Increases in extreme humid-heat disproportionately affect populated
regions

Date:
October 13, 2021
Source:
Washington State University
Summary:
The world is not only getting hotter but also more humid and new
research shows people living in areas where humid-heat extremes are
already a significant hazard are bearing the brunt of the impact.



FULL STORY ==========================================================================
The world is not only getting hotter but also more humid and new research
by Washington State University scientists shows people living in areas
where humid-heat extremes are already a significant hazard are bearing
the brunt of the impact.


========================================================================== Their study, published earlier this month in the journal Geophysical
Research Letters, presents the timing, frequency, and severity of extreme humid-heat and dry-heat events and recent trends using hourly data at
a spatial resolution of ~ 25 km or 15.5 mi.

"We identify a greater increase in population exposure to humid-heat
as compared to dry-heat, emphasizing the importance of understanding
humidity changes in a warming world," said study lead author Cassandra
Rogers, a postdoctoral research associate in the WSU Vancouver School
of the Environment.

Most of Europe, northern South America, Africa, the Arabian Peninsula
and the island chains between the Indian and Pacific Oceans, as well
as the Northern Hemisphere oceans, have experienced statistically
significant increases in both dry and humid-heat extremes, according to
the researchers' analysis.

However, a few regions of the planet showed trends that are particularly worrisome.

"For example, increases in the occurrence of humid-heat were strongest
over highly populous regions in South and Southeast Asia and southeastern
U.S. where changes in dry-heat frequency, as measured by temperature
alone, are small or non-significant," said study coauthor Deepti Singh,
an assistant professor in the WSU Vancouver School of the Environment.



========================================================================== Rogers and Singh's work suggests that increasing irrigation intensity
could be increasing humidity and consequently extreme humid-heat, since
a large fraction of land-area in these regions is croplands and the
timing of high irrigation rates over places like India coincide with
the warmest temperatures.

The consequences could be severe unless efforts are taken to reduce the
impact on vulnerable workers.

"With many areas in these regions already approaching the survivability
limit of heat and humidity, manual, labor-intensive outdoor work such
as agricultural activities, construction and pulled- or cycle-powered
rickshaw transport could effectively become infeasible during the hot
parts of the day for much of the year," Rogers said.

Given the higher-population exposure to humid-heat and its projected
increases, particularly in vulnerable areas, the researchers' findings emphasize the need to better understand their societal impacts.

This could be done by considering the timing of how such extremes
intersect with the timing of location-specific human activities,
demographics, and socio- economic factors that enhance vulnerability to
heat stress.



==========================================================================
In the future, developing a greater understanding of the human
health effects of humid-heat stress will be of particular importance
to communities with vulnerable workers that are directly exposed to
extreme heat, such as farm and urban outdoor laborers as well as people
with limited access to air conditioning, electricity, community cooling
centers and health and emergency medical services.

"Addressing the socio-economic factors and infrastructure issues through policy, adaptation measures or financial aid can help reduce the severe
health impacts of committed climate change," Singh said.

In addition to Rogers and Singh, the research team for the study included scientists from Syracuse and Columbia Universities in New York and NASA's
Jet Propulsion Laboratory in California.

Their work for the project includes data from weather stations on every continent as well as another climate dataset -- ERA5 reanalysis --
that provides hourly weather conditions across the entire world for
the past 42 years. The ERA5 data have not previously been used to study humid-heat extremes.

By synthesizing multiple observation sources, including weather stations,
ocean buoys, and satellite data, the newly available ERA5 data have
allowed the researchers to examine heat extremes over all land and ocean regions, including many previously poorly observed and studied locations.

"Our study extends previous research to provide information on changes
in dry and humid-heat extremes for understudied regions of Africa,
Southeast Asia and South America, where reliable, long-term, station
data is limited," Singh said.

"Further, we show that strong increases in extreme heat
frequency are accompanied by an expansion of the number
of months during which they occur, which has consequences
for human health and outdoor activities in these regions." ========================================================================== Story Source: Materials provided by Washington_State_University. Original written by Will Ferguson. Note: Content may be edited for style and
length.


========================================================================== Journal Reference:
1. Cassandra D. W. Rogers, Mingfang Ting, Cuihua Li, Kai Kornhuber,
Ethan D.

Coffel, Radley M. Horton, Colin Raymond, Deepti Singh. Recent
Increases in Exposure to Extreme Humid‐Heat Events
Disproportionately Affect Populated Regions. Geophysical Research
Letters, 2021; 48 (19) DOI: 10.1029/2021GL094183 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/10/211013104635.htm

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