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Miserably Hot in Mid-Atlantic? There’s a Reason for That.

High heat index values continued across parts of the Mid Atlantic today with heat index (feels like temperatures) above 100 for many locations. A front, fortunately, is expected to bring some relief by this weekend.

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Western Heat Predicted to Move East

The extreme heat that is helping to fan severe western wildfires from California to Alaska is predicted to move eastward over the coming days. This shift is expected to set off high temperatures in the 90s and 100s from the Gulf Coast all the way to the Great Lakes and into the Northeast. Heat Index values, meanwhile, are predicted to spike into the 100s and 110s from the Mississippi Valley north and eastward.

(Much warmer than normal temperatures spread from west to east across the U.S.)

These much warmer than normal temperatures and potentially dangerous heat index values occur in a context of larger national and global warming. May of 2018 was the hottest on record according to NOAA. The U.S. presently sits between two warmer to much warmer than normal ocean zones. And overall global temperatures have been rising since the 1900s, with a more rapid up-ramp occurring since the late 1990s.

For the Central and Eastern U.S., warmer than normal oceans are also spiking atmospheric moisture levels through increased rates of evaporation. These higher moisture levels will be contributing to predicted heat indexes where large regions are expected to experience temperatures that feel like the 100s or 110s (see image below).

(Heat index values are predicted to rise to between 40 and 45 C for large parts of the Central and Eastern U.S. The 44 C predicted heat index for parts of Western New York on July 1 corresponds to a 111 F ‘feels like’ condition for this Northeastern region. Such high heat index values present a heightened risk of heat injury due to long term exposure. Image source: Earth Nullschool.)

Combined high heat and humidity increase the risk of heat injury due to exposure. And rising heat indexes and wet bulb temperatures are just one of the many potentially harmful aspects of human caused climate change.

From Inverse:

In the future, parts of the world will become so hot and humid that healthy adults sitting in the shade will die within a matter of hours. It’s hard to imagine, and yet that’s where Earth’s climate is headed, perhaps sooner than expected.

But while many recent studies have rightly focused on physical human limits under high wet bulb temperature risks for parts of South Asia and the Middle East, the Central to Eastern U.S. is also a region of concern. Climate risks to this region of the U.S. are due to both high predicted temperatures and high moisture levels from increasingly warm Gulf and Atlantic Ocean surfaces. The result is that heat capable of resulting in rapid heat injury or even loss of life, with wet bulb temperatures above 35 C, is possible by mid-to-late Century under high fossil fuel burning scenarios.

(At 10 C global warming, large regions of the world are regularly predicted to experience temperatures above 35 C Wet Bulb readings — or a level at which the human body is not naturally capable of cooling itself. Of course, such dangerous Wet Bulb readings are possible under still lower levels of global warming. Note that the Central to Eastern U.S. is one of the indicated hot spots from this recent paper.)

Though the Eastern U.S. is not yet facing extreme wet bulb readings of this kind, temperatures and humidity levels are presently on the rise. So the predicted heat wave is still expected to pack a punch. And perhaps a bit more than we’re used to.

We’re looking at a predicted extended period of significant above normal temperatures and high humidity over the coming days. So the public should stay tuned to local media for heat advisories issued by the National Weather Service (see heat safety tips here) and do what they can to keep cool by drinking water frequently and by spending less time exposed to blazing temperatures and sweltering humidity.

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

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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.

image

(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

Links:

India Meteorological Department

Odisha Sizzles Under High Heat and Humidity

Odisha Continues to Sizzle Under Heat Wave

Earth Nullschool

Understanding Wet Bulb Temperatures

Dr. James Hansen: We Have a Global Emergency

Hat tip to Wili

Hat tip to Colorado Bob

Hat tip to Scott

Dangerous Heat Sets Sights on Southern United States

High wet bulb temperatures and related heatwave mass casualty events have spanned the globe during the record hot summer of 2015. Now, it appears the Southern United States is also falling under the gun of life-threatening heat and humidity.

Gulfs of Mexico, California Host Screaming Sea Surface Temperatures

As with so many recent heatwaves with the potential to produce mass casualty events, the story starts with sea surface temperatures in excess of 30 degrees Celsius (86 Fahrenheit). And across a broad region of the Gulf of Mexico and all throughout the Gulf of California ocean surface waters now feature temperatures in the range of 30 to 33 degrees C (86 to 91 F).

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(A tell-tale pool of 30 C+ water is gathering in the Gulfs of Mexico and California. Such hot water is a support for deadly wet-bulb readings in the range of 30-33 C. Image source: Earth Nullschool.)

These are waters warmed by increasingly vicious human hothouse conditions. A world ocean facing a global fever that is 1 degree C (1.8 F) hotter than the more placid, less dangerous temperatures of 135 years ago.

In the Gulfs of Mexico and California, this heat has concentrated — pushing the waters there into 1-4 C above average ranges. Generating a dangerous reservoir of latent heat. One featuring ocean temperatures similar to those that kicked off heatwave mass casualty events in India, Pakistan, Japan and Egypt this summer. But this feature of the human hothouse is now focusing in on the Southern US — creating conditions that are increasing the risk of heat stress, heat injury and possibly loss of life.

The steaming waters of our southern gulfs will feed dangerously high wet bulb temperatures throughout a large region from the Carolinas to Florida through the Gulf States and on into the Southwest over the coming days and weeks. Ocean temperatures hot enough to support wet bulb readings in the range of 30 to 33 degrees Celsius. Dangerous levels very close to the maximum human threshold of 35 C.

NOAA Predicts Heat Indexes to Skyrocket

Concordantly, a similar measure used to determine how hot it feels outside is set to skyrocket throughout the southern US over coming days. In many regions heat indexes are predicted to exceed 100, 105, 115 or even 120 degree readings.

High Heat Index US South

(Forecast heat index map for Monday, August 24. Over the next seven days, heat index values are predicted to remain in dangerous ranges across large sections of the Southern United States. Image source: NOAA.)

Regions at greatest risk include Southern California, Arizona, and the Gulf Coast states of Texas, Lousiana, Mississippi, Alabama, Georgia and Florida.

Heat index values in excess of 105 F (40 C) are considered dangerous. Those crossing a 127 F (53 C) threshold are considered exceedingly dangerous. The NOAA forecast now includes dangerous heat indexes predicted for the above regions lasting for at least the next seven days. And with sea surface temperatures likely to remain much hotter than average near the area of highest impact through the end of August, these high-risk heat conditions have the potential to continue for some time.

Links:

NOAA

Earth Nullschool

Heatwave Mass Casualty Events of 2015

Wet Bulb

Heat Index

Hat tip to DT Lange

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