Shanghai to Near Very Dangerous 35 Degree Celsius Wet Bulb Temperatures This Week

[GliderGuider]

Ocean Heat Dome Steams Coastal China: Shanghai to Near Very Dangerous 35 Degree Celsius Wet Bulb Temperatures This Week

An ocean heat dome that formed over a broad area of the Pacific Ocean, the South and East China seas, and a large stretch of coastal China during late July continues to create a dangerous combination of record hot temperatures and high humidity.

According to reports from AccuWeather, the sweltering coastal China town of Shanghai hit a new all-time record high temperature of 105.8 degrees Fahrenheit (41 degrees C) on Tuesday. But this marker may just be a milepost to what is predicted to be a 107-108 degree scorcher on Wednesday and Friday. With humidity predicted to be around 50% and barometric pressure readings expected to hit 1005 millibars, these represent extraordinarily dangerous conditions.

Recent climate papers by former NASA scientist James Hansen have issued warnings of the potential for wet bulb temperatures on the surface of the Earth to start to exceed levels that are lethal for humans at 35 degrees C for longer and longer periods as humans continue to warm the atmosphere. Hansen notes:

One implication is that if we should “succeed” in digging up and burning all fossil fuels, some parts of the planet would become literally uninhabitable, with some time in the year having wet bulb temperature exceeding 35°C. At such temperatures, for reasons of physiology and physics, humans cannot survive, because even under ideal conditions of rest and ventilation, it is physically impossible for the environment to carry away the 100 W of metabolic heat that a human body gene rates when it is at rest.

[phantom power]

1. At some point, it stops just being the young/sick/elderly

I guess we are nearing that point.

[kestrel91316]

2. 108F is quite nasty, but we've had 119F right here in my corner of Los Angeles,

and THAT was dangerous.

35C is only 95F. That's what I consider the lower end of nasty. You just stay in the shade and don't exert a lot. Nobody dies from it.

[GliderGuider]

3. Remember, that's 35 "wet bulb" degrees. Not the same as plain old dry-bulb temperature.

http://en.wikipedia.org/wiki/Wet-bulb_temperature

The wet-bulb temperature is the temperature a parcel of air would have if it were cooled to saturation (100% relative humidity) by the evaporation of water into it, with the latent heat being supplied by the parcel.Wet-bulb temperature is largely determined by both actual air temperature (dry-bulb temperature) and humidity, the amount of moisture in the air.

Cooling of the human body through perspiration is inhibited as the wet-bulb temperature (and absolute humidity) of the surrounding air increases in summer. Other mechanisms may be at work in winter if there is validity to the notion of a "humid" or "damp cold."

Living organisms can only survive within a certain temperature range. When the ambient temperature is excessive, humans and many animals cool themselves below ambient by evaporative cooling of sweat (or other aqueous liquid; saliva in dogs, for example); this helps to prevent potentially fatal hyperthermia due to heat stress. The effectiveness of evaporative cooling depends upon humidity; wet-bulb temperature, or more complex calculated quantities such as Wet Bulb Globe Temperature (WBGT) which also takes account of solar radiation, give a useful indication of the degree of heat stress, and are used by several agencies as the basis for heat stress prevention guidelines.

A sustained wet-bulb temperature exceeding 35 °C is likely to be fatal even to fit and healthy people, unclothed in the shade next to a fan; at this temperature we switch from cooling the skin (losing heat to the environment), to warming it. As of 2010 wet-bulb temperatures only very rarely exceeded 30 °C anywhere.

At a wet-bulb tempetature of 35C the body loses the ability to cool itself by evaporation through sweating. That's extremely dangerous.

[kestrel91316]

4. I have 8 years of college in scientific fields and have never heard of this

"wet bulb" and "dry bulb" nonsense. Thermometers read what the temperature is. THAT is what temperature I am referring to.

I know what "heat index" is, but that isn't the term being used.

[Nihil]

6. You would have heard of it if you'd had to measure humidity.

> I have 8 years of college in scientific fields and have never heard of this
> "wet bulb" and "dry bulb" nonsense.

Guess that being in California means that you don't get much in the way
of moisture?




> I know what "heat index" is, but that isn't the term being used.

"Heat index" is an inaccurate simplification to try to get the information across
to people who don't understand the effects of temperature and humidity on their
body. That's why it was adopted by the US National Weather Service.

A more correct way to do it is to quote the wet bulb temperature (as the OP article did)
and to point out the danger point (as the Wiki extract did):

A sustained wet-bulb temperature exceeding 35 °C is likely to be fatal even to fit
and healthy people, unclothed in the shade next to a fan;

(My italics)

HTH!

[kestrel91316]

7. AFAIK the heat index takes into account the % humidity. Wet bulb and dry bulb makes

it sound like it's all or nothing - 0% humidity vs 100% humidity.

I think I'll just go grouse about it in the corner some more, lol.

[happyslug]

8. "Wet Bulb". I heard it in basic training in the 1980s

Sorry, when I was in Basic Training in 1981, every so often the command structure told us it was "Wet Bulb" i.e. to hot and humid to require us to run or do other physical activities. What the cut off was I was never told, but once it "hit" it went down the command structure to us, and we were merely recruits.

[hatrack]

5. Just a matter of time, really - central China's hot and humid as hell already anyway

And with trends accelerating, plus heat-island effect, not surprising.