You all know how miserably hot it’s been across America this last week. 100 degree temperatures everywhere. It’s been incapacitatingly hot. As I write, it’s 10pm and it’s still 93 degrees outside. I can hardly think. I’m currently sitting in nothing but my skivvies, chugging iced drinks, and stretched as close to the too-far-away window AC unit as this too-short keyboard tether will allow. Enjoy the image.
So I’ve been tuning into the weather reports more often than normal which is saying a lot for me. Because I regularly go out of my way to know the weather for the upcoming 5-10 days. I know it’s a little obsessive, but it gives my life a weird sense of security knowing what’s coming (or the gist of what’s coming). It’s been a habit for years — it probably developed shortly after the security of an afterlife disappeared and I needed a new forecast to fill the void. Or maybe it’s just a weird habit.
Anyway, the point is I’ve been watching a lot of weather. And I’ve been hearing the heat index thing tossed around more than ever before. It’s everywhere. The HEAT INDEX! It makes weather into super weather. It’s not just 102 degrees, but as our local weatherman Glen “Hurricane” Schwartz might say, “With the heat index that means it’s 125 degrees, people! Fuckin A! Death Valley shit! We’re all gonna die!”
So the heat index. It’s a scary thing. Today I went hunting for an explanation. I came across an interesting Canadian website that explains the history of the heat index (called the humidex in Canada where the system was first developed in the 1960s to “describe how hot, humid weather feels to the average person”). It’s a pretty thorough article written by a physicist. It describes not just the heat index but the wind chill scale as well. I won’t try to explain the math used behind the formulas, but I’ll fill you in on some of the interesting details.
We all know that the temperature feels colder when there is a wind and we all know that we feel more malaise when it's hot and there is high humidity. In 1939 explorers in Antarctica devised experiments to quantify that sensation of greater cold due to wind. They calculated how much faster a column of water froze when exposed to windy conditions than non-windy conditions. How clever. They devised some formulas, and voila, the wind chill was born. The formulas basically relate two variables: wind speed and temperature. Those experiments and formulas remained unchanged until 2000 when a US/Canadian committee convened to update the system and the variables. The kinks seem to have been straightened out.
The heat index came much later. It grew out of a paper published in 1979 by two Canadians called “A method of quantifying human discomfort due to excessive heat and humidity.” It was meant as a way of quantifying the risk posed to human beings at different levels of heat and humidity. It depends on three measurable variables: temperature, vapor pressure, and dew point. This scale has been used more and more widely in public weather reports in Canada and the US since the early 1990s. As of today, there has not yet been a revision of the formula.
Interestingly, the fashion of stating the temperature with the wind chill is not yet in wide use in Europe. Apparently European news reports of our North American weather do not always account for the wind chill factor when reporting our temperatures and, hence, have the effect of dramatically overstating our winter temperatures.
I could not find any information about whether the use of the heat index is fashionable yet in Europe. If it is not, I can only imagine that their news reports of our summer temperatures might also be overstated.
The best part of the website I mentioned above is its interesting indictment of the current system. He systematically reviews the deficiencies of the current extreme temperature indices. He starts by posing the problem on all thinking folks' minds: How can science quantify sensations? It’s an admirable enterprise, but inherently doomed.
There is a tendency in emergency rooms to have patients define their degree of pain (or anxiety or depression) on a scale of 1 to 10, with 10 being the worst pain they have ever experienced and 1 being no pain at all. During my ER rotations in med school and residency I was constantly amazed at how many times a patient described their pain as a 10–people who might be sipping a soda while we talked or watching a game show on TV over my shoulder. I eventually started to add qualifiers: “Let’s suppose a 10 is the pain you would experience if your arm was being slowly sawed off with a hacksaw.” I was further amazed at how many of those people would maintain their score of 10. The possibility of universalizing and usefully quantifying a person’s subjective experience of discomfort became a clear impossibility. There are too many variables in individual experience to standardize a quantifiable system of subjectivity.
In addition, the website goes on to describe the inadequacies of the current formulas for defining wind chill and heat index. There are mathematical parts of the formulas that have no clear origin or justification and thus the precision of the formulas themselves is debatable.
Finally, he states: “An index which is the function of two measurements does not give more information than two measurements themselves.” I find this argument intriguing, but perhaps not philosophically sound. I will leave the integrity of that assertion to the trained philosophers on this site.
In any case, it's hotter than fuck outside (and in) and I've got to put down this keyboard, but hopefully in the next day or two, amidst the chaos of the ambulance picking you up for your heat stroke, having read this post, you will pause for a moment and whisper to the EMT, “That heat index thing is bullshit.”
Fight the power, people. Truth matters.
brilliant post, farrell.
i was entertainted and educated, all at once.
i am looking forward to getting home and watching glenn hurricane schwartz at night with you.
love,
trixie
i’m trying to “enjoy the image”: are those the same boxer-brief-type skivvies that you draped around your neck while swimming in the ocean in Santa Monica?
i enjoyed this post, Farrell… especially since it’s been cool here in So Cal lately, enabling me to forget (at least until our heat index ramps up again) the fact that, on the hottest day in recent memory, i foolishly tried to buy an A/C unit at the local Home Depot and was laughed right out of the building…
Jeremy,
So you did try to buy an air conditioner.
Farrell,
Awesome post it speaks to that part of me that has to fight against the fear I feel whenever I read an article about the rise in shark attacks or random violence. Obviously the news media will do what ever they can to keep us buying papers or watch them dance around in front of giant weather maps. One of the most interesting surveys I’ve ever read or herd about consisted of two questions:
One: how many hours a week do you watch television?
Two: what do you think the odds are that you will be the victim of a violent crime within the next week?
The results were shockingly correlative; the more TV watched the greater the fear. But fuck man, the heat is a drag!
Scott
PS: It was so much fun to have you out here in the LBC. We hope to see you again real soon.
Hello Farrell,
I have a much-less-secret-after-this-comment obsession with weather.com. You know, you can get hour-by-hour or 10 day forecasts (my two favorites!)? You can type in your old zip code from when you lived in San Francisco and see if they’re getting rain. You can watch current satellite view– and you can naively believe it all…since, according to your post, it’s all sadly (but only slightly?) inaccurate.
I love and will miss my weather ignorance.
Come on back– out to Cali; the reprieve from the heat has been so pleasant and we can have late night patio drinks again.
Hey–
thank you trixie: i anxiously look forward to your return. as does william. you are missed–as you know.
jeremy: bless you for attempting to enjoy the image. alas, it was not the skivvies from santa monica night-swimming. those were a polyester/nylon blend. last night (and tonight) is all about cotton. also, i too, know the humiliation of the home depot laughter. as you’re aware i unsuccessfully tried a similar purchase a couple years ago. i now shop at lowes.
scott: i’ve never seen that study before. i love it. yes, that is near the same spectrum of media craziness where the heat index exists. god it was so much fun hanging with you and steph in the lbc. i have posters (you know whatimtalkinabout) to remind me that it was real. i hope it happens again soon.
lisa: i just explored weather.com. many thanks. it’s features are superior to weatherunderground.com and has now supplanted my favorite weather site. and oh how i wish i were on a patio in la tonight sipping free beers with friends. so nice to have met you and your entourage.
an update: funny timing, there was a piece on NPR tonight by melissa block about the heat index. alas, it was disappointingly uncritical.
i heard the npr piece! broadcast PST @ 6:27 pm and i thought of you fondly. dude, you are on the pulse. the piece was uncritical, yes, but i loved the title of the “seminal paper” by RG Steadman which inspired it: An Assessment of Sultriness. sexy.
“An index which is the function of two measurements does not give more information than two measurements themselves.”
Well, depends on what you mean by “information.” What if I told you that David Wright of the Mets has had 404 at-bats this season and gotten 125 hits? Well, you could do some quick division in your head, but you’d probably be happier if I just told you he’s batting .309 on the season. Another baseball stat that’s just a simple function of a few variables, the slugging average, is slightly more complicated and tells you quite a bit. Nothing you wouldn’t know by being told the variables and the formula (SLG = (s + 2d + 3t + 4hr)/ AB), but you’d still probably rather just be told that Wright’s slugging average is .550.
In the case of the heat index, I take it that the formula that relates temperature, vapor pressure, and dew point is non-linear and gerrymandered to approximate how it feels to us at certain values of those variables. So yes, if you’re told the value of the variables and the formula, you’re technically not getting any new information by being told the heat index value. But the formula in this case has some information about human physiology and perception built in to it, so being told the three variables but not the formula isn’t enough. And in any case, who wants to do all that math?
but of course. exactly the kind of lesson that i (we) had hoped for. thank you dave.
I am a huge fan of the heat index and the wind chill factor, which justify my extreme sensitivity to any temperature outside of the 60-75 degree range. The psychological satisfaction if gives is plenty of scientific evidence for me. (Incidentally, my first knowledge of the wind chill factor was provoked by that Boomtown Rats song “Wind Chill Factor (Minus Zero),” which made it sound suitably dramatic.)
I constantly battle to communicate with my friends and family in england the dramatic nature of weather here and am thwarted in the first place by trying to quickly convert fahrenheit to celsius, and secondly by their lack of understanding of these indices. My mother is particularly annoying as she lives mostly in spain, where it may well be hot, but they have lovely dry heat with sea breezes. And then she puts the thermometer in the sun and says things like “it was 50 degrees celsius in the sun” and i say yes, but that’s meaningless, it’s 95 degrees here, but it’s a heat index of 110 and that’s really bad.
So, this is one bit of American science and culture that could helpfully be championed across the world.
“An index which is the function of two measurements does not give more information than two measurements themselves.”
Dave’s example, the batting average, gives more information than its components because it is a “statistic”. Statistics are meant to do just that—boil down pieces of information into meaningful measures.
The Humidex, on the other hand, is bullshit. In the 70’s the press invented the Misery Index, which was the simple sum of the inflation rate and the unemployment rate. Cute, but bullshit.
Bacon, what is the Humidex if not a statistic? How do you draw the line between meaningful numbers and useless ones? By defining “statistic” as “a figure that boils down pieces of information into meaningful measures”? Doesn’t that just become circular — making “statistic” into an honorific we apply to measures we like?
I agree the “misery index” was bullshit, but it sounds like it was about on the same level of computational difficulty as the batting average. Why is one bullshit and the other not? If Stella uses the heat index to convince her family she’s suffering, isn’t she using it in the same way a baseball scout uses the batting average to convince a team to make a trade?
“Doesn’t that just become circular — making “statistic” into an honorific we apply to measures we like?”
Yes exactly.
The Humidex attempts to be a statistic, but statistics is the science of tabulating so as to present “significant information” about a given subject. You be the judge where to draw the line.
Personally, I admire the Humidex’s attempt. At least it aims to be grounded in theory, thereby allowing us better to understand and interpret. Like the batting average. Not like the Misery Index.
But bacon, you seem to be ruling out the Humidex without saying anything other than “it’s not a statistic.” Why not? If they’ve done some experiments on how people respond to various combinatinos of heat and humidity, maybe the Humidex is a statistic with some explanatory force. In your view, how does it fall short in the attempt?
It falls short for all the reasons Ferrel mentioned. if you insist on calling it a statistic, I’ll let you.
I finally read that grouchy Canadian website that Farrell cited. His “reasons against these indices” are bullshit. Go down the line — they show a narrowly dogmatic misunderstanding of what science is. And those “problems with the math” are bullshit, too. Of course the formula is a little screwy — it’s gerrymandered to approximate human perception of temperature, which is not as simple as simply averaging a few terms. He seems to be objecting to the use of constants in the formula, but there ain’t nothing wrong with using constants.
Also, he misspells things like mad. “Reproductible.” “Sensationnalism” (more than once — not a typo).
I myself think the heat index is useful, more or less. It’s not as precise as some other measures, but it does a good job of telling you, quickly, how miserable it’s going to be outside. Stella thinks it’s useful, too. I don’t see any reason not to honor it by calling it a statistic.
if stella likes it, then let it be.
people people. it’s getting hot in here. now before dave and bacon start saying stuff like “why don’t you walk your statistic to the parking lot with me, bitch” i’d like to return to the post-enlightenment spirit of the post which was that the heat index–like other human inventions of measurement–is a relatively recent creation and is subject to all those same post-modern problems and critiques. Does it contain useful information for some? yes. Does it sensationalize misery? yes. Do French Canadians misspell things in English and sound funny when they talk? of course. I hope that we can soon move on to discussing more important things: Like figuring out the logistics of moving down to Scott’s future caribbean commune/death resort. that sounds quite delighful.
It was weird to keep coming back to the site and seeing how much conversation this post was generating. I’m not really that into the weather so I was ignoring the chain. Now, having sort of made my way through the tedium of Bacon and Dave’s exchange to Farrell’s put down of French Canadians, I chuckle.
Tedium? It’s the great battle between pragmatism and hoary scientism! What could be more exciting?