The threshold is wet bulb 35 for 7 hours. That is when fit young humans can't survive. Older people die well before that of course.
And no, it doesn't happen regularly. I wasn't aware it had happened at all, although others here say it has. But it has come close. From https://www.telegraph.co.uk/global-health/climate-and-people... :
> Jacobabad crossed the 35C wet bulb threshold in July 1987, then again in June 2005, June 2010 and July 2012. Each time the boundary may have been breached for only a few hours, but a three-day average maximum temperature has been recorded hovering around 34C in June 2010, June 2001 and July 2012.
These people don't have the escapes you mentioned. They are in a city with no running water and no cars, let alone car parks. There is no river, but there are a couple of small lakes.
https://www.wunderground.com/blog/weatherhistorian/record-de...
The most dangerous / frequent occurrences seem to be measured in the middle east near shallow gulf coasts. Appleton Wisconsin holds the continental US record, apparently?
This is from 2011.
This looks more updated: https://www.weather.gov/jetstream/hi
and says:
> The highest dew points, and therefore the highest heat indices are usually found near warm bodies of water.
> In the world, the warmest water is found in the Persian Gulf where the water temperature typically reaches up to 90°F (32°C) in summer. Therefore dew points will be that high as well.
> The highest dew point ever recorded, 95°F (35°C), was recorded at Dhahran, Saudi Arabia, on July 8, 2003. With an air temperature of 108°F (42°C) the heat index was 178°F (81°C).
> In the United States, the highest dew point ever recorded, 90°F (32°C), was recorded at the New Orleans Naval Air Station, on July 30, 1987, Melbourne, Florida on July 12, 1987. Heat indices were in the 130's°F (50's°C).
> Appleton, Wisconsin also had a 90°F (32°C) dew point on July 13, 1995 with a heat index of 149°F (65°C)."
So, it happened once, in Saudi Arabia?
Jeez what a hot place... Any idea what geographic features make it so dang hot? It's not too far from water (just looking at a map).
Sibi is in a hollow formed by some mountain ranges to the north. Perhaps hot winds from the south get trapped there. Not sure about Jacobabad though…could never find any reason why it was so hot.
Another time I was in a car with no AC right after a rainstorm, and it was so hot in the backseat that every time the car stopped the heat became unbearable. When the car was moving we had some wind and it helped.
In Canada I’ve always noticed the temperature can be 5-10 degrees cooler under trees in a forest. Not sure if it’ll be so cool with high humidity but certainly trees will block the sun and trap air cooled by the ground, so they are the best defence against global warming.
It means some people simply have no means to escape such heat and will likely die.
In the US, they sometimes open cooling centers during heat waves so homeless people and poor people have a place to go. I never went to such but they did that in Fresno and bus rides were free if you said you were going to a cooling center.
And there may often be only one tap per 100 people in densely populated slums.
These events are usually short (for TW >35, majority only last an hour, see Sup fig 2), which is perhaps why we are not seeing many deaths associated with them.
With regards to immersing oneself in water, a bathtub is good so long as groundwater is available; if everyone starts filling their tubs for every heat wave it might start becoming more scarce. I would have thought natural bodies of water like the sea would have been a good choice, but the authors point out that in one region where wet bulb temps >35 were happening they also observed frequent sea surface temps >35 too (sup fig 16).
There are ways to survive and you have provided good ones, but they won’t be available to all who experience these events if they continue to increase in number. And excellent point about wildlife! That’s a whole additional side of it that will probably get lost in the mitigation effort…
And there are psychological issues that people just don't know what to do till it's too late. I was living an apartment with only 1 southern window, the heat was hard to vent. Once during a heatwave I found myself in a weird lethargy then I started going sick and then I found out the thermometer shows 40°C inside. I went outside immediately. Were not a healthy young man, that could have ended up badly. Since that I never underestimate the heat.
That does not mean 100% fatality rate is possible but it definitely might be more than 0.1%.
This is something that has puzzled me every time I park in the underground garage under City Hall in Palo Alto. It is always so hot down there compared to the outside air.
I was about to ask if anyone knows why that is, and then realized I could search for the answer:
https://www.google.com/search?q=why+do+underground+garages+g...
Lots of interesting opinions there, including a previous HN thread.
One discussion I liked showed up when I'm signed into Google but was missing from an incognito search:
https://philip.greenspun.com/blog/2013/07/05/stupid-geophysi...
There's also all the body heat, and the resistive braking of the trains which is being phased out.
If this starts to happen semi-regularly, you can bet my garden will turn into a little hobbit hill/cellar.
That said, I agree that if it happens suddenly to that extend, we would likely be looking at more than 0.1%.
People don't have trashcans, storage bins, etc?
"And seems you probably never bathed in 35°C water, it's definitely not refreshing."
Where is this 35C water coming from?
Also, if it's a humid heat, there are likely to be natural or artificial bodies of water around. Hopefully the people have been taking care of them and they aren't a cesspool.
Sure, some people may die, but it should be very low.
Edit: why downvote? All the excuses the previous person gave seem petty to me, so I'm wondering how that person came to their conclusion. Especially for where that hot water is coming from.
I’m inclined to say that this is not very survivable, regardless of your precautions, if your air conditioning has died.
A wet bulb of 35C means that there is a thermometer covered with a wet cloth reading that temperature. That could be 35C with 100% humidity, or it could be a higher temperature with a lower humidity.
Can you explain how your air conditioner keeps you cool? Do you think this machine is the only thing that can perform a similar function? It's all about removing excess heat from your body. An air conditioner does this by cooling air and removing humidity. This can be from the cool air on your skin and the ability for your sweat to evaporate. When your sweat can't evaporate you need another way to transfer heat. Water is very efficient for this due to its specific heat (anything at a cooler temperature with sufficient thermal mass can work). Some people can even become hypothermic in 27C water if left in it long enough.
Edit: I guess people just downvote things they don't like or find to be inconvenient.
How is that fully accurate? It seems to me that "not very survivable" is not accurate and is an over exaggeration. I don't expect a 50% death rate, even 10% would be extremely generous. It would be like me saying linux desktops are very common.
I would not leave my house. My house has insulation and thermal mass, which would delay the tempature from reaching that level until later. I could use water to cool myself, whether in the bath tub or a trashcan. I could use a fan if there's power (depends on the temperature and humidity to reach that wet bulb). I could use frozen objects (even without power, the freezer will stay cold for at least a day). I also have a generator to power these things if there's a short to medium term outage.
Their statement was not about changing one's circumstance. It was that even with precautions, it's not very survivable. This is neither accurate nor precise. It is very survivable with precautions.
I was specifically questioning things like where is the hot water coming from, people without tubs can't figure out how to save water, etc. Those claims sound overly pessimistic and simplistic to me.
Still, that factoid is troubling. These are conditions that exceed humans' operating conditions. We're used to that on the cold side. Plenty of people thrive (miserably) in places that get cold.
But, there are actually far fewer good cooling options. Air conditioning is more complicated than heating. You can heat with fire, warm clothes. Even exercise, though this is not sustainable. A sauna is nice, but people don't live in their saunas until temperatures get tolerable.
Also, the heat cutoff is more of a universal. A lot of organisms seem to start failing at temperatures like this.
That would definitely change cultures and economies, but if you can't get out of those places, it might be your only option.
"There is a clear connection between heat and drowning. That's when people want to go in or near the water, and the risks of drowning increase," FSL's Executive Director Kristiina Heinonen told Yle in July:
https://yle.fi/uutiset/osasto/news/drowning_deaths_reach_10-...
Sounds to me like a mostly not seen before thing
> Is there a name
"False analogy" is what comes to my mind, maybe there's something better
I guess it depends on where you are, I live on the Mediterranean, where, if you panic in the water, you're just standing in calm water. I imagine the ocean is much scarier.
> maybe there's something better
I think we do need something better, I see it too often for it to not have an exact name.
Yes, in my case I was imagining a wide river close to a many millions people city, and people from the slums (no AC) go there to cool down, and more and more people arrive all the time to the river, pushing those already there outwards, deeper water, people cannot swim
At rock concerts 10 000 people can create dangerous pressure, I wonder if a deadly heat wave and the chance to cool down at a specific place can do that too
Or maybe people would spread out along the water, but at the same time, it might be hard for an individual person with occluded vision to know what makes sense to do
Sometimes people rush out from a building in panic, everyone gets stuck in the door opening
A higher frequency of extreme cold in winter in areas that are not accustomed to it, like what recently happened in Texas, may also occur with similar consequences.
I don't think climate change will be a catastrophe movie directed by JJ Abrams. I think it will be a gradual process in which we pay back the "loan" of fossil fuel use with interest.
We put our civilization on a credit card without knowing the interest rate.
We could have really slowed down our running up the balance in the 1970s and 1980s with nuclear power, but we didn't. We could still be doing that plus deploying a lot of renewable and storage tech that was not mature back then, but we're doing far too little of that. We are still adding to the card balance and we still don't know the interest or the repayment terms.
If there are feedback loops in the climate system that we trigger, the loan could be an ARM with unscheduled interest rate increases and balloon payments.
Our children get to inherit most of this bill.
The municipalities in the relevant places ought to advice people to prepare well in advance (and how)
People can jump into fountains, or other bodies of water, hide at home, airconned buildings.
In the end, people can try to brave it, and wait for the relatively cool evening.
I don't know what exactly environment reaching 35C/95F web bulb means, but considering 1) it indicates temperature of a thermometer cooled by evaporation, and 2) body temperature of a human is ~40C/100F, I think it means evaporative cooling aka sweating is becoming useless. It won't be a huge stretch to consider that unsurvivable.
One issue that people who haven't experienced extreme heat might not realize is a lot of people just pass out really quickly. While it takes a while to go past the point of no return and they theoretically could be egressed to somewhere they can cool off and recover, if they're alone, they're not going to.
This assumes there are no alternatives to evaporative cooling via sweat.
My legitimate comments get downvoted and crap like this does not...
That's an exaggeration. Extreme heat (including heat waves that exceed this threshold) happen semi-regularly, and the death rate when they occur is nowhere near 100%. More like 0.1% or less.
Electrically-powered air conditioning is not the only way to cool a human body.
Simply escaping to an underground or substantially enclosed area is sufficient for periods of up to a few days, or even weeks depending on the thickness of the walls. Car parks, cellars, caves, etc... all retain a relatively constant temperature irrespective of temporary swings of the air temperature outside.
Similarly, immersing oneself in a body of water below about 36 C is also sufficient, and that's typically available even if the local air temperature and humidity exceeds safe levels. E.g.: Rivers "carry" the cold down from mountains, and are safe havens during temperature extremes. Even the local pool is sufficient, because water has such a massive thermal capacity that it won't heat up anywhere near as fast as the air around it.
At times like this you see people filling up their bathtubs and just hanging out in there until things blow over.
More worrying is what happens to wildlife. Some animals simply can't escape like humans and most animals can. For example in Australia a recent heatwave killed something like half of all flying foxes!