Friday, 24 June 2016

Wet bulb termparatures in India

The Increasingly Dangerous Hothouse — Local Reports Show It Felt Like 160 F (71 C) in India on June 13th, 2016

23 June, 2016
The climate change induced delay of India’s monsoon is a pretty big deal. Not only does it reduce the amount of moisture — necessary for the provision of life-giving crops for this country of 1.2 billion — provided by the annual rains, it also increases the potential for life threatening heatwave conditions. And according to local reports, some of the highest heat index values ever recorded on the face of the Earth were seen in Bhubaneswar, India during a period of record heat and high humidity as the Asian Monsoon struggled to advance.
The Indian province of Odisha sweltered under high heat and humidity that may well have represented the most miserable conditions ever recorded on Earth at any time or place on June 12th and 13th of 2016. Cooling monsoonal rains should have arrived over this eastern section along the Bay of Bengal by that time. But this year, the rains were delayed by about a week and were still about 5 days away. The heat was firmly entrenched. A great wall that seemed to fend the monsoon off.
India Monsoon 2016
(The India Monsoon is finally starting to catch up. After being delayed by 1-2 weeks during early June, the monsoon is now on time for some locations even as it still delayed by 5-7 days for parts of western India. The early June delay, however, has probably lowered overall moisture content of the monsoon even as it contributed to record heat index and wet bulb readings for sections of Odisha on June 12 to 13. Image source: India Meteorological Department.)

As the frontal edge of the monsoonal flow began to run into a region of high temperatures over Odisha, humidity levels spiked even as temperatures remained high. On the 12th and 13th of June, 2016, thermometers topped out at between 101 F (38 C) and 109 F (43 C) even as humidity levels rose. This combination generated a spike in what is called the Misery Index (or an indicator of how hot if felt to be outside). And it also, apparently, pushed wet bulb temperatures in some areas to record levels for any place on Earth.
Wet Bulb at 38 C?

For an unconfirmed report out of Bhubaneswar indicates that temperatures on June 13th hit 103.5 F (39.7 C) even as relative humidity readings were at 87 percent. That’s a wet bulb reading of 37.6 C. And if this report is true, that means it felt like 160 degrees Fahrenheit or 71 degrees Celsius for a brief period in Bhubaneswar that day. If so, this would be near the highest Misery Index value ever recorded on the planet — just a hair below last year’s peak measure in Iraq of a 163 F or 73 C heat index (38.4 C wet bulb) reading. And outright crushing periods during 2015 when India’s wet bulb measures in Andhra Pradesh hit 30 C.

(According to Earth Nullschool, it felt like 41 to 54 C [104 to 127 F] outside over Eastern India on June 12th and 13th of 2016 due to combined high levels of heat and humidity. Local reports from Bhubaneswar indicate that this Misery Index hit a stunning 71 C [160 F] on June 13th. Image source: Earth Nullschool.)

A wet bulb measure is a kind of thermometer for latent heat in the atmosphere. It uses a wet bladder to measure the temperature of a membrane at the point at which water evaporates. It’s meant to simulate the lowest temperature the human skin can reach through evaporative cooling as the body sweats. The higher the combined heat and humidity, the higher the wet bulb temperature and the hotter it feels. We’ve all experienced this when stepping outside on a day during which both the temperature and humidity are high. And we intuitively know that it’s the combination of heat and atmospheric moisture that makes hot days feel even more oppressive.

It’s a combo that’s also dangerous to human health. At a certain point, the human body becomes unable to cool itself by sweating. And this level of latent heat at which the human body becomes incapable of transporting heat away from the skin is a wet bulb reading of 35 degrees Celsius.
Wet bulb readings do not need to hit 35 C to risk loss of life and heat injury. Wet bulbs above 25 C are considered dangerous and readings for extended periods near 30 C have resulted in mass injury and loss of life in places like Europe during the early 2000s, in Chicago during 1995 and in India during 2015 and 2016. However, exceeding wet bulb readings of 35 C over extended periods of time is an extraordinarily dangerous event. It’s also a new hazard related to human caused climate change. For last year was the first time a wet bulb reading above 35 C was ever recorded on the face of the Earth. And the 2016 37.6 C wet bulb reading for Bhubaneswar, if it bears out, is an extraordinary measure.

Readings this high over large regions over any extended period would make staying outdoors without access to cool water or climate controlled environments unlivable for human beings. And a human forced warming of the world by fossil fuel burning appears to now be in the process of bringing those conditions about. A condition of dangerous added latent heat to the atmosphere that has caused some scientists to sound the alarm that a global hothouse emergency is already upon us. And that unless a massive curtailment of fossil fuel burning takes place soon — large sections of the Earth’s surface will be rendered uninhabitable to human beings due to atmospheric latent heat content alone.

For as ocean surface temperatures rise, more moisture is pumped into the atmosphere in the form of humidity. This extra humidity hits regions of airs that have already been warmed to much higher readings by the over-burden of heat trapping gasses, like CO2, in the atmosphere. The result is a higher latent heat content of the airs of the Earth, and the breaching of wet bulb readings that are deadly to human beings who lack access to climate controlled environments.
UPDATED 11:00 PM EST, June 21
Hat tip to Wili
Hat tip to Colorado Bob
Hat tip to Scott

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