I am a researcher that studies the interface between human heat stress and climate change. I list some news articles I was involved in and some peer reviewed manuscripts I coauthored below.
Tw at ~35°C (95°F), what does this mean? Putting it terms that may be more relatable, like the NWS Heat Index: whether at low or high relative humidity, a 95°F Tw is ~160°F Heat Index. A Finnish sauna (dry) temperature is ~160-190°F. However, a steam sauna is usually between 90-120°F, aka Tw of 90-120°F. Generally, you do not want to be in a steam sauna for more than 20 minutes, because it will very likely kill you. But, you do sweat a lot, and that can be quite relaxing, for short periods of time.
Tw 35°C is extremely rare in the outdoor environment. Persian Gulf/Pakistan area, if they occur (the veracity of those measurements are difficult to confirm). What happens more often (although, still quite rare) is Tw of 32°C (89.6°F). Heat waves, such as the Chicago 1995 (>700 dead) or the Indian-Paksitan Heatwave of 2015 (>2500 dead) peaked at those temperatures. Humans cease being able to function/perform labor at 32°C (89.6°F) Tw, regardless of the air temperature or humidity. And this is the real concern we have a climate scientists. Wet bulb temperatures peaking for extended periods of time (>6 hours) rarely exceed 28°C (82.4°F) today.
But, the major work that’s come out recently (some of it mine, but is also verified by independent statisticians), is that global maximum Tw is tied to global mean surface temperatures, and scales readily with global mean changes. In the tropics, this change is reliably projected to be ~0.9°C (1.6°F) Tw per 1°C (1.8°F) of global warming.
So, you can do thought experiments. At what point of global warming will there be sustained (>6 hours) of Tw at 32°C (89.6°F)?
Current max Tw at >6 hours is 28°C in the tropics:
Y = mx +b
b = 28°C (today)
Y = 32°C (future)
m = 0.9°CTw / 1°C global T change
x = (Y - b) / m
X = ~4.4°C global T change.
32°C (future) = (0.9°CTw / 1°C global T change) 4.4°C global T change + 28°C (today)
4.4°C change in global temperature is equivalent to ~8°F of global change.
This is a lot of global warming. But, not unlikely, given our current trajectories. Our estimate of global change by 2100 is about +4°C (7.2°F).
Cheers,
-Jonathan R. Buzan
PhD
Climate and Environmental Physics
and
Oeschger Centre for Climate Change Research
University of Bern, Switzerland
I am a researcher that studies the interface between human heat stress and climate change. I list some news articles I was involved in and some peer reviewed manuscripts I coauthored below.
Tw at ~35°C (95°F), what does this mean? Putting it terms that may be more relatable, like the NWS Heat Index: whether at low or high relative humidity, a 95°F Tw is ~160°F Heat Index. A Finnish sauna (dry) temperature is ~160-190°F. However, a steam sauna is usually between 90-120°F, aka Tw of 90-120°F. Generally, you do not want to be in a steam sauna for more than 20 minutes, because it will very likely kill you. But, you do sweat a lot, and that can be quite relaxing, for short periods of time.
Tw 35°C is extremely rare in the outdoor environment. Persian Gulf/Pakistan area, if they occur (the veracity of those measurements are difficult to confirm). What happens more often (although, still quite rare) is Tw of 32°C (89.6°F). Heat waves, such as the Chicago 1995 (>700 dead) or the Indian-Paksitan Heatwave of 2015 (>2500 dead) peaked at those temperatures. Humans cease being able to function/perform labor at 32°C (89.6°F) Tw, regardless of the air temperature or humidity. And this is the real concern we have a climate scientists. Wet bulb temperatures peaking for extended periods of time (>6 hours) rarely exceed 28°C (82.4°F) today.
But, the major work that’s come out recently (some of it mine, but is also verified by independent statisticians), is that global maximum Tw is tied to global mean surface temperatures, and scales readily with global mean changes. In the tropics, this change is reliably projected to be ~0.9°C (1.6°F) Tw per 1°C (1.8°F) of global warming.
So, you can do thought experiments. At what point of global warming will there be sustained (>6 hours) of Tw at 32°C (89.6°F)?
Current max Tw at >6 hours is 28°C in the tropics: Y = mx +b b = 28°C (today) Y = 32°C (future) m = 0.9°CTw / 1°C global T change x = (Y - b) / m X = ~4.4°C global T change.
32°C (future) = (0.9°CTw / 1°C global T change) 4.4°C global T change + 28°C (today)
4.4°C change in global temperature is equivalent to ~8°F of global change.
This is a lot of global warming. But, not unlikely, given our current trajectories. Our estimate of global change by 2100 is about +4°C (7.2°F).
Cheers, -Jonathan R. Buzan PhD Climate and Environmental Physics and Oeschger Centre for Climate Change Research University of Bern, Switzerland
Some News Articles: https://www.bbc.com/sport/olympics/57904094
https://www.theverge.com/2017/9/14/16290934/india-air-condit...
https://www.nytimes.com/2015/06/07/opinion/sunday/the-deadly...
Some Peer review manuscripts: https://iopscience.iop.org/article/10.1088/1748-9326/abeb9f
https://www.annualreviews.org/doi/abs/10.1146/annurev-earth-...
https://gmd.copernicus.org/articles/8/151/2015/