Wind chill, and its pointlessness

Slate has this very interesting little essay about the "wind chill factor." For those not in the U.S. (or not living in the cold parts of the U.S.), you may not know about our obsession with this number.

Typically, the weather report says the temperature is 25F but it "feels like" 10F (32 Fahrenheit is 0 Celsius). The "feels like" is temperature adjusted by the so-called "wind chill factor." It conveys the idea that keeping temperature constant, it feels colder when there is wind.

The Slate article covers a bunch of general issues related with inventing metrics:

• People love large numbers, in this case, because we are measuring cold temperatures, they like really small numbers
• The name of the metric may have little or nothing to do with what is being measured
• In seeking to make numbers more palatable to the public, people may choose less precise language that sometimes completely loses the original meaning. For example, "feels like" does not indicate that wind is at issue. Other factors like humidity also affect how cold one feels, at constant temperature.
• That said, the public is hungry for statistical concepts or metrics that can be explained easily and understood instinctively. There is nothing wrong with this desire.
• After a metric is established, it's not easy to dislodge it. Changing the metric renders the entire history useless. I also made this point in the chapter on obesity metrics in Numbersense (link).
• How cold one feels is affected by a system of multiple factors, including temperature, wind, humidity, etc.
• Any definition of the perceived temperature involves the notion of statistical adjustments

For more, read the Slate essay.

 

 

Comments

[James P Hansen]

Perhaps it may be pointless, misleading, whatever. At the core, I think it succeeds as good communication if it makes the average person think twice and take a heavier coat.

It truly is about effective heat loss, subsequent frostbite, and then hypothermia from inadequate insulation.

I mean the Slate author went to relatively great lengths to understand the history of windchill, why it is kinda bunk at best, and then decree its garbage and should go away. All without proposing a meaningful replacement folks could use in their day to day life to know how to prepare. Proposing that folks could use experience and observation to determine outside safety is nuts.

I suggest Slates authors and editors read the MPR weather blog and sometime. The meteorologists there go to great lengths to not only report the weather, but talk about weather reporting, its challenges in communicating to a semi-educated public, foibles (such as windchill) and so on.

When someone comes up with an interesting, reliable, related, and viable alternative for warning the general public about dangerously cold conditions, I'm more than happy to read about that. All else is navel gazing.

Dollars to donuts, I bet windchill warnings saved a lot of folks' literal backsides the last few days, failure of a statistic and all.

[Kaiser]

JH: You certainly have a good point about the ultimate goal. I'd rather it be called something else because it isn't just the wind.

[Antonio Rinaldi]

It's curious. Also here in Italy we speak about "temperatura percepita" (perceived temperature) but during summer when people suffer muggines and want to hear that the hot is hotter. :)
Anyway, I did some googling about perceived temperature and the moust hilaurious thing is its ridicolous unit of measurement.