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Wet-bulb temperature

137 points| vincent_s | 2 years ago |en.wikipedia.org | reply

176 comments

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[+] gorbypark|2 years ago|reply
I worked as a snowmaker at ski resorts for most my my adult life before getting into tech. We always use wet bulb temperatures because it’s a representation of temperature and humidity. With extremely low humidity, you can actually make manmade snow at about +3 degrees Celsius. That was always fun but scary, because a small change in humidity can turn snowguns into water guns in the blink of an eye.
[+] sokoloff|2 years ago|reply
I’ve occasionally wanted to try snowmaking at home on brutally cold days.

Any tips for someone wanting to try this at home? Let’s assume that I have access to tap water at 60psi dynamic pressure and air at 90psi and 10 SCFM continuous (more for short bursts if needed).

[+] samcheng|2 years ago|reply
If you haven’t read it yet, the first section of Ministry for the Future by Kim Stanley Robinson describes a wet-bulb event in striking detail. The horror of this climate-change catastrophe is what finally triggers a significant global cultural shift around climate change.

The passage was vivid enough for me to suggest preparatory measures to my retired parents. I wholeheartedly recommend the book to anyone interested in near-term climate impact!

[+] skyfaller|2 years ago|reply
I hate speaking negatively about Ministry for the Future, because I admire KSR, and we need fiction that confronts the climate crisis and shows people taking positive action to change the world for the better. Still, I sadly cannot recommend this book. To quote from my spoileriffic review,

"This does not help us imagine realistic positive outcomes to the climate crisis. Robinson correctly diagnoses the threats we face and immerses the reader in a very plausible near future. Unfortunately, any happy ending feels unearned as the world is essentially saved through magic, as humans/society respond in vanishingly unlikely ways."

https://bookwyrm.social/user/skyfaller/review/381179/s/compe...

[+] IKantRead|2 years ago|reply
> wet-bulb event

It's probably already too late, but I keep seeing people confusing the concept of "web bulb temperature" (all temperatures have a wet bulb temperature, even ones very pleasant for people) with "the human survivable maximum wet bulb". I frequently see people saying things like "when we reach wet bulb temps..", which feels a bit silly.

This always feels like talking about a "Kelvin event" or "Kelvin temps" referring a temperature reaching absolute zero.

[+] alangibson|2 years ago|reply
I stopped reading it because the premise is entirely unbelievable. A mass casualty event of pretty much any size would not lead us to do anything about climate change.

For evidence, look at the deaths in the USA from gives and cars every year. Yet there is zero momentum toward doing anything about those from a policy standpoint.

[+] dogman144|2 years ago|reply
I clicked into this to see if MFTF was mentioned. Powerful opening scene.

Other commenters criticizing the book for the ending and the positivity turn it takes are missing the point of why the book is valuable, I think.

Like for you maybe, it was the first book that got me serious about climate. The value isn’t in the ending, but in the first half with unpleasantly accurate the early “oh sh*t” disasters were and same for the totally inept societal responses.

Made me realize we were likely procrastinating our way into an emergency, and any magical way out we find IRL will be at a high cost of suffering. We will probably get disasters, we will get climate terrorism, and it will get much worse before we get saved (by magic blockchain carbon fediverse haha?).

[+] MH15|2 years ago|reply
First chapter of Ministry for the Future- incredibly powerful and harrowing.

Every following chapter- terrible, not worth your time.

[+] prepend|2 years ago|reply
I found that passage pretty disturbing too. But my takeaway was that there aren’t any individual plans you can make unless you plan on hanging out in a body of water breathing through a straw for a few days.

What prep did you recommend to your parents? I’m interested for what I can reuse or adapt.

[+] gonzo41|2 years ago|reply
In the book that event happens to India. I sadly think that when climate change starts killing people in poor countries (like it already is). The western wealthy world will ignore it for as long as possible.

I sometimes get very dark about the future we're headed into.

[+] bradford|2 years ago|reply
Maybe this is a pet peeve of mine, but I'm annoyed with the use of the term 'wet bulb event' here and elsewhere. Wouldn't it put less burden on the reader to just say "wet bulb 35C"? (That is the temperature that most people seem to be referring to when they say 'wet bulb event'.)

Every place on earth has a wet bulb temperature, all of the time. Saying "wet-bulb event" doesn't really help explain the web-bulb temperature's significance, which is buried in the wiki page:

"It has been thought that a sustained wet-bulb temperature exceeding 35 °C (95 °F)—given the body's requirement to maintain a core temperature of about 37°C—is likely to be fatal even to fit and healthy people, unclothed in the shade next to a fan;"

[+] JeremyNT|2 years ago|reply
I feel like the terms in use around this are quite abstract and hard to reason about. I like that the wikipedia article converts this to something more useful to intuit for most of us:

> Even heat-adapted people cannot carry out normal outdoor activities past a wet-bulb temperature of 32 °C (90 °F), equivalent to a heat index of 55 °C (131 °F). A reading of 35 °C (95 °F) – equivalent to a heat index of 71 °C (160 °F) – is considered the theoretical human survivability limit for up to six hours of exposure.

The US NWS, for example, uses heat index commonly. In the US south I seldom see it go much over 110F, and six hours is a long time to be exposed to the elements even at the current levels of heat.

This isn't just a case of hitting some threshold where we all drop dead, but as temperatures rise it will slowly cause people to migrate to more temperate climates and/or seek out better cooling structures (either actively through air conditioning or passively where that isn't an option).

[+] dahwolf|2 years ago|reply
I personally believe that I've been in a short-lived "wet bulb" situation twice in my life. In both cases, in the Amazon, pretty much at the equator, at some of the hottest days of the year. 40-45C, humidity near a 100.

A cold shower does nothing, it actually makes it worse as it activates your body to warm up. Stripping naked does nothing. Sweat just streams down the entire body as if a tap is open. It's near impossible to keep up with drinking water.

It was short-lived as the weather was extremely variable, but the feeling of being completely unable to cool down despite throwing everything and the kitchen sink at it, is memorable.

[+] rexer|2 years ago|reply
Surely a cold shower helps? If it causes your body to trigger self-heating process, surely that’s proof your body has been cooled to less than dangerously high levels and the shower has provided at least temporary relief.
[+] carapace|2 years ago|reply
I recently spent some time camping in a place that hit daytime temperatures of over 100°F. When it's that hot all you can do is wet your clothing and spray mist and fan yourself to get evaporative cooling. Thinking about wet-bulb temperature in that context was terrifying.

The hot dry breeze can cool you off. The hot humid breeze is death.

If you live somewhere where this could happen you should move now.

[+] drbig|2 years ago|reply
Temperature without humidity is like voltage without current, or per-capita GDP without the Gini coefficient. Many measures alone are of little practical value.

Stay _comfortable_ there!

[+] studmuffin650|2 years ago|reply
in my opinion, a lot of folks won't take climate change seriously until it adversely affects their way of life in such a dramatic way that they cannot deny it any longer.

A wet bulb event, occuring over multiple hours, would be that signal. Piles of dead bodies from folks who either were misinformed or weren't able to move to safety would be quite the wake up call.

[+] thworp|2 years ago|reply
In my experience the issue is not about taking it seriously, I've rarely met someone totally unconcerned in real life. The real issue is what to do about it, how to do it and in what timeframe.

With these wet bulb events and the breathless death counts in the media people get the impression that heat waves are bigger killers than cold winters, when it's the opposite (and if you include indirect and long-term deaths by an order of magnitude).

There are also some serious and well connected organizations advancing plans that I can only see as attempted mass murder. If your plan projects no cargo ships by 2035 you will kill millions from the fragility of food supply chains alone.

If you want to reduce fertilizer use, fine. Better targeting and smarter application can reduce the consumption by at least 30%. But if you want to use no fertilizer you will kill billions.

Even the more grounded and non-murderous proposals have some serious question marks. Electrify almost all energy use by running 300% overproduction of renewables, to be stored in batteries and pump storage that isn't even planned yet while at the same time increasing electricity demand by 400%? Yea sure that will get done in 30 years, no problem.

The climate doomers always insist that the extinction event will be caused by climate change destroying food supply. But crops can be bred, new areas can be cultivated and ressource use reduced. The fact that 6 billion of us only exists thanks to chemical fertilizer, mechanized agriculture and amazing seed variants is not open to argument though.

[+] hkpack|2 years ago|reply
> in my opinion, a lot of folks won't take climate change seriously until it adversely affects their way of life in such a dramatic way that they cannot deny it any longer.

It won't. People you are talking about have access to air conditioning. They will not care about people dying in distant places, whom become an annoyance after a while. They will just wish people die silently without complaining.

[+] whycome|2 years ago|reply
The 1896 New York heat wave lasted 10 days and killed ~1500 people. And has just 2 short paragraphs in Wikipedia (https://en.wikipedia.org/wiki/1896_Eastern_North_America_hea...)

> "This was 10 days [with temperatures reaching] 90 degrees at street level and 90 percent humidity, with temperatures not even dropping at night,"

https://www.npr.org/2010/08/11/129127924/the-heat-wave-of-18...

It wasn't necessarily a wake-up call then. But it may have at least been the crisis that spurred one guy...

[+] jncfhnb|2 years ago|reply
Some people have fantasies about these heatwaves that just decimate all living things. It’s not that simple.

It’s not THAT hard to cool down even if you’re incapable of sweating to do so. People aren’t idiots either. Despite imaginations of cultural hubris, people can tell when it’s deathly, disgustingly hot, and do not casually tank it until they die. And even if they did, they’re not idiots. If one person collapses, they’re not going to ignore them and continue to assume the heat is negligible. You don’t have to realize the nuances of your circumstances and the probability of death to understand that you are intolerably uncomfortable.

Yes of course heat waves are bad and can kill people. But wet bulb events are not a magic threshold that completely change the game.

[+] losvedir|2 years ago|reply
People will need to start thinking of the summer months in some places like the winter months in others: during certain periods you need shelter with working HVAC systems, and when you go outside you need suitable gear and emergency arrangements.

I live in the Chicago area, and in the winter working from my heated home and traveling between heated places in my heated car, it's sometimes possible to forget how uninhabitable it is outside! But you need to carry emergency jackets and other things in the car in case it breaks down and you lose your climate control. And I remember how scary it was when my furnace broke during a winter cold snap!

[+] nonethewiser|2 years ago|reply
But think about the solution. It's making A/C very accessible and reliable. That requires cheap energy with a high-uptime grid. There are many ways to solve this problem but adding difficult to meet constraints to energy companies that risk price and availability is not one of them.
[+] mrjaeger|2 years ago|reply
That's actually the inciting incident for the cli-fi book "The Ministry for the Future". Overall I really enjoyed the book, was a good mix of interesting economic/policy ideas interwoven through a compelling character based narrative.
[+] hiatus|2 years ago|reply
What exactly is a "wet bulb event"?
[+] HumblyTossed|2 years ago|reply
I don't even think that would change people's minds. They'll just call it fake news and blame it on someone's laptop.
[+] RcouF1uZ4gsC|2 years ago|reply
Sounds like we will be needing lots of reliable carbon-free energy, excellent electricity infrastructure, and lots and lots of air conditioning.
[+] weinzierl|2 years ago|reply
I find it interesting that in the US the weather report seems include the related dew point but in Europe it usually isn't.