| NEW YORK, June 24
NEW YORK, June 24 The old adage, "it's not the
heat, it's the humidity," will come into play more often and in
more places because of climate change, with life-altering
results in southern U.S. cities from Miami to Atlanta to
Washington and even northern ones such as New York, Chicago and
"As temperatures rise, toward the end of the century, less
than an hour of activity outdoors in the shade could cause a
moderately fit individual to suffer heat stroke," said
climatologist Robert Kopp of Rutgers University, lead scientific
author of the report. "That's something that doesn't exist
anywhere in the world today."
That result emerges from the heat-and-humidity analysis in
"Risky Business," the report on the economic consequences of
climate change released on Tuesday. The analysis goes beyond
other studies, which have focused on rising temperatures, to
incorporate growing medical understanding of the physiological
effects of heat and humidity, as well as research on how and
where humidity levels will likely rise as the climate changes.
The body's capacity to cool down in hot weather depends on
the evaporation of sweat. That keeps skin temperature below 95
degrees Fahrenheit (35 Celsius). Above that, core temperature
rises past 98.6F. But if humidity is also high, sweat cannot
evaporate, and core temperature can increase until the person
collapses from heat stroke.
"If it's humid you can't sweat, and if you can't sweat you
can't maintain core body temperature in the heat, and you die,"
said Dr Al Sommer, dean emeritus of the Bloomberg School of
Public Health at Johns Hopkins University and author of a
chapter on health effects in the new report.
The highest heat-plus-humidity reading in the United States
was in 1995 in Appleton, Wisconsin, when the outside temperature
was 101F. While the Upper Midwest is not known for tropical
conditions, climate research shows that it will experience more
warming than lower latitudes as well as more humidity.
As a result, the deadliest heat-and-humidity combinations
are expected to center around that region, with threads reaching
to the Eastern Seaboard and islands of dangerous conditions
along the northwest Pacific coast.
If climate change continues on its current trajectory, the
report concluded, Midwesterners could see deadly
heat-and-humidity pairings (which meteorologists call "wet-bulb
temperature") two days every year by later this century.
"It will be functionally impossible to be outside, including
for things like construction work and farming, as well as
recreation," said climate scientist Michael Oppenheimer of
Even without killer humidity, heat waves are expected to
take a larger and larger toll.
The Southeast is expected to be hit with an additional 17 to
52 extremely hot days per year by mid-century and an additional
48 to 130 days by 2100. That could prove deadly for thousands:
"Risky Business" projects an additional 15 to 21 deaths per
100,000 people every year from the heat, or 11,000 to 36,000
additional deaths at current population levels.
(Editing by Douglas Royalty)