Wet Bulb at 33 C — Human Hothouse Kills Nearly 800 in Pakistan
Human-forced
warming of the global climate system is pushing sea surface
temperatures in some areas to a maximum of 33 C. Extreme ocean
warming that is increasing the amount of latent heat the atmosphere
can deliver to human bodies during heatwaves. And near a 33 C sea
surface hot zone, the past few days have witnessed extreme heat and
related tragic mass casualties in Sindh, Pakistan.
*
* * * *
For
Pakistan, the heat and humidity has been deadly. Temperatures over
Southeastern Pakistan hit 100 to 113 Fahrenheit (40 to 45 degrees
Celsius) during recent days. Night time lows dipped only into the 80s
and 90s (30s Celsius). Relative humidity throughout this period has
remained above a brutal 50% even during the hottest hours of the day.
Wet
bulb temperatures (the wet-bulb temperature is the temperature air
has if it is cooled to saturation — 100% relative humidity — by
evaporation) climbed into a dangerous range of 30 to 33 degrees
Celsius. This greatly reduced the ability of evaporation at skin
level to cool the bodies of human beings exposed to such oppressive
temperatures. As a result, people working outdoors, the elderly, or
those without access to climate-controlled environments fell under
severe risk of heat related injuries.
The
Hospital Morgue is Overflowing
According
to reports
from Al Jazzera, thousands
of heat injuries and hundreds of deaths have occurred across the
region since Saturday. Karachi’s largest hospital — Jinnah
Postgraduate Medical Centre (JPMC) — has been flooded with over
5,000 patients suffering from heat injuries since the weekend. At
some points, the hospital was receiving one heat injury patient per
minute — a pace that nearly overwhelmed the facility. By earlier
today, more than 380 of those patients had did.
Dr
Seemin Jamali, a senior official at JPMC noted to Al Jazeera:
“The mortuary is overflowing, they are piling bodies one on top of the other. We are doing everything that is humanly possible here. Until [Tuesday] night, it was unbelievable. We were getting patients coming into the emergency ward every minute.”
Across
Sindh, Pakistan the story was much the same with the total official
heat death toll now standing at 775 and climbing as calls were raised
for more government support for people impacted by the worst heat
wave to hit Pakistan in at least 15 years.
Killing
Heat and Unprecedented Rains
This
extreme and deadly heat is a feature of a boundary zone between a
hot, high-pressure air mass over the Persian Gulf region abutting
against a very moist and El Nino-intensified monsoonal system over
India. The result is a combination of high heat and high humidity —
factors that, together, are very hard on the human body (wet bulb
temperatures above 30 C are considered dangerous, while a blanket
measure of 35 C [never reached yet on Earth] is considered rapidly
deadly even in the shade).
During
late May and early June, similar conditions resulted in hundreds of
heat related deaths in India. When the heat finally abated, the
subsequent influx of monsoonal moisture set off torrential downpours.
In some places, rates of rainfall exceeded typical June monsoonal
accumulations by nearly 50 percent with Mumbai
already having received 32 inches of rainfall (normal
June rainfall is 23 inches). With Mumbai showing daily rainfall
accumulations of 1-3 inches, it is possible that June totals could be
double that of a typical year.
A
Ramping Oceanic Heat/Moisture Pump — Feature of a Record Warm World
The
high heat, high humidity and related extreme rainfall events are all
features of a warming world. At issue, primarily, is the impact of
human forced global warming on the ocean system and how this heating
then impacts the atmosphere — making it harder for humans to remain
alive outdoors during the most extreme heating events even as it
pushes a tendency for more and more extreme droughts and deluges.
This
warming related heat and moisture flux is most visible out in the
Pacific, where record global atmospheric and ocean heat is pushing
maximum sea surface temperatures into the lower 30s (typically
between 30 and 31 degrees Celsius). These high sea surface
temperatures in a record warm world are now dumping an extreme amount
of moisture into the atmosphere through an El Nino amplified
evaporation rate. A subsequent amplification of the equatorial storm
track due to extreme moisture loading has already seen extraordinary
record rainfall events in places as widespread as India, China and
the Central U.S.
(Sea
surface temperatures climb to near 33 C in the Ocean region near
Pakistan — supporting wet bulb temperatures [high heat and high
humidity] that generate a heightened risk of heat injury and death.
Image source: Earth
Nullschool.)
Maximum
global sea surface temperature is a good proxy measure for how much
moisture the atmosphere can hold, a measure that also likely
determines the maximum wet bulb temperature (implied latent heat) at
any given point on the globe. And particularly, near Pakistan, we
find ocean surface temperature readings in the range of 30 to 33 C
running through the coastal zone of the Indian Ocean and on into the
Persian Gulf. Readings that increased the amount of moisture the
atmosphere could hold at high temperature, increased relative
humidity readings as temperatures entered the 100s Fahrenheit (40s
C), and forced wet bulb temperatures into deadly ranges which in turn
reduced the ability of the human body to cool by evaporation at skin
level.
This
is how human-forced global warming kills with direct heat — by
basically increasing latent heat to the point that evaporation can no
longer cool the human body to a natural maintenance temperature of
98.6 (F) or 37 (C). And once wet bulb temperatures start hitting 35
C, then the heat casualty potential really starts to get bad —
essentially rendering heat wave regions temporarily uninhabitable for
human life outdoors. With maximum sea surface temperatures now
running near 33 C, we’re probably just within about 2 C of hitting
that deadly boundary.
The
Pakistan and Indian heat deaths this year, though extraordinarily
tragic and probably preventable without current level of human forced
warming of the atmosphere, serve as a warning. Keep warming the globe
through fossil fuel emissions and there are many far, far worse
heatwaves to come.
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