Are you always cold? Always asking to turn the heat up? It can be the middle of summer, and I will still be cold in my sleeping bag, no matter how many blankets I pile on or how warm the night is. And let’s not even talk about the time I thought it was a good idea to try winter camping; I’m still getting over that decision in therapy. And then there’s my husband, who seems to have his own personal internal furnace, of which I am desperately jealous. He can be covered in snow with ice crystals dangling from his beard, and still claim to be completely cozy. So how is it that people can have such different perceptions of the same conditions?
It turns out that the science of how our bodies perceive winter and cold is a complex and evolving field. In the 1920s, the American Society for Heating and Ventilation Engineers developed the Effective Temperature index. This was the first attempt to summarize different environmental conditions as a standard temperature, but its use in winter was limited because its lowest operable temperature was 30°F. Then in the 1930s, the fun really started with scientists carefully monitoring energy and moisture exchanges for naked test subjects sitting on copper chairs in a carefully controlled chamber. The result of this slightly odd experiment was to determine an optimal average skin temperature for comfort of 91.4°F, along with standardizing units for thermal activity and resistance to cold by clothing.
Finally, the term we all know and love today, wind chill, was defined during the third Byrd expedition to Antarctica in 1939-1940. Scientists Paul Stiple and Charles Passel filled plastic cylinders with water to determine the rate of heat loss for different combinations of exposure to temperature and wind. Recording the time required for the water to freeze, they related this to the freezing of human flesh. Using a series of complicated equations for cooling rates, they created a table to estimate wind chill equivalent temperatures based on temperature and wind speed. These are the temperatures reported as “wind chill” by today’s meteorologists, and although some scientists contend that there are other relevant factors not included in this calculation, this is the measurement most rely on to get a true impression of what the weather will feel like.
The results of these experiments have been used by the Army to estimate the amount of clothing necessary for soldiers in various weather conditions, and are still used today to calculate comfort ratings by outdoor equipment companies. But ultimately, all of these calculations derive from averages, and most of us aren’t average. For example, maybe you heard about the study released this past summer that talked about the difference in temperature preferences for men and women in the workplace. It turns out that the average office temperature setting, usually around 70°F, was determined in the 1960s and is based on the metabolic rate of a 40-year-old man weighing about 154 pounds. Women, who now make up about half of the work force, are smaller, have less muscle mass (and more fat, unfortunately), and aren’t as hairy as men. These factors contribute to a slower metabolic rate and a faster cooling rate, which means that women generally produce about 35% less heat than a male under the same conditions, resulting in a preferred temperature of around 75°F. Clearly there’s a conflict here.
The business of keeping warm is a big one, especially this time of year, when avid outdoorsmen and women try to maintain high activity levels and adrenalin rushes throughout the cold winter. Companies compete to create warmer, breathable, more lightweight gear to better protect you from the wind and cold. And somewhere, in a back room in a dimly lit lab, there are college students sitting naked in copper chairs, working diligently to improve how we calculate wind chill and measure cold, all for the good of science, skiers, and people like me, who prefer a cozy blanket and hot cocoa with my copper chair.
Jaymee Squires is the Director of Graduate Programs at Walking Mountains Science Center in Avon. She loves to get out in the winter, but only after carefully calculating the appropriate layering for the weather.
