy consumed to cool food is helping warm the planet to unsustainable levels. Generating the power to run cooling equipment, whether it be electricity for refrigerated warehouses or diesel fuel for “reefer” trucks, already accounts for more than 8 percent of global electricity usage. (Cold-storage companies are currently the third-highest industrial consumers of energy.) On top of that, many of the chemicals that are often used inside the vapor-compression refrigeration system that Kelvin’s discoveries made possible are also super-greenhouse gases: They cause hundreds — even thousands — of times more warming, on a per ton basis, than carbon dioxide.
What’s more, the hotter the planet gets, the more energy it takes to cool things. The standard vapor-compression cycle works by using refrigerant chemicals to absorb heat from inside a box — your home fridge or a warehouse — and then dump it into the external atmosphere. And the warmer it gets outside the box, the harder the refrigeration machinery has to work. For every degree Fahrenheit increase in ambient temperature, your fridge uses at least 2 percent more energy.
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To make matters worse, much of the world does not yet have a US-style cold chain but has begun to build one — and many of those places are also experiencing rapid population growth. The chemicals and energy used to refrigerate food already account for more than 2 percent of global emissions — the same as aviation. If everyone alive today were to have access to a cold chain similar to the one we rely on, these emissions would increase at least fivefold.
The energy-intensive